§ Introduction
§ Siting
§ Workers
§ Construction site
§ Construction yard for Production of houses
§ Design/ Layout
§ Process-based design
§ Work with local community
§ Desires of community primary
§ Overview of systems approach to design
§ General over-arching concerns
§ “Patterns” based on local culture (see A Pattern Language)
§ Utilizing assessment materials
§ Food, bathroom use, etc.
§ Be sure to talk to the women!
§ Circulation
§ Weather protection
§ Protection against natural disaster
§ Security
§ Affordability
§ Maintenance
§ Energy-efficiency
§ Passive solar
§ Basic ideas on how rooms can best go together for efficient planning
§ New buildings
§ Add-ons/repair of existing
§ Materials
§ Foundations Options and Drainage
§ Earthbags
§ Wall Systems
§ Straw bale Construction
§ Cob Construction
§ Adobe Construction
§ Others
§ Doors and Windows
§ Roofs, Ceilings and Insulation
§ Plasters and Finishes
§ Floors
§ Utilities
§ Landscaping
§ Tool and Material List
Introduction to Locally-Appropriate Building
What is “locally-appropriate?
§ Local materials
§ Native skills
§ Promotes cultural continuity
§ Sustainable
§ Based on principles of “natural building”
What is natural building?
§ “Any building system which places the highest value on social and environmental sustainability” Michael Smith
§ Minimizes ecological impact
§ Healthy, beautiful, comfortable, spiritually uplifting and inexpensive
§ Utilizes easy-to-learn techniques and locally available renewable resources
§ Human labor and creativity instead of capital, high technology and “experts”
§ Regionally appropriate
§ Depends on local ecology, geology and climate, building site, and needs and personalities of builders and users
§ Not a new idea – rediscovering ancient techniques and applying them to our modern living situations
Environmental Impact
§ Building industry is a major contributor to environmental problems
§ Deforestation, mining, greenhouse gases, energy and water use – all from building construction and use
§ Most natural building materials are biological by-products, or minimal impact mined minerals – these are low-embodied energy materials
§ Natural builders try to minimize and localize damage
§ Use of local natural materials reduces dependence on manufacturing and transport industries
§ Use of recycled materials to reduce pollution, turn waste into a resource.
Human Health
§ Modern buildings are making many people sick. Toxic materials in buildings that don’t “breathe”
§ Natural buildings are life enhancing
§ Modern buildings – artificial angles and colors – may be detrimental to psychological health
Social Justice
§ Modern building industry takes the power to build houses out of the hands of people
§ 1/3 of the world’s population is homeless or in substandard housing
§ Current building codes reduce options – leading to higher costs
§ We think we have to pay experts – architects and builders a lot of money for a big house
§ There is a great need for affordable housing
§ New options which utilize local materials and owner’s labor can bring down costs, especially in labor-rich countries
§ Natural builders advocate small houses which use passive-solar techniques for heating and cooling
§ A small low-cost house provides more time for family, friends and creativity
§ Natural building creates a different social dynamic than conventional construction
§ Whole family can get involved
§ Natural building worksites can be safe places for children
§ Building a natural building with friends builds community as well
§ Natural buildings reduce our impact on the environment – frees up resources for the less-privileged and future generations
§ One of the most critical design decisions
§ Difficult to correct a bad siting decision once building is built
§ Best to spend a lot of time on building site to determine weather patterns, special spots, sun patterns, etc. Ideally one full year to experience the seasons
§ Do research – speak to neighbors, consult historical records etc.
§ Slope – A sloped site can help drain water and air. Gravity can help with many common household needs (moving water, etc.) Excavation can provide building materials
§ Aspect – South facing slopes (northern hemisphere) are best for buildings (opposite in southern hemisphere)
§ Drainage – well-drained soils are best. Stay away from seasonal creeks and gullies
§ Subsurface geology – dig a lot of test holes to see what is there
§ Proximity to water (potable)
§ Proximity to growing areas
§ Potential
§ Do not build on good agricultural soils
§ Existing
§ Solar access – make sure sun can hit your building from the south (north in southern hemisphere)
§ Shade – shaded areas are best on southwest (northwest in southern hemisphere), west parts of site. Deciduous trees or vines shade in summer but let in light in winter
§ Prevailing winds – find out which directions storms and pleasant breezes come from (can be different in different parts of day/ year)
§ Air drainage – avoid low spots (frost hollows) where cold air collects
§ Fire – avoid ridges or hilltops
§ Floods – stay above “worst-case” flood zone
§ Master planning – how does your building fit into existing and future development
§ Access – how will you get yourself, materials to site
§ Water and utilities – determine how will you get them to site, how you will remove/treat wastes
§ Building materials – determine where they will come from. Consider using local materials as much as possible. Store near site, on “uphill” part if possible to make transport easier.
§ Zoning and regulations – find out land use near you, zoning restrictions. Develop good relations with neighbors
§ Privacy – visual, noise, smells, light
§ Security – from natural and social stresses
§ Community – isolated or near others
§ Easements – when someone else has permission to do something on your property
§ Future development – check with local planning department
§ Views
§ History – archeological, cultural, toxic uses in past
§ Ecological impact – determine the habitats of other species
§ Consider building on “worst” part of site (most disturbed/impacted) for ecosystem rehabilitation
§ Feng Shui/ Intuitive placement
§ Chinese art of placement (known as “geomancy” in the west)
§ Intuitive sense of what “feels” right
§ Don’t build on most “magic” spots
§ Staying put – consider staying where you are and improving where you already live
§ Renovation of existing structures
§ Often the most desired option
§ Commutes – sites with long transportation commutes will outweigh any energy savings in buildings
§ Available resources – are good building materials on site?
§ Remoteness – building in remote areas can disrupt wilderness and lead to further development
§ Size – determine smallest “destruction zone” you can manage
§ Rope off fragile areas during construction
§ A smaller house saves energy and resources too
§ Work with local community
§ Desires of community primary
§ Work with rough models, sketches, mockups
§ Reduce reliance on highly-detailed “plans”
§ These can be produced once good design is determined for reference
§ Consider all aspects at once
§ Planning thoroughly early on to avoid costly mistakes
§ Flexible design “philosophy” to fit local needs and conditions
§ Wise choices of materials and design to save energy
§ Good construction – so lasts as long as possible
§ Solves more than one problem at a time, does not create any new ones
§ Works well at all levels, not just a few
§ Creatively works with local skills and resources
§ Improves balance and harmony
§ Is flexible
§ Open to future renovation/ addition
§ Uses land appropriately, reduces destructive activities
§ Uses resources efficiently
§ Supports human health through choice of materials and methods
§ Strengthens the local economy and supports the community
§ Conserves the Biosphere
§ Protects agricultural sites, cultural resources, and archeological remains
§ Creates nice places to live
§ Creates buildings which are inexpensive to build and operate
§ “Patterns” based on local culture (see A Pattern Language)
§ Utilize assessment materials to determine
§ Work these out extensively with local people
§ Do not make assumptions
§ Food, sleeping, bathroom use, etc.
§ Be sure to talk to the women!
§ Circulation
§ Weather protection
§ Protection against natural disaster
§ Structural considerations
§ Security
§ Affordability
§ Maintenance
§ Energy-efficiency
§ Passive solar
§ Basic ideas on how rooms can best go together for efficient planning
§ Nice detailing
§ Integration of indoor and outdoor space
§ How done is dependent on climate
§ Examples: Hot/dry – courtyards
§ Hot/humid - verandas
§ Different strategies for each type
§ Residential
§ Commercial
§ Industrial
§ Transitional
§ Temporary
§ “Ecological design” is one such approach
§ Basic Ecological Principles
§ Systems
§ Flows and cycles
§ Waste equals food
§ Carrying capacity
§ Design Principles
§ Solutions grow from place
§ Ecological accounting informs design
§ Design with nature
§ Everyone is a designer
§ Make nature visible
§ Healthy for people and planet
§ Non-toxic materials
§ Less destructive to the ecosystem
§ Healthy indoor environment
§ “Restorative” design helps improve degraded ecosystems
§ Ecologically-designed homes ideally produce own energy and food, collect clean air and water
§ Solutions grow from place
§ More here
§ Ecological accounting informs design
§ More here
§ Design with nature
§ More here
§ Everyone is a designer
§ More here
§ Make nature visible
§ More here
§ Determine overall program
§ Identify cultural/spiritual components of design
§ Determine “program” (use assessment data)
§ Based primarily on desires of local people
§ Daily activities
§ Be sure to acknowledge desires for status, cleanliness, modernity, etc.
§ Creatively use local materials to satisfy these desires
§ Create sketches, model and/mockups, work on site as much as possible
§ Satisfy any code requirements – work with, not against code officials
§ Climate – determines shape of house
§ Hot/dry or cold – compact
§ Conserves energy
§ Hot/humid – more spread out
§ Allows for cooling breezes
§ Also determines foundation/wall/roof/finish choices
§ Main rooms to the south (north in southern hemisphere)
§ Small efficient plan
§ Simple layout for ease of construction
§ Design to the module of materials at hand
§ Building materials
§ Reduce, reuse, recycle
§ Designs which can be readapted easily
§ Import materials from closest source
§ Use materials low in embodied energy
§ Life cycle analysis
§ Pay attention to building site – reduce impact on animals and plants
§ Energy efficiency
§ Good insulation
§ Passive solar design
§ Good use of local energy resources
§ Wind, solar, hydro, etc.
§ Cooling – awnings, trellises, trees
§ Minimize west windows, create proper south overhang (north overhang in southern hemisphere)
§ Natural ventilation – cool towers, evaporative cooling, roof vents
§ Natural insulation – growing plants on outside of building
§ Use north side of building for cool storage
§ Thin buildings in hot humid climates for good cross-ventilation
§ Passive solar design
§ Place most of windows towards south (north in southern hemisphere)
§ Overhang blocks summer sun, lets in winter sun
§ Long thin house with big bank of south windows maximizes solar gain
§ Use thermal mass where sun hits to absorb and store heat (bricks, earth, adobe, etc.) Water stores heat too.
§ Attached greenhouse
§ Can add humidity to house
§ Trombe wall
§ Not so much of an issue in hot/humid climates
§ Additional Heat Sources
§ Efficient stoves/ovens
§ Provide proper combustion air/ venting
§ Radiant floor/wall heating
§ Fireplaces are not very efficient heaters but nice socially and experientially
§ Helps keep temperature in the house even
§ Most important in roofs, then walls and floor
§ Avoid large skylights – major heat gain in summer, heat loss in winter
§ Natural insulation – cellulose, wool, cotton, straw
§ Reflective foil for undersides of roofs, roofs can be painted white for added reflection
§ But be aware of glaring light for neighbors
§ Thatched roof are good insulators
§ Make north wall particularly well-insulated (south in southern hemisphere)
§ Seal windows, doors against drafts
§ Window insulators – double-glazed windows, insulated curtains on inside, shutters on outside
§ Make sure fireplace has a damper, combustion air comes from outside
§ Many modern materials give off toxic fumes
§ Sick building syndrome
§ Multiple chemical sensitivity
§ Use non-toxic building materials, paints, carpets, cleaning products, etc.
§ Metal in buildings – negative effects of electromagnetic waves
§ Make sure to ground metal in building to earth
§ Renovation
§ Temporary Structures
§ Local availability
§ Natural
§ Recycled
§ Locally manufactured
§ Strength
§ Durability
§ Properties
§ Tensile capacities, etc.
§ Aesthetics
§ Cultural value
§ Symbolic value
§ Ease of workmanship
§ What is “natural?”
§ One definition – that which is closest to the state found in nature
§ Non-harmful to humans and to the ecosystem
§ Natural builders use some “non-natural” materials with particularly useful or non-replicable properties as well (i.e. waterproof membranes, concrete in foundations)
§ Ecological impact
§ Availability
§ Workability
§ Embodied energy (energy needed to produce and transport a given amount of material)
§ Impact of harvest/extraction from ecosystem
§ Composed of stones, gravel, sand, silt, clay and organic material
§ Stones largest-sized component, clay the smallest
§ Best earth for building – 20-30% clay, 70-80% sand
§ Building techniques which use earth – rammed earth, adobe, cob, earthbags, pressed earth blocks
§ Used for thousands of years. At least 1/3 world’s population live in earth houses
§ Strong in compression, weak in tension
§ Needs special protection from water and earthquakes
§ Sedimentary, igneous or metamorphic
§ All earth materials were originally stone
§ Igneous stone
§ Formed by cooling of liquid magma
§ Some has air bubbles making it a good insulator (pumice)
§ Sedimentary stone
§ Sediments from erosion by wind or water cemented together by pressure and time
§ Layered – splits easily into flat pieces
§ Metamorphic stone
§ Igneous or sedimentary stone altered by heat, pressure or chemical weathering
§ Usually a good wall building material, splits easily into blocks
§ Best stone for building – angular with flat parallel sides
§ Stone makes excellent foundations
§ Thin flat stone can be used as a roofing material (slate)
§ Can be expensive and labor intensive to build with stone, but lasts a very long time
§ Is comprised of small stones
§ Useful for lining drainage trenches and for creating rubble-trench foundations
§ Can be used to fill bags for a “low-tech” foundation – keeps water from wicking
§ Is an essential ingredient of concrete
§ Can form an ingredient in cob
§ Is small gravel
§ Essential material for earthbuilding techniques (with clay) and concrete
§ Angular sand best, but this type is often created by destructive mining practices
§ Fine rounded sand good for finish plasters
§ Smallest soil particle
§ Weathered from the mineral feldspar
§ Is composed of flat plates that stick well to themselves and each other
§ Essential as a binder in earthbuilding
§ Does not react well with cement
§ To find – notice clumpy soils, or soil with a lot of cracks
§ Bricks are formed from clay on are then baked in a kiln
§ The higher the temperature they are baked, the harder they become
§ Bricks come in many shapes and sizes
§ Commonly used in walls but can also be used for floors or vaulted roofs
§ Flat thin element made from fired clay (curved tiles often used to form roof surfaces)
§ Used to create a hard, waterproof surface
§ They come in many different colors for decoration
§ Usually attached to a base material which is structurally strong (stone, concrete)
§ Used for floors, wall surfaces, counters and roofs
§ Tile roofs are excellent for catching rainwater
§ Is the interwoven roots of grass and the soil they capture
§ Can be cut into bricks and stacked like adobes
§ Placed on roofs to create a “living roof”
§ Comes from the harvesting of trees
§ Not all trees are good for building
§ Strong in compression, tension and bending
§ Lightweight, renewable, benign, flexible, forgiving, easy to build with
§ Little energy needed to process it and transport it
§ Can be used for posts, beams, floors, roofs, windows, doors, furniture and wall coverings
§ Must be used wisely to help decrease deforestation
§ Engineered timber created by gluing smaller pieces of wood together to form specially-shaped or sized members
§ Can be used to form walls – low insulation
§ Can also be used like bricks in cordwood construction
§ Logs “in the round” are stronger than milled lumber of the same cross-sectional size
§ I the thick layer of reeds, grass, straw or palm leaves used as a roofing material
§ Hollow stemmed water plants
§ Sheds water well, straight and long
§ Some reeds can be used to create structural roofs (vaults)
§ They are a lot of work to harvest, are of limited availability
§ Hollow stemmed stalk of cereal grains and grasses
§ Can be baled into large blocks and stacked to create walls
§ Used loose or fine as an additive to many earthbuilding mixtures
§ If long and strong can be used for thatch
§ Adds tensile strength, resistance to cracking, insulation value, increased workability of earthen materials
§ Not a natural material per the above definition but used by many natural builders
§ Made of sand, gravel, water lime and Portland cement
§ Pozzolans (rice hull ash, fly ash, brick dust) can be used to replace some cement in concrete (as well as cement plasters)
§ Mixed wet and poured into forms
§ The less water used, the stronger the concrete
§ Can also be sprayed dry and wetted at the nozzle to form walls etc. (gunnite)
§ Solidified and cures over time
§ Is kept wet while it cures for increased strength
§ Very high in compressive strength
§ Needs reinforcing to resist tension
§ Can be used in foundations, walls, roofs, etc.
§ However, very high in embodied energy
§ Difficult to recycle
§ If cut into uniform slabs can be cemented together like stone to form foundations/walls
§ Iron and carbon – harder and more flexible than iron
§ Used for metal roofs, reinforcing and structural members (not recommended for the “Faraday cage” electromagnetic effect which some believe can effect health)
§ High in embodied energy but easily recycled
§ Largest of the grasses
§ “Culms” (stalks) used in construction
§ Strong in tension and compression, weak in bending
§ Grows very quickly and can replace wood in many applications
§ Needs appropriate design details for long construction life
§ Most common in the tropics
§ Traditional binder made from limestone or seashells
§ Mixed with sand for plasters and mortar
§ Limestone is burned then crushed, then mixed with water (slaking) to make lime putty
§ Lime putty is best lime for building. Strongest in this form. Gets better stored over time.
§ Dried hydrated lime is much inferior
§ High embodied energy, but possibility for local manufacture
§ Softer and more flexible than cement
§ Breathes
§ Can be pulped and mixed with clay or cement to make blocks
§ Powdered paper makes good insulation
§ Used to make bags or for surface decoration
§ Reusing old doors, windows, etc.
§ “Trash” can be used in innovative ways, i.e. tires, bottles, cans, etc.
§ Entire buildings can be reused instead of torn down. Saves embodied energy of original manufacture
§ Cow manure best
§ Used to make fine plasters
§ Fresh manure can be used to create floors
§ Be careful in using fresh manure to avoid pathogens
§ Added to earth or lime mixtures to increase hardness, preservation, workability, or waterproofness
§ Includes: eggs, milk, blood, urine, oils, cactus juice, starch, tallow, sap, flour and molasses
§ Sticky test – rub paste between fingers. If it feels tacky it has clay. The tackier it is the more clay it has.
§ Ribbon test – make a rod the size of a pencil. Wrap it around your finger. The less it cracks, the more clay it has
§ Clumpy soil is usually clay
§ Soil with lots of cracks when dry is usually clay
§ Collect subsoil samples. Break up large clumps. Clumpy soils should be crushed to a powder
§ Place in a straight-sided clear jar
§ Add water and a pinch of salt to help clay settle
§ Shake jar
§ Wait a few minutes, then shake jar again
§ First five seconds of settling – all sand and gravel will have settled out. Mark side of jar at this point
§ Five seconds – ten minutes – all sand and silt will have settled. Mark the jar at this new layer.
§ If water is clear at this point there is no clay
§ When all is settled mark the final clay layer and determine proportions.
§ It is important to mark the layers as they settle as it is sometimes difficult to distinguish between the silt and clay layers
Drop test (for cob)
§ Shape your proposed building mixture into a small ball.
§ Throw the ball in the air and catch it in your hand
§ If it flattens there is too much clay or water
§ If it cracks apart there is too much sand or not enough water
§ If it keeps its shape it is good to build with
Crunch test (for cob)
§ Hold mixture to your ear and squeeze it
§ You will hear a “crunching” sound from the sand grains moving against each other which indicates that you have enough sand in the mix
FOUNDATIONS AND DRAINAGE
Purpose of foundation
§ Spreads load
§ Holds building together as one unit
§ Raises wall above water
Foundation choice determined by
§ Site considerations
§ Soil characteristics
§ Seismic considerations
§ Building type
§ Load type (point or evenly distributed)
§ Frost line
§ Money vs. labor
Foundation marked with stakes for round buildings or “batter boards” and string for rectilinear structures
If building with concrete forms are needed (usually wood)
§ Support with stakes
§ Straw bales can be used as forms in some cases
§ Can reuse wood forms if used carefully
Concrete foundations
§ Strong in compression, weak in tension
§ Very flexible, easy to build
§ Needs steel reinforcing bar
§ Types: continuous strip, “raft” with continuous slab
Pier and beam
§ Piers of wood or concrete. Beams span to support structure
§ Good on slopes
§ Good for raised floors
Pole foundations
§ Poles placed directly into ground
§ Good for sloped areas
§ Rigid structurally
§ Not very long lifespan. Can be longer if poles are treated
Rubble trench
§ Frank Lloyd Wright
§ Drainage trench of compacted stone and gravel capped with a concrete bond beam
§ Base needs to be below frostline
§ A perforated pipe is usually placed at bottom of trench (can also be formed of bricks)
§ Trench is sloped 1:8 to daylight or dry well
Stone
§ Rectangular stone best
§ Can be mortared or dry-stacked
§ Weak in tension. A concrete bond beam on top is good esp. in earthquake country
§ Lay stones “one over two”
“Alternative”/ experimental foundations
§ Gravel pad
§ Earthbags – fill with gravel or stabilized soil
§ Railroad ties with gravel fill
§ Tires filled with gravel/earth
Drainage
§ Determine drainage characteristics of soil
§ Don’t build in swampy areas
§ On slopes create swales/ berms upslope of building
§ Make sure all water from roof drains away from building. Slope soil around building away from building
§ “French drains” around outside of building useful for taking excess moisture away
§ Rubble trench combines drain and foundation
EARTHBAGS
§ Textile bags or tubes filled with soil sand or gravel to build structures. Can be stabilized or unstabilized
§ Somewhat similar to rammed earth
§ Bags of burlap/hessian or polypropylene (better) Burlap tends to rot and can be eaten by insects
§ Tubes are good because fewer joints, cheaper
History
§ Erosion control, embankments, bunkers
§
Gernot Minke –
§
Nader Khalili –
CalEarth,
Tools and Materials
§ Coffee cans
§ Shovels
§ Tamper (welded steel, wood post or concrete head on wood pole
§ Water hose
§ Wheelbarrow
§ Hoe
§ Knife/Scissors
§ Wire cutters
§ Level
§ Ladder
§ Tape measure
§ Gloves
§ Trowel
§ Old nails
§ Bags
§ Soil, sand or gravel
§ Compass (if building domes)
§ Barbed wire
§ Sticks
§ Sledge hammer
Advantages
§ Can build in almost any site, any condition
§ Can be used in areas with no clay or wood
§ Little or no cement is needed
§ Low material cost/ labor intensive
§ Bags cheap/ easily transported
How-to
§ Use rubble trench foundation
§ Initial bags are stabilized or filled with gravel
§ Earth is moistened slightly so it is easy to tamp
§ Fill bags in place. Can use a stand to keep bag open
§ Poke in bottom corners of bag after first couple of shovels of earth to make a more rectangular unit
§ Tubes are filled in different ways:
§ Gather tube around short piece of pipe, fill and let out gradually
§ Material placed in end of tube and moved to center by lifting
§ Different techniques used to keep layers from slipping
§ Barbed wire or thorny plants
§ “Dimples” formed by pounding bag with sledge hammer
§ Sticks laid between rows can act as an added mechanical key for plaster
§ Stagger joints in a running bond
§ Once bags are in place, tamp with feet and then with tamper until dense and compact. Sides can be tamped too.
§ Incorporate door and window rough framing while building
§ “Gringo blocks” similar to adobe construction can be used for attachment of door and window framing
§ Door and window frames can also be set first and bags set around them
§ Arched openings are usually only good for unglazed openings or fixed glass openings
§ Lintels of wood or concrete can be used above doors and windows
§ A bond beam can also be poured on top of bags for added strength
Arches
§ Utilizes formwork (usually of wood)
§ Pointed arch or catenary arch the strongest
§ Fill last three bags together in place to form wedge-shaped “keystone” bags
§ Buttressing of sides of arch is important
§ Place three layers of bags above arch before removing form
Domes
§ Only recommended for the driest climates
§ Use compass as guide. A compass is a rotating articulated guide
§ Only catenary or pointed domes are currently possible
§ Dome formed by corbelling layers of bags. Corbelling: flat rings gradually inching inwards
§ Domes need buttressing or tension ring at the bottom
§ A compression ring is used at the top
Straight walls
§ Need buttressing
§ Stagger joints for strongest wall
§ Make sure walls are plumb as you build
Plaster
§ Need to plaster as soon as possible to protect bags
§ First use “adhesion coat” of sand and boiled flour paste on bags
§ Can use mud plaster or lime/sand
§ Use lath especially with burlap bags as they can rot or be eaten by termites
Roof options
§ Wood frame
§ Brick dome on concrete bond beam
Problems with earthbags
§ Plaster sometimes doesn’t stick well to bags
§ Irregular surface can take up a lot of plaster (can be addressed by proper filling, laying and tamping)
§ Very “organic” shapes. Easier to be precise with tubes
AND OPTIONS FRAMING OPTIONS - FLOORS AND ROOFS CONCEPTUAL STRUCTURAL VALUES/RULES OF THUMB
Walls are the part of the house that connects the foundation and the roof.
Walls fulfill many purposes in a house, including:
§ Privacy
§ Keeping heat or cool in
§ Beauty
§ Keeping sound in or out
§ Keeping animals out
§ For hanging things on (pictures, cabinets, shelves etc.)
§ Creating a sense of refuge
§ Holding up the roof
The choice of wall system(s) depends on many different factors. These include:
§ Aesthetics (what you want the wall to look like)
§ Availability of materials
§ Climate (sun, humidity, rain, snow)
§ Ease of working with the wall material
§ Cultural factors (i.e. what is traditionally used in the area)
§ Site conditions (terrain, shade/sun, fire danger, etc.)
§ Privacy needs/ neighbors/ noise
§ Cost
§ Whether you are in the city or the country
The following list describes some of the wall systems used by natural builders.
Adobe (See Adobe section)
Cob (See Cob section)
Compressed Earth Blocks
§ Compressed earth blocks are similar to adobes
§ They use less water, are denser than adobes, and are much more uniform in shape.
§ Usually stabilized with cement
§ These blocks are created using a variety of machines.
§ Some use human labor and are relatively inexpensive.
§ Expensive fuel-powered machines can produce thousands of bricks in a day.
§ Because of their uniformity, compressed earth blocks need little or no mortar.
§ The regularity of the blocks speeds up the laying process
§ Results in straighter, more precise walls.
Earthbags (see Earthbag section)
Straw-Clay (Leichtlehm)
§ Leichtlehm (literally “light-clay”) is a German technique of tamping loose straw coated with clay slurry into forms.
§ The method is generally used to create infill walls in timber-frame structures.
§ Loose straw and clay slurry are tossed with pitchforks or mixed mechanically, then allowed to age for a day or so.
§ This allows the straw to absorb the extra moisture to create a stickier and more easily tamped mixture.
§ For more insulation less clay or lighter tamping can be used.
§ The straw-clay mixture is hand-tamped between forms in two-foot layers.
§ Once each layer is complete, the form is moved up and the next layer is tamped until the wall is complete.
§ The walls are allowed to dry before the plastering occurs.
§ Any shrinkage is taken up by stuffing more of the mixture into the cracks.
§ Straw-clay has been stuffed loose between rafters as insulation, the clay discouraging pests.
§ It has also been used as an insulating layer underneath earth floors.
§ Straw-clay tiles can be placed between roof rafters as insulation and as a plastering surface.
§ Straw-clay bricks can be used like lightweight adobes.
§ Wood chips or other materials can be mixed with the clay instead of straw
§ This is poured into forms instead of tamped.
§ These other materials can also be used to create lightweight bricks as well.
Rammed Earth
§ Rammed earth is an ancient earthbuilding technique
§ Used for parts of the Great Wall of China
§ Now updated with improved engineering, better forms, and innovative design.
§ Rammed earth has excellent thermal mass, strength, comfort and beauty.
§ Rammed earth can be built with simple forms and tools
§ Can be built in a variety of climates.
§ Walls do not need to be plastered and will last for hundreds, even thousands of years
§ Rammed earth is built on a foundation of stone or concrete.
§ A soil mixture of 20% clay with moisture content of 10% is rammed using mechanical or hand tampers in layers or “lifts” of 6-8 inches.
§ Different soil types can be layered to create decorative effects.
§ Electrical boxes, etc are placed in the form before the tamping begins
§ For efficient building, it is good to design around the form dimensions
§ A concrete bond beam that supports the roof tops the wall.
Straw Bale Construction (See Straw bale section)
Wattle and Daub
§ This technique involves weaving branches (wattle) as a support for mud plaster (daub)
§ It is perhaps the oldest of earthbuilding techniques
§ Still used for traditional architecture in many parts of the world.
§ Is commonly used to infill timber-frame structures
§ Strong, straight vertical members are attached to the sides of the frame, and at intervals in the space to be infilled.
§ Then flexible horizontal pieces are woven with the vertical members
§ Willow or another straight flexible wood is ideal for the horizontal members
§ The completed woven frame is an ideal recipient for plaster
§ This system can be used to create relatively thin walls compared to other earthbuilding systems
Wood
§ Wood is an ideal building material:
§ It is strong in compression and tension, easily worked and beautiful.
§ Important to protect wood against fire, moisture and insects
§ Few non-toxic preservatives available currently
§ Is commonly used to create post and beam structures
§ Other materials can be used as infill between the framework
§ House designs with small spans can minimize use of heavy timbers
§ Building systems which use unmilled poles can utilize smaller trees for identical strength with milled timbers from large trees
§ Some natural builders are finding uses for curved wood that is normally considered useless
§ Bentwood truss construction can be used to build strong beams using small diameter trees
§ Wood scraps and sawdust can be used for panels, hybrid products, etc., though many of these use toxic glues.
Cordwood
§ A traditional technique in Northeast America and other heavily forested ar eas
§ This technique uses small lengths of wood held together with a cement-based mortar.
§ To keep a cordwood house warm, an insulation layer of sawdust is used between the inner and outer mortar layers.
§ Cordwood can take advantage of plentiful small-diameter trees not useful for other building purposes.
§ It is relatively quick and easy to build.
§ Important that the wood is well seasoned so it doesn’t shrink.
§ A disadvantage is that differing rates of contraction can result in small gaps between the mortar and wood, leading to air or insect infiltration.
Hybrid Structures
§ Several building techniques can be combined to create a better building overall.
§ An example is to combine a thermal-mass technique such as cob or rammed earth on the south side of a house, with an insulating system such as straw bales or straw-clay on the north side, taking advantage of the best qualities of each.
§ Biggest issue is connecting the different materials
STRAW BALE CONSTRUCTION
Straw
§ By-product of cereal grain production. Can also use local grasses. Hay or material with seed heads is not recommended
§ Cheap if locally available
§ High insulation value (temperature and sound)
§ Low embodied energy
§ Renewable resource
History
§
First used in
Nebraska,
§ Stopped in 1940’s, a few isolated structures into the 1970’s
§ Rediscovered in the 1980’s. Now quite popular
Straw-bale building techniques
§ Load bearing
§ Straw-bales are structural
§ Can be less costly for simple structures
§ Good for low-cost temporary buildings
§ Can be mortared (“Quebec style” – now out of favor) or unmortared
§ Straw-bales are stacked like bricks
§ Best if openings are kept to a minimum
§ Need buttresses for unsupported walls
§ Need to allow for settling – though possible to “post-tension” bales
§ Best to design using bale dimension
§ Usually only good for smaller, one story buildings
§ This system utilizes many special “tricks of the trade”
§ Mortaring found to be unnecessary, possibly harmful
§ Infill (post and beam)
§ Frame structural system with bales as infill. Timber, steel or concrete frame
§ More flexibility of design
§ Roof can be constructed first – protect bales and provide shaded work area
§ Larger buildings are possible
§ Bales can be inside frame, outside or frame incorporated into the wall
§ Some details are more simple than in the load-bearing technique
§ Important to detail junctions between posts and bales because of different movement
§ Hybrid system
§ Combination of loadbearing and post and beam
Reinforcing (pinning)
§ Pinning used to connect bales to bales, bales to foundation, bales to door, window and structural frames
§ Pin materials: reinforcing bar, threaded rod, bamboo, saplings etc.
§ Interior pinning
§ Bales “impaled” on pins set in foundation
§ Bales pinned every 2-3 courses through middle of bale
§ Exterior pinning
§ Much easier than interior pinning
§ Pins are placed on exterior and tied in pairs through the bale
§ “Staples”
§ U-shaped pieces of reinforcing bar used at corners and other areas for extra reinforcement
Details
Making partial-sized bales
§ String threaded through bale using “bale needle”
§ Bale needle made from thin metal or wood dowel with slot or hole at end to take string
§ New strings are tied and old ones cut, can be saved and reused
§ Soft bales can be compressed with a homemade compactor and retied
Windows and doors
§ Rough frames of wood/plywood are placed during construction and anchored with pins, brace well!
§ Windows and doors must be at least one bale away from corners (loadbearing)
§ Leave space above frames to allow for compression
Straw in floors
§ Excellent insulation
§ Need to protect from damp
§ Can be used as part of a concrete slab or in timber floors
Problems with straw bale construction:
Fire
§ If bales are tightly compacted there is little danger, especially when plastered
§ Avoid loose straw in walls and fill gaps with cob or straw-clay
§ Be especially careful with straw in roofs or near chimney pipes
§ Be careful with welding, do not allow smoking on site, clean up loose straw
Moisture
§ Can be biggest problem
§ Make sure you have dry bales. Check with a moisture meter
§ If bales get wet, remove rotting straw and replace with cob or straw-clay
§ Use wide overhangs, “toe-ups” (upstand, like curb) on foundation, and dampproofing at details and openings
§ Slope water away from building
§ May make sense to drape first course of bales with waterproof sheet
§ Careful detailing/choice of plasters
§ Be careful of snow piling up against walls
Insects and rodents
§ Make sure there are no entrances through plaster
§ Usually not a problem once bales are plastered
§ Install a termite shield at the foundation if termites are a problem
COB CONSTRUCTION
History
§ “Cob” is the British term for building with lumps of stiff mud
§
Also known in
§
Cob popular in
§ By late 1800’s cob was considered “primitive” and much traditional knowledge was lost
§
Starting in the
late 1980’s a cob revival began in
Cob
§ Hand-formed lumps of clay, sand and straw. Can also include gravel and/or manure
§ Easy to learn – inexpensive to build
§ Can be used in cold, rainy climates with proper heat source and constant inhabitation during winter (cob acts as a heat sink, and if let to get too cold can be a problem to heat for intermittent use)
§ Can be done entirely by hand
§ Non-toxic and completely recyclable
§ Monolithic – stronger than adobe
§ More flexible in design than many earthbuilding techniques
Foundations for cob
§ Usually stone or concrete
§ Make them high, wider that the wall, and bumpy on top (good for connection of cob to foundation)
The cob mix
§ Sand – makes up most of the mix. Best is angular and well-graded (lots of different size particles)
§ Clay – usually 10-30% of the mix. Don’t use too much or cob will crack
§ Straw – good for tensile strength and insulation
§
Traditional mixes
in
§ Can vary proportions of mix for different functions
§ Best if you can “mix wet” so clay is well distributed and let dry a bit
§ Use a wetter mix in dry weather and dryer in wet weather
Mixing cob
§ Historically with animals of by four people turning over cob with forks
§ Adding clay:
§ Either sift clay if dry or soak it if it is wet. Makes it easier to mix
§ Make a clay soaking pit near site
§ Tarp method
§ Manual method usually easiest on back
§ Use a good (not too thin, but not too thick) tarp
§ Store tarps away from sun when not in use
§ A good impromptu tarp can be sewn together with hessian or polypropylene bags
§ Pour materials (except straw) alternatively on tarp (sand first, clay, sand, clay, etc.) and roll material to mix
§ Add water (15-20% of volume of dry ingredients)
§ “Dance” on clay/sand/water to mix
§ Turn mixture with tarp and dance again
§ Add straw while dancing
§ Turn mixture, etc.
§ Mix is done when it is a cohesive mass hard to sink your feet into
§ Pit method
§ Good for making large quantities of cob
§ Can create “wet” mixes which allows clay to mix in better
§ Don’t add materials too quickly or they will sink to the bottom, making it more difficult to mix
§ Mixing mechanically
§ Front end loaders, mortar mixers or rototillers can be used
§ Machines are not necessarily faster, often make inferior cob
§ Rototiller works excellently. Create a straight mixing trench or a hard mixing floor. Straw can get caught in blades
Building walls
§ “Pise” treading “flakes” of cob with feet
§ Best on lower parts of thick walls
§ Cob loaves
§ Forming balls of cob (”cobs”) which are pressed into the wall with fingers
§ Cob balls are easy to toss to a person working on the wall
§ “Gaab” cob
§ Masses of cob forked onto wall and pressed into wall with fingers
§ A “cobbers thumb” made out of a small piece of wood can help push material into wall
Structural integrity
§ Good bonding between layers necessary
§ Make sure straw binds between layers
§ Leave top of wall rough for good bonding later
§ Wet down top of wall if you haven’t been working for awhile
§ Don’t overwork the cob
§ Don’t hit or slap it into shape
§ If it bulges, often it is better to trim it later
§ Make sure wall is plumb (a level attached to a straight piece of wood can be used for this purpose)
Tapering
§ Making walls thinner as you build
§ Makes walls less heavy, use less materials
§ Use level taped to wedge-shaped board to determine proper angle of taper
§ Use dryer cob in wet weather, wetter in dryer weather
§ Poke holes in cob to allow for faster drying
§ Use dry materials as infill while building – can allow you to go higher faster
§ Use level or plumb-bob
§ Check work frequently – good to have a person designated as quality control
§ Avoid rounded tops of walls as you are building (“shouldering”)
§ Used to even out walls - makes it easier to plaster
§ Trim when “leather hard” – firm and solid, but still moist
§ Machete, axe, old handsaw, sharpened shovel, hoe, claw of hammer, all good tools for trimming
§ Very easy to make artistic details with cob
§ Corbelling
§ Technique for creating projecting elements
§ Special cobs with long linearly aligned straw added
§ Project these “corbel cobs” a little bit each layer
§ Arches can be formed the same way by gradually corbelling from each side of the arch
§ Niches
§ Form as you build or carve out later
§ Cob furniture
§ Example: heated benches with stove flue going through middle
§ Decorative elements
§ Bas-relief, etc.
§ If adding to a dry wall, texture surface first and add old nails, sticks etc. for reinforcement
§ Posts and wood frames
§ Wood frame first:
§ Key cob into wood using nails and/or vertical wood piece attached to post
§ Don’t bury posts into cob wall to avoid cracking
§ Make sure door frames are well-braced to avoid bowing of wood members from weight of cob
§ Cob first
§ Bury “deadman” (a block or log) or “gringo blocks” into wall for connecting posts/frames etc. later
§ Use “deadman” to attach rafters as well (horizontal piece with vertical piece or wire attached)
§ An alternative is to drill through cob wall with a masonry drill to provide chase for tie-downs
§ Deadman etc. can also be put in place for hanging cabinets, paintings, etc.
§ Build frame directly into wall. Brace well. Use lots of old nails to attach well to cob
§ Shrinkage is likely to occur at frames resulting in cracks. Scrape a “chase” of cob next to frames and fill when dry
§ Use strong lintels of wood, concrete or stone
§ Fixed pieces of glass or easy to “cob” into place. Tape edges first. Bury glass only ¼” into cob around edges to avoid glass breaking from cob shrinkage
§ Bottles can work as small windows
§ Can bury in wall.
§ Easiest to have entry of utilities below grade, so plan foundation accordingly
§ Don’t bury “T’s” inside wall
§ Make a careful drawing of utilities location for future reference
§ Very labor intensive (though mechanical mixing can save time)
§ Long wall-curing times
§ Cannot build in freezing weather
§ Earliest adobes (mud bricks) – 7000 BC
§ Adobe through history: Egyptians to Arabs to Spanish
§ Brought to “New World” by Spanish conquest.
§ A form of adobe already used in “New World.” First used in Caicama valley of Peru
§ They are formed of a complete saturation of a clay-sand mix with water
§ Traditional components: clay, silt, sand and straw
§ Stabilized adobes: add asphalt emulsion or cement
§ Code required for lower courses in US to avoid water damage to walls
§ Different shapes
§ Large for building quickly
§ Small – can be used by women and children
§ Flat – used to make domes and vaults in Middle East
§ Puddled or cone-shaped. Created without forms. Used by Native Americans and Africans
§ Half-sized adobes can also be formed to make building easier
§ Straw-clay blocks – very lightweight adobes. Good for situations with high clay soils and/or high insulation needs
§ Locally available, low-cost materials
§ Adaptable to a wide range of structures
§ Resistant to fire and insects
§ Good sound insulator
§ Easily stabilized if necessary
§ Hand-formed (puddled adobes)
§ Using forms of wood or metal (single or multiple adobes for each form)
§ Manually
§ With machines (bulldozers, etc.)
§ Mud is placed in form, then the form is immediately lifted off, or adobes are allowed to dry for a few hours, then form removed
§ Stone or concrete foundation
§ Usually not more than two stories
§ Adobes laid with joints staggered, mortared with adobe mud, or cement or lime mortar
§ Mortar joints 2-3 cm to take up unevenness of adobes
§ Wood “gringo blocks” used for doors and windows
§ Tops of walls with a wood or concrete “tie beam” especially in seismic areas
§ Horizontal reinforcing used every 4-6 courses
§ Appropriate in only the driest deserts
§ Must be built by experienced masons
§ Dangerous if built by the inexperienced
§ Can be built over any shaped room
§ Domes and leaning arch technique for vaults avoid use of formwork
§ “Squinch” technique used for non-circular domes
ROOFS / CEILINGS / INSULATION
§ Roofs are the protective cover for a building
§ They are composed of several layers:
§ Support structure
§ Structural surface
§ Waterproofing
§ Protective layer
§ Roofs are often the most complex part of the building
§ It is often a good idea to design the roof first, then determine how the walls need to be to support it
§ It is difficult to find a completely natural roof that is inexpensive and easy to build
§ Roofs must be sturdy and waterproof
§ Roofs must be designed and built carefully
§ A roof must be able to support dead loads (roof materials, etc.) and live loads (people), uplift (wind, etc.)
§ Steep roofs are appropriate in places with lots of snow
§ Steep roofs used elsewhere can absorb excessive amounts of heat
§ Shallow roofs are appropriate for dry climates
§ In addition the walls must be designed to support the type of roof used
§ Buttressing of the walls may be necessary to counteracting sideways thrusting of the roof
Roofs have to:
§ Protect against rain, snow, wind and excess light
§ Be solid, strong and waterproof
§ Prevent unwanted heat loss or gain
§ Because heat rises, most heat loss occurs through the roof
§ Therefore must be well-insulated: insulation, radiant barriers
§ Remain in place during hurricanes, earthquakes and high winds
§ Be well constructed and attached well to walls
§ Straps or metal hardware usually used
§ Be attached to a continuous strong bond beam on top of the wall
§ Resist snow or other temporary weight (like people)
§ Shed water away from the wall
§ Have overhangs in places that receive rain and snow
§ The worse the weather the bigger the overhangs
§ Overhangs must also block summer sun and let in winter sun
§ Have gutters in order to control splashing onto wall surfaces below
§ Whether you are planning to collect water of the roof.
§ Metal, tile are good for collecting water
§ Weight of roof material
§ Heavier materials demand a stronger roof and wall structure
§ Degree of flammability is a consideration for thatch or wood roofs in areas of high fire danger
§ Aesthetics, appropriateness for the region
Roof Types:
§ Not actually flat – they have a slight slope to drain water
§ Easier to build
§ Can easily leak – especially if they are built with parapets
§ Not recommended except for the driest climates
§ Sloped more steeply than a flat roof
§ Relatively easy to build and cover
§ Awkward side wall heights
§ Some find them aesthetically boring
§ Two surfaces which slope away from each other from a ridge
§ Can provide extra living space under the roof
§ Can easily expand house in the future with this type of roof
§ Rafters are attached to a ridge beam or board in the middle and held up by walls on the sides
§ In order to keep the rafters from pushing the walls apart they are connected by horizontal boards or cables
§ Buttresses could also be used to resist the sideways thrusting force
§ Trusses (manufactured structural components) can be used instead.
§ Because trusses are very strong they are often used to cover large spaces
§ Sloped on all four sides
§ Allows walls to be all the same height
§ Makes the bond beam easier
§ Rafters must be supported to avoid pushing walls apart
§ Special roofing systems
§ Only ones which rely on compression, not tension
§ Can use materials like stone, brick, adobe
§ Vaults:
§ Curved in a single direction
§ Usually used to cover a rectangular space
§ Leaning arches are used to build a vault without formwork
§ Domes:
§ Curved in two directions
§ Best used to cover a round or square room
§ Built using squinches, corbelling, or angled rings
§ Compass used as a guide
§ “Beehive” shape much stronger than hemisphere
§ Combinations of vaults and domes infinitely variable and very beautiful
§ Not to be built by the inexperienced
§ Usually only recommended for dry areas, especially when built of earth
§ These types of roofs are difficult to waterproof
§ These roofs do not shed water from walls - need special channels and gutters
§ Structural system to support roof:
§ Post and beam or bond beam on top of load bearing wall
§ Rafters
§ Trusses
§ Other (domes & vaults)
§ Next a layer which supports the waterproof layers
§ Wood planks
§ Latillas
§ An industrial board product like plywood is common. Natural alternatives are becoming available
§ Reflective foil is often applied under this for better thermal performance of the building
§ Waterproof layer
§ Usually some type of impermeable membrane (rubber is the only “natural” option here)
§ Vernacular building would use layers of bark. These have a tendency to leak, however.
§ Some roof systems do without this layer: thatch, tiles, metal
§ Protective layer of roofing materials itself
§ Bamboo is the largest of the grasses
§ It rows very quickly
§ It many places bamboo is a renewable resource
§ Currently being overharvested and facing the same ecosystem problems as deforestation
§ Strong in tension and compression - weak in bending
§ Good for poles, roof structures, straw-bale pins, reinforcement in concrete (if soaked and split)
§ Special joint details are necessary because it is difficult to nail or glue
§ Splits easily
§ Most common in tropics
§ Can be used as roof “tiles”
§ Negative image as “poor peoples” housing is beginning to change with new architecture
§ Uncommon in North America - still used in Europe and many “third world” countries
§ One of the only entirely natural roof systems available
§ Usually build on a wood or bamboo framework
§ Bundles of straw, reeds or palm leaves are tied to battens in overlapping layers
§ For longest lasting roofs the thatch is aligned so that only the very end of the straw/reeds/palm shows
§ Important to have sufficient roof pitch to shed water. The more rain, the steeper the pitch
§ Thatch roofs breathe, are highly insulating and beautiful
§ A well-thatched roof can last up to 60 years
§ A skilled thatcher is needed to build a roof which doesn’t leak
§ It is important to protect a thatched roof from fire and pests
§ In many countries thatching materials are increasingly rare and expensive
§ Most common material for roof structures
§ Sufficiently strong wood for structural members difficult to find as old growth forests have become overharvested
§ New composite beams becoming common – these can use smaller or lesser quality wood to create strong members
§ Steel often used to replace wood – much higher embodied energy, however
§ Wood is excellent because it easy to work and strong in tension
§ Some natural builders are finding uses for curved or otherwise unused timber in construction
§ Can be used as shakes (split from a log) or shingles (sawn from a log) as a roofing surface
§ Living material in soil or compost over a waterproof membrane
§ Usually built on a roof slope between 5-20 %
§ Very heavy - needs extra strong structure
§ Does not insulate well, especially when wet
§ Beautiful - helps building blend in landscape
§ Protects waterproof membrane
§ Waterproof membrane must be perfect as it is very difficult to find leaks afterwards
§ Be especially careful at skylights, chimneys and other protrusions through roof
§ Soil or compost for plants 10-50 cm thick is placed on top of waterproof membrane, then planted or pioneered by windborne seeds
§ For steeper slopes some sort of batten is used to keep soil from sliding off roof
§ Edge details are important for aesthetics and proper drainage of water off roof
§ Could be a fire hazard in dry climates
§ Not really “natural” but used by many natural builders as it is easily recyclable
§ Allows a very lightweight structure
§ Easy to apply by semi-skilled persons
§ Relatively inexpensive
§ Can be used for collecting drinking water
§ May need to paint to reduce annoying reflections
§ Stone - especially flat stone like slate - heavy
§ Ceramic tiles - heavy, but beautiful - collects water
§ Old tires cut up to make tiles
§ Compacted earth - traditional in desert climates
§ Concrete – easy - possible to surface other materials as a waterproof layer - high embodied energy
§ Asphalt impregnated products - common, but toxic, difficult to recycle
§ Usually the most problematic (natural building-wise) part of the roof assembly is the waterproofing layer
§ Most waterproof membranes depend on petroleum products
§ Some roof surfaces are the waterproof layer themselves (tiles, concrete, metal, thatch)
§ Traditional techniques (bark, earth) tend to leak
§ Big need for a “natural” waterproof membrane
§ Keeps excess heat or cold from entering / leaving a building
§ Most important in the roof
§ Insulation provides a thermal barrier by trapping small pockets of air that do not transmit heat well
§ Must protect from getting wet, animals
§ Wool - excellent, even if wet
§ Protect from moths
§ Whole sheepskins in plastic bags
§ Straw - fair insulator
§ Whole bales, or flakes of straw in roof
§ Must protect from fire
§ Fill gaps well so air cannot escape
§ Cellulose
§ Made from recycled news paper
§ Usually blown into a wall or roof cavity with a special machine
§ Perlite / vermiculite
§ Expanded minerals useful in moist or fire danger places
§ Overhead lining of a room
§ Holds up insulation
§ Provides attractive surface
§ Prevents warm air loss
Ceiling materials
§ Wood - attractive, sturdy
§
Can use recycled wood in ceilings (most recycled wood is not legal
usable for structural purposes in the
§ Latillas - small straight saplings
§ Beautiful, but time consuming
§ Straw-clay – can be placed as wood-supported tiles or “rolls” between roof rafters then plastered
§ Plaster - must be supported by a wood or metal lath
§ Board products
§ Several “green” board products are now available, though can be expensive
§ Homemade reed/clay/burlap boards are an option
§ Reed mats - simple and beautiful - some fire danger
§ Cloth - same advantages and disadvantages as mats
§ Materials spread onto a surface for protective and/or decorative reasons
§ Exterior and interior plasters have different requirements and are often made of different materials
§ They provide:
§ Protection from weather
§ Control of dust
§ Color and decoration
§ Texture
§ Durability to the wall surface
§ Most plasters are currently cement-based, but natural builders are returning to clay- and lime-based recipes
§ Can be rough or smooth
§ Wood or other materials can be covered with reed mats in order to be plastered
§ Tools
§ Good clean trowels
§ Swimming pool trowels are good for beginners
§ Putty knife
§ Plaster hawk
§ Clean brush and bucket for water
§ Tool for scratching first coat
§ Mortar or wood plaster boat (2m x 1m x 30cm)
§ Wheelbarrow
§ A mud board (70cm square wood on a stand)
§ Scaffold
§ People needed
§ One to sift materials and mix plaster
§ One to transfer materials to work site
§ One or more to do actual plastering
§ Exterior plastering best done in moderate weather
§ Avoid wind and rain
§ Do not plaster in freezing weather
§ Wait for bale settling or straw-clay shrinking to finish before plastering
§ Cover doors, windows, exposed wood with plastic to avoid staining
§ Lath around doors, windows, etc. may help cracking
§ Aesthetics
§ Degree of breathability
§ Maintenance
§ Desired hardness
§ Texture and “feel”
Hard plasters (cement-based)
§ Minimize maintenance
§ Easy to clean
§ Cold and hard to the touch
§ Poor acoustic properties
§ Difficult to nail and repair
Soft plasters (earth, gypsum and lime)
§ Pleasing to the touch
§ Easy to repair and nail
§ Good acoustics
§ Harder to clean
§ Need more frequent maintenance and replacement
§ Composed of cement and sand (plus lime and artificial fibers sometimes)
§ Not recommended for earth structures
§ Does not bond well – difference in expansion
§ Cracks let in moisture behind rigid stucco eroding soft earth behind
§ Often difficult to tell what is happening structurally until it is too late
§ Commonly used on straw-bale structures
§ High embodied energy
§ Easily available, skilled tradesmen common, standard “recipes”, resistant to water, high compression and shear strength
§ Brittle, difficult to repair, does not breathe
§ Usually uses lath and/or stucco netting tied/nailed to structure
§ This can be expensive and time-consuming to apply, especially for straw-bale structures
§ Has a long life
§ Bonds well to straw bales
§ Can be sprayed onto straw bales
§ Cement is irritating to the skin – need to use skin, eye and lung protection
§ Usually applied in three coats – scratch (thin scored coat to provide a good surface for next layer to adhere too, brown (thickest coat – provide final texture here) and color (very thin coat containing final color)
§ Mix dry ingredients first, then add water
§ Keep wall moist between coats
§ Some use polypropylene fibers to minimized cracking
§ Until recent introduction of cement plaster, lime/sand plaster most commonly used
§ Lime plasters are somewhat durable, porous plasters which evaporate moisture
§ Inhibits mold and mildew, repels some insects
§ Slightly lower embodied energy than cement, and its manufacture is less destructive
§ Possibility of local manufacture
§ Limestone or seashells are burned, which produces quicklime. This is then “slaked” in water to produce lime putty. Be sure to put lime into water, not other way around
§ Lime putty is the best to use for building
§ The longer lime putty ages, the better it becomes- more plastic
§ If you must use bagged hydrated lime, make sure it is fresh
§ Lime plasters are very slow to set
§ Must let each thin layer be exposed to air – with exposure to air the plaster changes back to limestone
§ Base coat often includes some sort of fiber- cow or goat hair
§ Can be “rough cast” (thrown onto a wall with a casting trowel)or troweled on
§ Scratched to provide good bond for next layer
§ Additives:
§ Linseed oil: durability and adhesion
§ Cactus juice: helps setting, adhesion, workability, water repellant
§ Tallow: plasticity and adhesion
§ Skim milk or whey: increase impermeability
§ Casein glue: strength and adhesion
§ Cement: small amounts to add strength
§ Pozzolans: speeds setting
§ Type “N” lime best used with earth
§ It has more calcium
§ Wash earth walls with “lime water” before applying plaster
§ First coat
§ 5 parts sand, 1 part lime putty
§ Second coat
§ 3 parts sand, 1 part lime putty
§ Third coat
§ 1 ½ parts sand, 1 part lime putty
§ Can put a final sealant of neutral soap and alum
§ Can be applied without wire reinforcement
§ More flexible than cement plasters
§ Lime can be mixed with earth to make a plaster (not with alkaline soils)
§ Can be used internally and externally
§ Do not use metal trowels - wood trowels are better
§ Must be “moist cured” with burlap or plastic to keep walls moist
§ Must be compacted with a trowel after application or will develop cracks
§ Only used on interiors because can deteriorate if exposed to water
§ Sets quickly - needs skilled plastering
§ Hard, white, easy to paint, smooth
§ Combination of sand, clay, and fine fibers
§ Has less than 30% clay
§ Straw or manure (fine fibers) an important ingredient
§ Lessens cracking
§ Apply plaster horizontally so that straw slows down water – keep rivulets from forming
§ Excellent for all types of walls
§ Needs ongoing maintenance -yearly ritual
§ Must be protected from water, ideally using overhangs
§ Beautiful and durable if kept dry
§ Suitable for exterior and interior surfaces
§ Best suited for dryer climates
§ Easiest plaster to apply
§ Can be applied by hand or with a trowel
§ Inexpensive, environmentally friendly, easy to repair, breathes
§ Additives to earth plasters
§ Lime water
§ Cactus mucilage – for workability and durability
§ Plant saps
§ Boiled flour - for surface hardness
§ Animal manure – to reduce cracking, workability, aesthetics
§ Ash - for workability
§ Borax + casein - resists moisture
§ Asphalt emulsion – waterproofness and durability
§ Gypsum
§ Eggs, blood – for hardness
§ Urine
§ Casein – for water protection/durability
§ Termite hills – for hardness
§ Glue – for durability
§ Oils – for water protection
§ Interior mud plasters can have a problem with “dusting”
§ Flour paste or glue can help
§ Preparations
§ Don’t need stucco netting
§ For straw-bales a thin layer of clay slurry sprayed into bales helps earth plasters adhere better
§ For earthbags apply an adhesion coat of flour paste/glue and sand
§ Dry mix materials first - then add water
§ Need to experiment with your soil to get a good mixture
§ Make fairly stiff mix
§ Application
§ Earth plaster is usually easiest to apply by hand - then troweled smooth
§ Start in the middle of the wall
§ Many plasters work from the top down
§ Apply plaster with an upward sweep
§ Fill low spots first and let dry
§ Let each layer dry completely before applying the next
§ Final plaster can be troweled rough or smooth
§ Can polish and compact final layer
§ Easy clean-up
§ Shingles
§ Boards
§ Gypsum board (interior)
§ Tiles
§ Living wall
§ Most paints are extremely toxic
§ Natural builders are rediscovering old recipes for non-toxic paints and finishes
§ Some non-toxic finishes are available commercially
§ Modern paints do not breathe well, traditional recipes more often do
§ Paints need: pigments, extenders, and binders
§ Can be used where wall surfaces do not need additional color
§ i.e. Earth plaster
§ Penetrating oil sealer - linseed oil
§ These can also be used on wooden surfaces
§ Oxides or pigments can also be added to final coat
§ High-tech sealants available – need to be reapplied
§ Historically most buildings were lime-washed on a regular basis
§ Adequately hard
§ Breathes, acts as a disinfectant
§ Will not peel
§ Cannot be applied over paints
§ Very stable on interior walls, but needs to be reapplied every year or two on exterior walls
§ Can be colored with use of pigments – these need to be lime-resistant
§ Caustic - handle carefully
§ Additives to improve durability
§ Linseed oil
§ Tallow
§ Skim milk (casein)
§ Salt
§ Cactus juice
§ Drying oil (i.e. linseed oil) and pigments
§ Casein (curds of sour milk) + kaolin clay + pigments
§ Kaolin clay + flour paste + pigments + fine sand
§ Paint on wall, then polish with plastic lid
§ Flour paste keeps paint from dusting
§ Can add mica, straw, borax (to prevent mold)
§ Smooth out final plaster coat with sponge before applying earth paint
§ After applying paint lightly, rub with sponge to erase brush marks
§ Usually the final part of the house
§ Many natural builders prefer “earth-coupled” (no vapor barrier) floors
§ Floors can be heated with radiant floor heating
§ Mass floors (brick, stone, concrete, earth) are an excellent source of thermal mass in passive solar design
§ Bricks on sand (with or without vapor barrier)
§ Concrete slab (can be covered with tiles)
§ Straw-bales covered with concrete
§ Can have a problem with excess moisture creating rotting
§ Soil-cement (can be made into pavers)
§ Stone and Sand
§ Earth
§ Poured or tamped
§ Beautiful, soft, warm
§ In dry climates earth floors can be built directly on subgrade
§ In cold/wet climates:
§ 12-18” subgrade
§ Porous base used 6-12” stone or sand
§ Moisture barriers can be used, but sacrifices breathability
§ Straw-clay can be used between stone and earth
§ Can add manure or blood to harden floor
§ Straw can be added to minimize cracking
§ Wheat paste, glue can be added for hardness
§ Can be poured wet, which cracks, or tamped, which usually doesn’t crack
§ Floor depth commonly 3-4”
§ Best done during dry part of year
§ Takes 10 days - six weeks to dry
§ Apply hardener (linseed oil thinned with turpentine) on dry floor in coats
§ Wax with beeswax (melted with linseed oil)
§ Save a bit of mud for later repair work
§ Wood
§ Necessary for second floors (natural)
§ Not good for thermal mass
UTILITIES (refer to other resources)
§ Heating systems
§ Electrical
§ PV
§ Wind
§ Etc.
§ Water
§ Gas
§ Use compact fluorescents instead of incandescents
§ Make efficiency saving on large appliances, especially refrigerators, ovens, washer and dryer
§ Solar water heating or on-demand water heaters
§ Composting or low-flush toilets
§ Low-flow showerheads
§ “Independent” home desirable
§ Energy systems
§ Photovoltaic
§ Wind
§ Microhydro
§ Conservation of energy is the most important
§ Save rain water for non-drinking purposes
§ Efficient water appliances
§ Gray water – recycle water to use on plants
§ Water efficient plantings, landscaping
LANDSCAPING
Food production
Aesthetic
Shade
Erosion control
§ Shovels
§ Tarps
§ Buckets (20 liters or more)
§ Drums (for holding water)
§ Level
§ Wheelbarrows
§ Compass
§ Machete
§ Picks etc.
§ Spray bottles
§ Plastering trowels
§ Screens for sifting soil: ¼”, 1/8”, window screen
§ Hoe
§ Old handsaw for trimming cob
§ Carpentry tools
§ Glass cutter and duct tape (for fixed glass windows)
§ String
§ Rags
§ Hatchets, axes, adzes
§ Chain saw
§ Paint brushes
§ Jars
§ Small plastic containers
§ Gloves
§ “Cobbers thumbs” (small pieces of wood comfortable to hold in the hand)
§ Bale needles
§ Hay knife
§ Plumb bob
§ Stakes
§ Water hose (if possible)
§ Straw bales
§ Loose straw
§ Cow manure
§ Clay soil
§ Sand or sandy soil
§ Water
§ Wood (natural and milled lumber)
§ Doors and windows
§ Glass
§ Old bottles (clear best)
§ Old nails
§ Hardware
§ Builders lime
§ Portland cement
§ Gypsum plaster
§ Linseed oil
§ Beeswax
§ Different colored clays
§ White kaolin clay
§ Plumbing and electrical supplies
§ Broken concrete
§ Polypropylene sacks
§ Waterproof roofing material
§ Bamboo or reeds
§ Small flexible sticks (willow is ideal)
§ Cheap white flour
§ Milk
§ Old bricks
COURSE SUMMARY
The ten-day intensive training course will explore the theory and practice of building using natural, non-toxic, and locally-available materials. It includes: how to find and select materials such as earth, stone, straw and wood; how to choose wall systems according to local climate and ecology; how to integrate various building techniques to create elegant, durable, and energy-efficient homes. Daily hands-on sessions teach the basics of building with cob, straw bales and rammed earth bags, adobe floors, earthen plasters, and natural roofs. The class will build a small prototype structure that will demonstrate foundations, walls, sculptural details, and other building techniques. Participants will also be led through the process of siting, designing and modeling a passive-solar cottage.
BACKGROUND
Most new development currently taking place world-wide is based on the industrial model. This model is destructive of cultural and natural resources, and has been aggressively pursued globally, with tragic ecological, social and economic consequences. The primary impact of this type of development has been on the built environment (housing and other structures).
However, a new approach
to design and construction is currently gaining momentum in North America,
Europe and
The field of natural building is a strong and vibrant movement, with an increasing number of practitioners, and a maturing sense of techniques and materials. However, knowledge of natural building materials and techniques has been slow to reach many parts of the world that could benefit from it.
Communities in the so-called developing world have the greatest need for housing solutions. These same communities, however, also have much to offer the rest of the world in the field of natural building. These communities often have rich traditions of building with earth, thatch and other locally-available and ecologically sound materials, which is little known outside their communities. This knowledge is in demand by the increasing numbers of builders, architects and homeowners who wish to decrease their reliance on financially and ecologically expensive building materials and techniques. Teaching techniques learned elsewhere in these communities is also an opportunity to visit and document existing examples of natural building for use by other communities.