by Athena and Bill Steen
illustrations by Andy Tannehill
CONTENTS Introduction Preparing the Base Waterproofing and Drainage Insulation The Sub Floor Finding a Soil Mix for the Finished Floor Installing the Finished Floor Method 1 Method! Method 3 Dividing with a Wooden Grid Stabilizing Earthen Floor Mixes Surface Hardeners and Sealents Floor Sealing Sequence Maintenance and Repairs Earthen Floors for Upper Stories Taylor Publishing [email protected]
www.dirtcheapbuilder.com 707-441-1632 PO Box 375 Cutten CA 95534 USA
Earthen Floors an introduction Earthen floors are one of the oldest flooring method used throughout the world in many climates and conditions. They have ranged from basic dirt, hardened and "sealed" from years of use, to elaborate clay mixtures poured in place, leveled, and highly polished. Because of their natural warmth, softness, and brcatliability, earthen floors make very comfortable living surfaces. Since local clay/soils can often be used and specialized labor is not required, earthen floors can be inexpensive More forgiving than brick, tile or concrete, they are easier to install, or repair. Well built floors can be quite durable even under high traffic. Once sealed, they can be swept, mopped or waxed the same as other floors. Earthen floors can be finished to look as one likes; smooth and shiny or more "earthy" - slightly matted and textured with flecks of straw. Wood can be placed into the floor to create a grid-like pattern, or the surface can be scored to look like tile. Different colored clays can be added to vary the color. Earthen floors can also be used as sub-flooring for coverings such as tile or carpet, and can be installed directly over existing concrete slabs. One of the most beautiful things about earthen floors, is that there is no one way of constructing one. Formulas for constructing earthen floors vary according to available materials, cultural traditions, climatic conditions and individual preferences. This booklet covens a few formulas that we have worked with succesfully. With some experimentation, testing and a basic understanding of the general principles, it will be possible to create your own earthen floor, that will be long-lasting, natural and beautiful.
P r e p a r i n g the Base To help prevent the floor from cracking or settling, the ground should be well compacted an free of all movement All organic and plant matter should be removed. If very expansive clay is present, it should be removed and replaced with another non-expansive soil or other substitute. The ground should also be dry before beginning construction of the floor
Waterproofing and drainage If the capillary rise of moisture is a problem, steps need to be taken to improve drainage and stop the upward movement of moisture. For many situations, a layer of 6 to 12 inches (15 to 25 cm), of either dry stone topped with gravel, gravel, or coarse sand may be adequate to improve drainage and stop moisture migration. Certain volcanic stones like pumice could also provide the additional benefit of insulation as well as protection from moisture. The uppermost portion can be comprised of finer gravel or coarse sand to prevent the upper layers of the floor from falling through. If more drastic measures are required, plastic or petroleum based membranes can be laid down, to prevent capillary rise, but at the cost of losing the b readability ofthe floor and contact with the earth itself Preferably, this membrane should be laid with care on top of a layer of sand to avoid any tears or punctures. If a non-synthetic, water-tight barrier is desired, a thin layer ( 1/4" to 3") of soil with a high clay content or bentonite can be used. It can be applied in a moist state in several layers, filling all cracks as each layer dries. Troweling each layer will help compact the clay mix and reduce the pore space. This will further aid in creating a water-tight seal. The top layer in particular needs to be wellcompacted. Bentonite sheets (1/4 thick, backed with cardboard), can also be purchased, although more costly. (See resources.) It might be possible that the application of a lime plaster which has been stabilized with a water-resistant material, like prickly pear cactus gel, could be effective as an anti-capillary barrier Whatever approach is used, it should be tested first to determine if it performs well. H
Depending on site conditions, a well constructed earthen floor may consist of several layers.
Insulation For insulation, 4 to 6 inches (10 to 15 cm) of straw/light-clay (see formula below), perlite/clay, pumice fines, or expanded day (clay that has been heated, expanded and filled with small air spaces) are some of the natural options that can be laid on top of the gravel or drainage layer. If desired, one can always resort to rigid foam insulation. Clay Slip A clay slip acts as the "glue" that binds together the straw or the perlite in straw/light-clay or perlite/clay mixes. A soil with very high clay content can be passed through a 1/8" screen to remove small stones and other debris. It is then mixed with enough water until it has a consistency of a latex paint. When a finger is dipped into the mixture, a coating should remain that obscures one's finger prints. Straw/light-clay Gay slip is slowly poured onto a small quantity of loose straw (2-3 flakes) at a time, then mixed either by hand or with pitchforks, until each straw is coated with clay slip, similar to tossing a giant salad, when the straw sticks together in a bundle when tightly squeezed, the mix is ready. To keep the mixture from drying out while more is being made, it can be stored under a tarp. If allowed to sit for a couple of days, the mixture matures and improves. The straw/light-clay needs to be tamped such that poorly integrated layers are not created. The butt end of a 2x4 works to tamp and work the mix together. Upon completion, the straw/light-clay needs to be solid and not spongy.
*A solid and compact layer of straw/light clay requires practice and can be somewhat labor intensive.
Mixing Straw/Light Clay
Perlite (or vermiculite)/light clay Perlite is mixed with a clay slip, either by hand or with a concrete or mortar mixer. Enough slip needs to be added so that the perlite binds together and that the mix has sufficient density. Like most facets of the earthen floor making process, experimentation will be needed to yield the proper proportions. Pumice fines (or other lightweight volcanic stone) can most likely be laid dry and tamped for good compaction.
The Sub-Floor The finished earthen floor, needs to rest on a compact, level surface. If an insulating and/or drainage layer has not been used, the sub-floor can be nothing more than the well-compacted ground. Otherwise, 2 to 3 inches of compacted silty/sandy soil (not pure sand) can be applied over the insulating or drainage layer to insure a solid base. This soil needs to have enough day that it holds together when dry. Slightly moistening the soil will help the initial compaction. The sub-floor can serve as a good working surface during the final construction stages of the building. Foot traffic will help compact the bottom layers.
Radiant floor tubing can be installed into this sub-floor layer.
Finding a Soil Mix for the Finished Floor Layer Determining a good soil mixture, a combination of clay, sand and fiber (chopped straw), is the most critical step of the finished floor layer. The mixture needs to have sufficient clay to bind all the ingredients together with good strength. Conducting a series of tests using varying proportions of these ingredients, is a crucial step. The strongest earthen floor is one that doesn't crack. Cracks, even when filled or grouted remain the weakest and most vulnerable part of the floor to damage. Creating test samples to see how they dry is crucial.
Analyzing soil for clay content To determine whether or not soils contain enough clay to be used for a floor, several simple tests can be done. One is to form the moistened soil into a round egg-sized ball using just enough water to bind it together without it sticking to the hands. Let it drop. If it breaks easily there is most likely not enough clay content. If it resists breaking and has a sticky adhesive quality, the clay content is probably sufficient. The same ball can also be cut in half with a knife. A shiny surface on the soil reveals clay while a dull surface indicates silt Another indicator is that clayey soils resist penetration of a knife while silty/sandy soils show little resistance. Handling and feeling different soils and noting the differences between them will begin to reveal a lot about them. With a little experience you will have a natural sense about what generally needs to be added to correctly adjust the soil.
Mixing Test S a m p l e s for Finished F l o o r To find a mix for the finished floor, the soil being used needs to be tested first alone and then sit h varying quantities of sand and/or straw.
Both the soil as well as the sand should be sifted through 3/8 inch hardware doth to remove any larger particles, debris and stones. Mix enough material to create test samples that are approximately 1/2 to 1" thick and 12* square
Clay soil by itself Mix with water without sand or straw
Clay soil and sand Dry mix different proportions of soil and sand Add increments of sand: 1/2 part sand to 1 part clay/soil 1 part sand to 1 part day/soil, etc. Continue up to 3 parts for starters. Add enough water to thoroughly blend alt the ingredients. The mix should be kept as dry as possible and yet remain workable. These samples should dry in the same place where the finished floor will be installed. Make sure the samples are marked with their appropriate percentage of clay and sand. When dry, choose the sample that has no cracking and has sufficient strength. Too much sand will produce a weak floor. If by chance, none of the samples are free of cracks, the soil being used may be unsatisfactory because of the expansive nature of the clay.
If the crack-free sample lacks adequate strength, it is then necessary to work backwards. Select several of the samples that seem to have good strength and start over by remixing them but this time with straw. Begin by adding 5% and continue in increments of 5% up to 25%. When dry, observe to see if there are any samples that are crack-free and that have good strength and density. Too much strew may yield samples that lack sufficient density for a good floor The straw used should be finely chopped (straw passed through a 1/4" or 1/8* screen).
Clay soil with straw Another option is to mix the clay soil with only straw and no sand. In this case the concentration of straw will need to be higher than if sand were added. As above, add straw in increasing increments, 5% at a time This approach has value when sand is difficult to come by or is an added expense when money is scarce. With such a high quantity of straw added, there may be more difficulty achieving enough compaction and strength.
Sanely soils There are some soils that are too sandy or silty by nature and lack sufficient clay to produce a good floor mix. There are basically two major options in this case. Either additional clay can be added to bring it up to a suitable level or a small amount of portland cement (6 to 10%) can be added. Cement is probably the most commonly available stabilizer for sandy soils. Straw can also be added for effect, if wanted, to any test sample that produced good results without it. Once a mix has been selected, a larger test sample (a square meter) can be completed for final confirmation.
We have included three different methods for installing earthenfloors, lire steps which have been covered prior to this point are the same for each method unless stated otherwise. Method 1 is a troweledfloor that is both durable and beautiful, but is the most labor intensive of the three methods. It is our choice for areas that receive the most traffic and where an attractive floor is desired Method 2 is a tamped floor that is of lower quality than method 1, but isfaster to install. It would be a good choicefor areas with less traffic or where the finished look is not as important It wotild also be a good choice when using an earthen floor as a base for tile, carpeting, etc. Method 3 is the easiest andfastest of the three methods, but the most experimental and the one for which we have the least amount of data. It is simply installed dry and moistened in place using psyllium seed as a stabilizer. We have created some incredible samples using this method, but consistent results will require more work and experimentation.
Method 1 This version produces the most finely finished and durable earthen floor that we have seen. If the base for the floor has been properly prepared, the thickness of the finished floor can be thin, anywhere from 1 to 2 inches. Historically, earthen floors have often been treated like concrete pours and have been installed at a thickness of 4 inches or more, but this excessive thickness can make the floor much more susceptible to cracking and substantially increase the drying time.
Typically, we have had good results with a 1" finished floor layer, applied in two seperate 1/2" thick applications. It is conceivable that it could also be done in one layer, although there would be more shrinkage and cracking problems. Three layers might be necessary, if problems have developed as the floor is being installed.
Getting ready to begin. Before beginning, the height of the various floor layers need to be marked on the walls of the room. For example, if two 1/2" layers are being used, a mark 1/2" above the top of the sub-floor, along with another at 1", need to be made. These marks can then be connected by drawing level lines between them, or snapping a chalk line. A water-tube level in combination with a Standard carpenter's level are usually adequate for most rooms, however a transit could be helpful for larger rooms. Prepare your tested floor mixture, measuring the ingredients carefully, so that each batch is consistent. Thoroughly dry mix. It is a good idea to save and store some of this dry-mix for future repairs. Just enough water should be added to make the mix workable. The drier the mix, the less the floor will shrink and crack. Straw added to the first layer will help control shrinkage. The base needs to be thoroughly clean (a vacuum works well for this), and dampened before applying the floor mixture.
Applying the floor mixture is most easily done with a trowel Swimming pool trowels have rounded corners and are easier to use with earthen materials. Standard square cornered trowels have a tendency to leave marks and are harder to control A 3" to 4" putty knife can help when it is necessary to work corners. Longer, concrete floor trowels, also work well and help to level larger areas of the floor.
The base needs to be kept damp, especially the area where the mix is being applied. This keeps the base from wicking water too quickly out of the floor mixture, and thus producing cracks. It is best to do an entire room at one time. However, if it is a large room, or time does not permit it is possible to stop and resume
later, as long as the tapered edge of the last section is well moistened before continuing
Where the earthen floor meets a wall, a door sill, or any different type of material, such as brick, concrete or wood, a 1/2" strip of drier mix, should be used to minimize shrinkage. Some dry mix can simply be added to what has been already mixed for the rest of the floor
Keeping the floor level as you go. It is usually easier to apply the floor mixture in 2 foot wide strips across the room. When finishing each strip, it is extremely important that the edges of each of these sections be tapered or beveled and then scored or scratched. In this way the following section will overlap and integrate well with the previous one. Failure to taper each section at the edge will typically produce cracks wherever sections meet.
There are a variety of techniques that can be used to keep the floor level while each application is being made. To check the level and to remove any excess material or unevenness a 3 foot level is handy. It can be attached or taped to a length of milled lumber of the same or slightly longer length, to drag across sections that have been installed.
As guides or reference points while troweling the earthen mixture! sections of re-bar or pieces of wood (the same dimension as the depth of the application) laid at periodic intervals across the base layer. For example, if each layer is one half inch thick, a piece of #4 re-bar can be used as a guide to regulate depth. As each section of floor is completed, the re-bar or wooden guides can be removed and repositioned for the next section. Make sure to carefully fill the gaps left after removing the guides.
When a room is large, it can be difficult to maintain a level surface when installing the floor. One remedy is to use pre-laid, 3 4" strips of floor mix at approximately 6 intervals, to create reference points for the correct height of the floor. Once in place they can also be used to lay a board or level across and adjust the height of the floor. 1
The first layer of earthen mix can be left slightly rough so that the second layer will better adhere to it. There is a point when the floor will be dry enough to walk across -yet still damp enough to be workable. At this time, any cracks or shrinkage lines that have occurred, can be worked with a trowel. This first layer can be left fairly rough for the next layer to adhere to. To help spread the concentrated loads of feet and knees, so that no marks or depressions will be left on the floor surface, two pieces of plywood or some other flat, rigid material can be alternately leap-froged across to create a path of movement.
T h e second layer Optimally; the second earthen floor layer should be applied while the first layer is still damp, yet leather-hard. If the first layer dries out before applying the second layer, be sure to dampen it well before starting, and while working. If for any reason, the first layer showed any cracking, adjust the soil mixture and retest before applying the second layer The second layer of the earthen floor is applied in exactly the same manner as the first. Once the floor has hardened, but is still damp, it can be troweled, using a little water, to give a smooth, fine polish. A spray bottle works well to apply the water. Wiping the floor lightly with a wet sponge and troweling it will bring out the flecks of straw. Depending on the weather, the entire floor could dry in as short of time as a few days in drier climates or as much as several weeks in damper conditions. A fan could help speed up the drying process. AD traffic should be kept off the floor during this time.
Adding water The first layer can be applied dry and then moistened slightly with a mister on a hose or a watering can. The soil mixture should be wet enough that the clay can bind the ingredients together, but not so wet that it can't be walked upon without disturbing it. The mixture can also be lightly moistened before applying. Doing so helps ensure that the moisture is evenly distributed throughout the mix, but it is more laborious. Another option, which will help further stabilize the soil, is to add boiled linseed oil to the water at a rate of 4 liters of boiled linseed oil, diluted with 2 liters of water for every 100 liters of soil (by volume).
Method2 This method produces a floor that is not as durable as Method /, but is easier to install.
The technique It is possible to construct an earthen floor by tamping or ramming. It can also be done in multiple layers, but at greater thickness because it is done with a dry or slightly moistened mixture rather than one which is wet enough to trowel. The Initial layers of this floor need not be as finely screened as for Method 1. Soil passed through a 1/2 inch screen is more than satisfactory. Select a clay/sand mix as described earlier in the text. Prepared road base has also been used with good results. Each layer can be somewhere between 1.5 to 2 inches in depth with the total depth of the floor at 4 to 6 inches or more if conditions require it.
The mixture can then be roughly leveled and then compacted with a plate compactor. Hand tamping is clearly the least expensive, but more laborious. Simple tampers can be made from plywood with a handle or metal plates welded to a piece of pipe. Mechanical plate compactors are commonly available through tool rental outlets. When using one, it is necessary to handtamp the edges of the room where the floor meets the walls.
Additional layers When this first layer is completed, it can be followed with other layer or layers. If the finished look of the floor is not so critical, this can be the final layer. More care can be taken to level the surface. Dragging a board across the surface to screed it as done with concrete is a good method Tamping will produce edges, but these can be smoothed or softened with a trowel and retamped to create a reasonably level surface If this is the final layer, it should be applied slightly higher than the intended height of the floor as tamping will compact the floor mixture approximately 20 to 30%.
Final layer If the surface of the final layer is not smooth enough, it can be topped with a very thin troweled-on application of the same soil mixture, screened with 1/8* hardware cloth. It is applied in the same way that one would apply a finish plaster to a wall. Care should be taken to make sure that the previous layer is well moistened to ensure a good bond between the two. A hybrid version of Method 1 and 2 can also be used for the final layer. A1/2 inch layer of a clay/soil mix, as in Method 1, can be troweled on top of the tamped layers.
Method 3 This is the fastest method of the three, but less finished with more texture than methods 1 and 2. It is also suitable for outdoor surfaces in dry climates.
Application This mix is spread dry over the base layer that has been soaked with water. It is then leveled and compacted with a roller, as is typically used for landscaping. The soil and psyllium mix is then saturated with water by using a spray nozzle that has a mist option. Applying the water in a mist does not disturb the prepared surface of the floor. It is essential to moisten the soil mixture so that the full depth of the material receives water. After the surface water disappears, the surface can be further compacted with a roller. The top layer can be troweled lightly to help seal the surface of the floor and to produce a smooth surface. Too much pressure will tend to float the psyllium to the top and weaken the bottom layers. The surface can be misted or moistened slightly to facilitate the process. It is possible to apply the psyllium in a wet mix with a trowel, like in method 1, but it can be difficult to control the consistency of the soil psyllium mix. Which has a tendency to continue absorbing moisture and consequently continues becoming drier and changing in consistency. However, some experimentation may yield good results. Small samples that we have created using this method have yielded good results.
Volume of soil needed for the finished floor layer
Soil Mixture This method uses psyllium seed as a stabilizer in combination with a sandy soil mix or another material that has a fair amount of aggregate. Psyllium acts like clay or cement, it coats small pieces of aggregate and triads them together, ft is often used with crushed granite for outdoor walkways. Ground psyllium seed (see resource section) is dry mixed at the rate of 1 lb. per 10 square feet to create a 2 inch thick floor. For a 3 inch thick floor, 1 lb. per 7 square feet is needed. A mortar mixer or concrete mixer is good for larger quantities.
At adepth of 1 inch, approximately 1 ton of soil mixture will be needed for every 200 square feet; for 2 inches, 1 ton per 200 square feet is needed; for 3 inches, 1 ton per 65 square feet.
Earthen floors can be divided with grids of wood, brick, concrete QT other m a t e r i a l s If wishing to do this, it is important to remember that earthen doors are strongest to a monolithic form without any divisions Their weakest point is at the edges and when divided by other materials, the number of edges increases considerably. Dividing the floor into sections does make it easier to level Smaller tile-sized sections can also be made and then grouted with a different colored clay
M i x 1 cup of white wheat flour with I pint of water and add it to 2 cups of boiling water. Then cook at low heat until it becomes slightly translucent taking care that the mixture does not stick and burn Dilute this with 2 quarts of cold water and use it as the water to mix the soil ingredients. Another option is using casein powder which produces a natural glue. It is prepared by soaking 25 grams of casein powder and 8 grams of borax in enough water to form a putty. The putty can then be diluted with water to a consistency suitable for mixing the soil ingredients Auro (see resources) makes a powdered casein glue that could also be used Synthetic polymer based glues like Elmers or Concrete Bonder can be used at a ratio of 16 ounces to 22 shovels of mix.
Surface Hardeners and Sealents
Stabilizing Earthen Floor Mixes Most soil mixes will make a good floor without additional stabilization. They can be added if additional hardness is required or if the soil mix doesn't produce enough binding and strength. Choice of stabilizers can vary depending upon available resources. An easy and inexpensive stabilizer that was sometimes used throughout the southwestern United States was wheat flour paste Wheat flour paste can be made from commonly available white flour mixed in the following manner
To be effective, a good sealant needs to penetrate deeply into the earthen floor rather than form a skin or shell on the surface of the floor, as do acrylic sealants. The problem with skins, is that they create a thin, hard cap on top of a relatively soft material (the earthen floor). This cap or skin is then susceptible to damage and when it is broken, produces "pot holes" in the floor. Traditionally, the most successful sealents have included oils, animal urine and bloods. Penetrating oils, which oxidize and become fixed, are often the best choice for earthen floors, as they not only seal, but harden the floor as well. Unseed oil is probably the most cost effective and widely available of these oils. However, other options include hemp oil, castor oil and possibly, cottonseed, coconut, and fish oils. Boiled oils are preferred, because they require much less time to dry. Another option which we have not tried, but that could be superior to any of the above is stand oil. Stand oil is usually linseed or tung oil which has been exposed to oxygen in order to oxidize it In former times, oils were left to stand exposed to the oxygen in the air tQ produce the same effect and dais the name, stand oil, however stand oils can now be produced by injecting oxygen into the oil
There are a number of varnish combinations which are manufactured in Europe that are composed of varying combinations of linseed oil, tung oils, solvents, dryers and other substances that could also be effective, particularly for the final coat. A source for these products is Sinan (see resources) which is a representative for a European company named Auro which manufactures a complete line of natural paints, oils, solvents and related products. Their linseed oil is organically grown and not diluted with any type of petroleum solvent A solvent for thinning the oil will also be necessary. There a number of options which include everything from common mineral spirits and turpentine to more expensive environmentally friendly thinners diluted with citrus oils, ordorless turpentine and pure citrus oils. Unfortunately almost all of the natural oils and solvents are considerably more expensive. Oils penetrate deeper and more effectively when they are heated, and will also be more readily absorbed, if the surface of the floor and the room are warm. // is extremely important to remember that both oils and solvents are very volatile and flammable and need to be treated with great caution when heating. Any brushes and equipment used during the application are also subject to spontaneous combustion after they have been used and should be carefully stored in closed containers
Generally, it is better to apply the oil in a stronger concentration
in the initial coats, gradually reducing the percentage of oil to solvent in the following coats. The earthen floor is less porous with each subsequent coat of sealant, and will accept full strength oil more readily at the beginning. Our best results have come from applying full strength oil for the first coat, gradually diluting it in several subsequent coats.
Floor Sealing Sequence The floor should be completely dry before sealing. The oil/ solvents to be most effective should be heated, but only with the utmost caution. They should be warmed, but not taken to the point where they began to smoke. Each coat should be applied only to the point that the floor can accept the quantity being applied and no more. If it starts to puddle, the oil/solvent combination may form a cap on the surface of the floor. A large brush can be used to apply the oil. Remove excess oil. Coat 1 - Apply full strength oil Coat 2- Dilute the oil with 25% solvent Coat 3- Dilute with 50% solvent Coat 4- Dilute with 75% solvent Subsequent coats should be applied as soon as the previous one is fully absorbed and no longer tacky to the touch. With 4 coats, the floor should be sufficiently sealed, yet if more sheen is wanted, additional applications of "Coat 4" can be added. Some of the above mentioned varnish preparations might be effective as a final coat. Since no specific testing has been conducted on earthen floors, small samples should be experimented with before attempting an entire floor. Watch that an impermeable cap or skin on the floor is not created. Besides stand oils and linseed oil varnish, Auro manufactures a product called Natural Resin Floor Sealer that is a combination of different stand oils, solvents, and dryers that could be very effective. They also have another product called Clear Amber Varnish which is also a combination of stand oils and solvents, but also includes colophon amber which gives a harder finish.
Periodic Applications of Coat 4" can be used at maitenance coats The frequency of this application will depend upon the amount of wear the floor receives For an average floor, somewhere between 6 months to a year is sufficient. Although, if a high sheen is not important, the Boor can go years without the addition of any further coats or maintenance The application of a hard wax can also be used Recipe for hard wax: 250 kg's of camuba wax, 250 kg's of beeswax and 5 kg's of turpentine or other solvent, all dissolved together in a
double boiler Auro produces two different floor wax products that could be used for floor maintenance Beeswax floor care is designed for regular floor care and produces a water-repellent coating while Floor and Furniture Plant Wax contains carnauba wax and gives a harder finish.
Repairs If the floor needs repair, open up the crack or hole, splaying the edges, so that the hole or crack is smaller at the top than at the bottom. If the crack or hole is small, it can help to pass the mix through window screen to remove any large particles and debris. Thoroughly moisten the floor when applying the new mix. Seal when dry.
There is a variety of reinforced and/or stabilized load-bearing earth and earth/straw in-fills that can be used between floor joists to provide a satisfactory base for an upper-level earthen floor. It is important to establish a solid enough base that doesn't move (so uncharactenstiocharacteristic of many wooden floors). Another consideration is that an upper-story earthen floor will most likely be quite heavy and the calculated loads must be within the limits of the structure Reducing the span between floor joists can help distribute loads along the walls, but also improve the performance of the in-fill material Light clay/straw is possibly the best in-fill, in that it is lighter than solid earth, a good insulator and has good tensile, shear and bending strength. The light day/straw mix can either be packed directly between the floor joists or beams, or can be made into prefabricated panels or blocks, and positioned once dry. Some type of horizontal reinforcing element, such as; lx2's, 1/2" re-bar, 1" bamboo, willow branches, or some other type of branch, spaced every few inches, needs to be integrated into the light clay/straw in order to make it load-bearing in a flat position. These reinforcing elements need to be strong enough to carry the loads imposed on them from above as well as the weight of the infill material itself. Once the infill portion has been completed and is thoroughly dry, a 1 inch thick (two 1/2 inch layers) section of earthen floor can be installed, as described earlier in the text If the floor joists are to be exposed, the infill material should stop 1 inch below their top, and if they are to be covered, the infill material should cover them with at least 2 inches of material. Burlap, coated with a clay slip can be placed on top of the straw/light day if further protection from cracking is desired. Any of the light day/straw infills can then be plastered underneath, on the ceiling side.
Obviously the construction of an upper-story floor in terms of the actual construction and the calculation of loads, etc. is more complicated them can be dealt with in a small booklet like this, but we have included short descriptions of the basic techniques to give the reader some idea of how these infill sections are constructed. The relationship between the load of the light clay/straw to the joists and walls as well as the technique for constructing the in fill, needs to be thoroughly understood before attempting this type of construction.
Prefabricated blocks of straw/light-clay T-shaped straw/light-clay blocks can be prefabricated to rest between the rafters or floor joists. Two reinforcing rods are worked into the middle of the block when packing the wet mix into the form. The blocks can be removed immediately from the form and set aside to dry. A little clay slip can be used between the blocks as mortar, when the dried blocks are laid in place. The blocks can be shaped to produce either a flat or vaulted ceiling.
Light clay/straw infill A mixture of light clay/straw can be tamped directly into place, using a slip-form attached to the bottom of the joists or rafters thus producing a flat surface when the form work is removed The reinforcement rods, placed every 2-4 inches, rest on the ledgers which are attached to the lower sides of the joists.
Light clay/straw ceiling rolls
These infill sections can also be curved by using a form work of flexible branches such as willow which are bent to the desired arc and placed 1 or 2 inches apart The light clay/straw is then packed on top of them.
Another version of creating a flat infill section, is to use reels made up of a fibrous material, like straw or grass, coated with clay slip and then wrapped around reinforcing rods. These reels are slid between the joists, compactly against each other while still wet. As with the other infill methods, the bottom of the rolls can then be plastered.
Yavapai Sports Surfaces P.O. BOx 17150 Ft. McDowell, AZ 8S264 (602)837-8038 $ 1-80O-9-2724 Psyllium seed r
Sinan Company P.O. Box 857 Davis, CA 95617-3104 (916)75-3104 Auro products-natural paints, oils solvents, waxes, etc The Pilot Chemical Co. 1030 Jackson Ave. Long Island, NY 11101 (718)729-8282 Casein powder Frank Andreson Duseldorf, Germany summer address: P.O. Box 249 Brownfield ME 04010
We have worked with Frank Andreson of Germany who Is skilled with many years* experience In building with light
Wc ait a small non-profit organization dedicated to connecting people, different cultures and nature. Our work explores living, building and food production practices that can be simultaneously beautiful and sustainable The Canelo Project is defined by the place we call home - a 41 acre secluded homestead tucked into the higher elevation oak woodlands of southeastern Arizona. Shaped and nurtured over the last eight years, the site provides a comfortable and peaceful context for learning, applied research, and cultural exchanges. Our current projects include: • Workshops and Tours Ongoing programs focusing on natural building, straw bale construction and the living arts. • Straw-Earthen Housing in Mexico Innovative low-cost housing using local and natural resources. • Enjarradora Program Training women and children In the traditional livelihood of working and building with earth. • International Exchange Bringing together people from around the world, to share their specialized skills and cultural knowledge. We invite you to join us and participate in any of our ongoing activities. We welcome your interest and support. If you would like more information about the Canelo Project, workshops, and other mail order products, or for more copies of "Earthen Floors*' ($8.50 + $1.50 shipping) Call or write to: THE CANELO PROJECT Athena and BIO Steen HC1 Box 324 Elgin, AZ 85611 (520) 455-5548 fex(520) 455-9360
all donations are tax-exempt
When I was a boy, my father was the main one to look after the church. Once when we had been up to southern Colorado to visit part of our familyfor a couple of weeks, it had been raining here almost every day we were gone, heavy rains. The day after we got back, my father took me with him to go see how Aings were with the church. We could see as soon as we walked up to the church how heavy the rains had been. The adobe plaster was washed away here and there, and the winds had blown a cottonwood limb onto the roof When we went to open the doors, the wood was so swollen by the water that we could barely open them. When we got them open and saw inside, we just stood there awhile not saying anything* There, growing out of the adobe floor, was a young stand of wheat I remember trying to convince my father to leave the wheat alone-it seemed right to me that it should be there-but he Just smiled and said, "Ml hijo, you know we can H worship the wheat lna couple of days, everything was back to the way it was, but I never forgot that day. n
Elder from northern New Mexico village.
Persistence of Memory \ New Mexico's Churches Museum of New Mexico Press