Category Archives: Habitat-Materials

Earthen floors

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By Sukita Reay Crimmel, James Thomson, and Frank Meyer on The Art of Natural Building

Most traditional earthen floors are just the raw earth, tamped down with human feet and moistened frequently with water to keep the dust down. Sometimes sealers are used to stabilize the earth more permanently.
Earthen floors are remarkably versatile, but may not be suitable for every application. It’s useful to understand a few of their key characteristics to determine where they should and should not be installed.

Weight:  Earthen floors are heavy; they require a stable and strong subfloor. Most typically they are built “on grade” (i.e., directly on the ground), over a strong base pad made of concrete or compacted gravel (road base). They can also be built on raised wooden subfloors, even on second or third levels if the structure is strong enough to support the additional weight; consult with an engineer if in doubt. An advantage of heavy floors is that they are a good source of thermal mass, which helps moderate indoor temperature fluctuations.

Hardness: The surface of an earthen floor can look and even feel like concrete, but it does not have the same compressive strength. Earthen floors can be dented by point loads or scratched by heavy objects. Their hardness can be compared to that of a wood floor. Experience has shown that because they are softer, earthen floors are more comfortable to stand and walk on than concrete floors.

Water resistance: Sealing with the right kind of oil gives earthen floors a durable, waterproof finish. You can spill water on them and even mop them without any problem. But below the sealed surface, the floor is still unstabilized earth. Prolonged exposure to lots of water could have negative consequences, as the water seeps through cracks and pores into the layers beneath. Earthen floors have been successfully installed in bathrooms, but shouldn’t be used in showers or in basements that flood.

Thickness: Earthen floors are usually ¾–2 in. (2–5 cm) thick. It’s important to consider this added thickness when planning for transitions to adjacent rooms or entryways, or in rooms with already-low headroom.

 Installation time: Earthen floors are not a quick flooring solution. Drying and curing are the most time-consuming stages. Sometimes installers employ fans, heaters and dehumidifiers to speed up the drying process. Under the proper conditions, a floor could be completed and ready for use in two weeks, but three to four weeks is not uncommon.

Toxicity and flammability: More people are becoming concerned about toxic materials in building products, such as glues, polymers, preservatives and flame retardants. Earthen floors are a natural, non-toxic flooring option; the main ingredients come from the earth beneath our feet. The oils used for sealing, while extracted from natural ingredients, do contain some volatile organic compounds (VOCs). Once the VOCs have evaporated (this takes one to three days), they no longer pose any risk to the inhabitants, but any adjacent occupied rooms should be sealed off during the oiling and drying process. Earthen floors are naturally non-flammable, and are good options for areas around stoves and fireplaces.

Testing an Earthen Floor Mix

Many earthen floors are made from locally sourced and processed ingredients. The basic ingredients are sand, clay soil and a short natural plant fiber (chopped straw is a common choice). Sand is the main building block, giving the floor its strength. The fiber provides tensile strength to minimize cracking, and an aesthetic touch. The clay is the binder that sticks it all together. There is a lot of flexibility in the recipe for a floor mix, but good testing is critical to ensure a successful installation.

Start the testing process by making several batches of sand and clay soil mixed together in different ratios. Earthen floors are mostly sand. The final recipe will depend a lot on the amount of clay in the soil; if it is very clay-rich, you will need to add a lot of sand to compensate. Try starting with three test batches with different clay-to-sand ratios, say 2:1 (sand to clay), 3:1 and 4:1. For each test, carefully measure the ingredients into a bucket, mix them dry and then add water slowly until the mix reaches a thick but spreadable consistency like cake batter. Use a wooden float to spread the mixture on a stable surface. Each test patch should be about ¾ in. (2 cm) thick and at least 18 in. (45 cm) in diameter. Smooth it with a steel trowel and allow it to dry. Repeat this process for each of the other tests, carefully labeling the ratios of each.

When the test patches are dry, check them for cracks, dusting and durability. Cracks are caused by the shrinkage that naturally occurs when clay dries. If a test patch has a lot of cracking, the clay content is too high. If sand grains easily come loose when the surface is rubbed, this is an indicator of too little clay. Finally, the test patch should be resistant to scratching with a fingernail. You will be able to mark it, but it should not crumble away as it is scratched. A surface that is too fragile indicates low clay content.

Once you have determined a good sand-to-clay ratio, make new test mixes with fiber added. Try several tests with fiber content ranging from 10–20 percent of the volume of the clay/ sand mix. The “right” fiber concentration is mostly personal preference. Fiber in the floor will affect workability and aesthetics. More fiber makes the mix harder to spread and smooth out; too little could mean a weaker floor. Chopped straw is light in color and contrasts against the darker background of an earthen floor. The more fiber, the more this effect will be visible. Once a suitable recipe is determined, do a final round of testing that includes burnishing, oiling and waxing, to see what the finished floor will look like.

Mixing and Pouring the Floor

An earthen floor needs a stable, strong and level subfloor. Subfloors that settle or flex will eventually cause cracks in the finished floor. If it is a wood-framed subfloor, cover the wood with a vapor retarder to prevent damage from moisture during the installation process. Insulating under the subfloor is highly recommended to improve energy efficiency and occupant comfort. The insulation material must be strong enough to support the weight of the floor above without shifting or compacting over time. Typically, a high-compressive-strength rigid foam insulation is used. Unfortunately, there are few good natural options. Pumice rock has been used with some success. Straw or straw-clay combinations are not recommended.

Before beginning the pour, protect any surfaces in the room that could become damaged or dirty during installation. Set up fans and dehumidifiers for drying in advance. Determine how thick the floor will be and mark the walls with a line to indicate the finished height. There are various methods for ensuring a flat and level floor. A laser level is great tool if it is available and the installers are familiar with its use. Other options include screed rails and boards (a technique commonly used for concrete pads), or using a depth gauge (a simple stick with a mark on it) to measure the floor thickness as it is installed. Mixing the floor material is a messy process that is best performed outside. Organize all the materials in a central location and make sure they are processed and ready for use. Determine an appropriate measuring container (usually a five-gallon bucket) and translate the predetermined recipe for that measuring volume.

Mixing can be done by hand in a wheelbarrow or with a machine like a mortar mixer. For small floors, hand mixing works fine. Have two people with hoes stand at opposite ends of the wheelbarrow. Mix the sand and clay first, dry, then slowly add water to achieve a cake batter consistency. Then add the chopped straw, and more water if necessary. If using a mortar mixer, put water and clay in first, and then power up the mixer. Add the sand next, followed by the straw and more water if needed, then dump into a wheelbarrow for transport. For either method, add water slowly until you are confident about how much is needed to make an acceptable mix. It’s easy to make a dry mix wetter; drying out a toowet mix requires adding more dry ingredients in the correct proportions, which can be complicated.

Dump some wet mix onto the work area. Keep the piles of material to a manageable size, about enough to cover a 2 × 2 ft. (60 × 60 cm) area. Flatten the mix with a wooden float. Check frequently for uniform thickness and level. Use a back-and-forth sawing motion to remove small amounts of mix from high areas without making holes in the floor, or add more mix to low spots and blend it in with the flat part of the float. Once a section is flat and level, swipe a steel trowel lightly over the surface to make it smooth and glossy. It should only take a couple of passes. Do not overwork the material! Any irregularities up to 1/16-inch (1.5 mm) deep can be taken out in the burnishing step.

Burnishing, Oiling and Finishing

Burnishing is the process of polishing the still-damp floor with a steel trowel to further smooth and compress it. This step is not necessary, but it will improve the final appearance of the floor. Burnish within 24 to 48 hours after pouring. The floor should still be damp but not too soft; if it’s possible to make a trowel mark deeper than about an 1/8 in. (3 mm), the floor is still too wet and needs more time to dry. Once it reaches the necessary stiffness, carefully walk out to the far end of the floor, using foam pads or steel floor pans to spread your weight. Mist down a section with a spray bottle and smooth it out by applying pressure with a steel trowel. The surface should be shiny and smooth when done. If you find areas that are particularly low, you can add a little more wet mix to fill them out. This is your opportunity to make the floor perfect!

After the floor is completely dry, it can be sealed with a drying oil like linseed oil. Linseed oil is made from flax seeds, and there are many types and grades available. The recommended oils do not contain heavy-metal drying agents and come premixed with solvent to allow increased absorption. See under “Resources” for suppliers. If a premixed oil is not available, mix four parts linseed oil with one part solvent (mineral spirits, citrus oil or turpentine) to make your own oil blend.

Proper sealing with an appropriate oil is what gives an earthen floor its hardness and resistance to moisture. The oil is absorbed by the dry earth mix and polymerizes as it dries, binding the earth together and making a hard and water-resistant layer on top. Keep in mind that the unoiled floor is fragile — walk and work on it carefully! The oil can be applied with a brush, a paint roller or rags. Apply four to six coats of oil in the same day, one right after the other. Do not leave any puddled oil on the floor; clean it up with a clean rag. Make sure the room is well ventilated while applying the oil, and also while it cures, which can take a week or more.

Once the oil has cured, the floor is ready for use. At this point, there are some additional optional finishing steps that can make the floor even smoother and shinier. Many choose to apply a floor wax for added durability and shine. The recommended waxes are fairly liquid and can be applied with a brush or rag. After drying, the floor should be buffed with an electric buffer to remove excess wax. Another optional step is to lightly sand the floor after the oil has cured and before waxing. This leaves a smoother finish.

The earthen floors of today are a synthesis of ancient and traditional practices melded with modern materials and building science. Until recently, the only way to have an earthen floor was to make it yourself. Now, in some parts of the country, there are contractors who offer the technique, and a ready-mix floor product is available to take out some of the guess work for the novice builder. More people are finding that earthen finishes are not merely appropriate for our modern lifestyles, but are in fact a highly desirable choice. They offer all of us the opportunity to experience the joy of living with earth in our homes.

Sukita Reay Crimmel has installed over 20,000 square feet of earthen flooring, and is one of the preeminent experts in the emerging field of earthen floors. She has created a ready-mix flooring product and a line of finishing oils, manufactured under the name Claylin.

James Thomson has spent a decade introducing students to the joys of building with earth with House Alive, one of the leading natural building training organizations in North America. He is an accomplished public speaker and event planner, having facilitated several professional conferences for natural builders.

A Tamped Road-Base Floor

By Frank Meyer

I made my first earthen floor over 20 years ago. I started the process by collecting samples of all the soil types available in our area. After weeks of playing in the dirt, mixing in stabilizers and trying to strengthen and harden the earth to make it suitable for a floor, I came to an interesting conclusion. One particular road base made the hardest, prettiest and quickest floor without any stabilizers at all. Its rich red color and excellent blend of silt, clay, sand and gravel made test bricks that were more impressive than anything else I came up with.

Not all road bases are created equal. The one I chose is what is known here as “city base,” and is approved for building roads and streets in Austin, Texas. It originates in a quarry where the material is taken from the earth and the silt, clay, sand and gravel are separated, then re-blended to specified proportions. By using this material and applying basic road building techniques, we have a big advantage over traditional poured-earth floors. The process uses relatively little water, thereby requiring a much shorter drying time. It can typically be walked on a day or two after installing.

To begin the process of building a tamped road-base floor, make sure the ground is fairly level, smooth and compacted to at least 6 in. (15 cm) below the planned finished floor height. If a vapor barrier is used, spread a layer of sand 1–2 in. (2.5–5 cm) thick both below and above the barrier to prevent gravel from puncturing it. Apply the first layer of road base to a thickness of about two inches and wet it with a hose or watering can, just enough so that the silt and clay stick to the aggregate.

Compact the first layer. A plate compactor, available at tool rental outlets, works well. (Be sure to vent the building with fans if using a gas-powered compactor.) Hand tamping is slower but much quieter and doesn’t produce fumes. Hand tampers are easily made from wood or concrete or by welding a steel plate to a piece of pipe. Hand tamping the edges works best, even if a powered compactor is used.

Repeat layers as necessary until they reach about 1 in. (2.5 cm) from the finish height. At this point, you need to level the floor. Sift the road base through a piece of 3/8 in. (1 cm) hardware cloth to produce a mixture of silt, clay, sand and small gravel. Layer it on and level it out, using screed boards (much like concrete workers use).

After leveling, moisten and tamp the mix again, making sure that it bonds with the layer below. For the top coat, we screen the material again, this time using 1/8 in. (3 mm) hardware cloth. The top coat is not compacted but hand troweled and burnished, using just enough water to make it bond and be workable. The most important thing is to make sure it bonds with the layer below. Trial and error will give you a feel for it. Although many of the floors I have done have no straw in them, adding chopped straw lessens the likelihood of cracking. Getting a smooth, slick finish is more difficult with straw in the top coat, so I recommend chopping the straw very finely if a glassy finished is desired.

Traditionally earthen floors were sealed with fresh blood from a cow or ox, but most builders today use boiled linseed oil or tung oil to seal the floor so it will not dust up, and it can even be cleaned with a damp mop. The floor must be thoroughly dry before sealing or the finish may turn cloudy, or even moldy in a moist location. I like to put no less than six coats of oil on, making sure each coat is totally dry before adding another coat. There are now many commercial products available for sealing that may even dry harder than linseed oil, but they are more expensive. Consider using them only for the final coat. With time, patience, lots of hard work and an affinity for getting dirty, anyone can do this. Enjoy!

New Building Materials

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by Martin Holladay from Fine Homebuilding and Green Building Advisor

My first reaction was, “Product choices don’t matter very much.”, because it is ecologically more appropriate to renovate/reconstruct an existing house instead of adding the footprint and expenses of a new one.

Why do we build green homes? To reduce our carbon footprint (because we care about global climate change). To lower our energy costs To ensure that our homes are healthy.

mh4My observations on the new-home market are not so rosy:

  • New homes are often leaky.
  • New homes are full of bump-outs and crazy roof designs.
  • New homes are haphazardly insulated with fiberglass batts.
  • New homes have leaky ducts in unconditioned attics.

What is more important than the choice of building material are these 5 principles to follow:

  • mh3Making sure your house is small
  • Having a compact shape without bump-outs
  • Orienting your house to the sun; making sure that 50% of your windows face south
  • Creating a very tight thermal envelope and
  • Adding plenty of insulation

However, there are 8 (relatively) new green building products:

  1. mh7Zip sheathing (le revêtement mural intermédiaire Zip); It’s easier to put the air barrier at the sheathing layer than at the drywall layer.
    Advantages: Resists moisture better than ordinary OSB; Once taped, the sheathing is as weatherproof as asphalt felt or Tyvek; It’s an easy way to get an airtight building envelope.
    Disadvantages: It’s still OSB; It isn’t vapor-permeable.
  2. mh8Air sealing tapes (bandes d’étanchéité);
    European air sealing tapes manufactured by Pro Clima and Siga (Siga Wigluv) are available from:
    475 High Performance Building Supply or Small Planet Workshop
    They really work; i tested them and the Siga Wigluv tape proved to be the best.
  3. Triple-glazed windows (fenêtres à triple vitrage); they are very good event though they have 2 drawbacks: increased cost and lower SHGC (solar heat gain coefficient), because they insulate much better (consider that in winter the heat loss is bigger than the heat gain because the sun shines only 5or 6 hours per day…
    Triple-glazed windows don’t just lower your energy bills; they also improve comfort. Because all cold surfaces drain radiant heat from your skin – if the inside window pane of a triple-glazed window is warm it won’t do that.
    The best choice are Fiberglass windows are manufactured by:
    Accurate Dorwin, Manitoba
    Duxton Windows, Manitoba
    Entreprises Marchand Portes et Fenêtres, Québec
    Fibertec Windows, Ontario
    Inline Fiberglass Windows, Ontario
    Thermotech Fiberglass, Ontario
  4. Cellulose and mineral wool insulation (les fibres de cellulose et la laine minérale);
    Cellulose has low embodied energy; and dense-packed cellulose reduces air leakage rates.
    Mineral wool is denser and more fire resistant than fiberglass; mineral wool insulation can be used under non-load-bearing slabs.
  5. Roofing alternatives
    1. Recycled shingles, perhaps the “greenest” — of all roofing products are shingles made from recycled waste materials, such as plastic, rubber, or wood fiber. ($3.15/sqft meterial)
    2. Wood shingles from Maibec Industries ($6.65/sqft material)
    3. Slate and Clay tiles from Durable Slate ($9.20/sqft material)
    4. Metal roofing ($4.20/sqft material + $6.53 for labor)
    5. Recycled (tire) rubber roofing
  6. Ductless minisplits (les mini-thermopompes bibloc à haute efficacité sans conduits)
    For energy-efficient homes in New England, using ductless minisplits for heating and cooling is now very common. Main manufacturer is Mitsubishi.
    In some cases, only one or two minisplits can heat the entire house. They have low heat output ratings (10,000 to 12,000 Btuh) which are a good match for superinsulated homes.
    They use electricity for fuel, which means: There is no combustion in the house; They work well with PV.
  7. mh9Drainwater heat recovery devices (système de récupération de chaleur des eaux de drainage)
    (Almost) Every new house should have one.
    Difficult to install in single-story homes with slab foundations.
    These devices work well for families that prefer showers – but not for families that prefer baths. These devices have no moving parts. They are very cost-effective in homes with electric-resistance water heaters. However, they are less cost-effective in homes with natural gas water heaters.
  8. PV systems (les systèmes photovoltaïques)
    Prices keep dropping.
    Since Québec has low electricity prices, this province is relatively unaffected by the PV revolution. This technology is deeply disruptive. My first PV module in 1980 cost me $8.33/watt.
    The cost per watt is now under $1.
  9. LED lighting (appareils d’éclairage à diodes électroluminescentes – DEL)
    The light quality is quite good.
    These lamps are now affordable.
    They are efficient and long-lived.
    The price of these lamps will continue to drop.


Construction Materials

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Nanobio helps to make construction material less toxic; it also reduces or binds volatile chemicals:

paintLoosen wallpaper
• mix 1/2L Nanobio + 18L water
• apply to wallpaper with large brush
• let rest 30min
• apply again with large brush
• let rest 30min
• strip wallpaper

Gluing wallpaper
add 3Tbsp EMx ceramic powder/250sqft floor surface into the wall paper glue
• add 500ml EMa

Wall paints
• add 250ml EMa into 20L paint
• add also 600ml EMx ceramic powder

Oil based paints
• add 3-5vol% EMx ceramic powder to the paint
• to prevent volatile organic substances

• mix 1 part EMa + 1000 parts water
• use this mix to make plaster, stucko, etc
• add EMx ceramic powder when using big amounts

Concrete preparation
• mix 100g EMx ceramic powder + 80-100L water
• let sit for 2 days
• prevents cracks, faster curing, corrosion of armature


What is lime?

Lime is the predecessor of Portland cement, and is manufactured by heating limestone. It is can be purchased in two forms: Hydraulic lime, a powder which you need to mix with plenty of water and leave to soak for about two weeks until it looks like yoghurt, and slaked lime, a wet putty that has already gone through this process.

One thing to be aware of when using lime is that it’s caustic, so you need to wear gloves. But apart from that, it is everything that Portland cement isn’t: Namely, beautiful, breathable and best of all, carbon neutral.

9 Ways to Use Builders’ Lime

1. To offset the greenhouse effect. Unlike Portland cement, which is currently one of the top two largest producers of CO2 (huge amounts are produced in the manufacturing process), lime is carbon neutral. It is produced at lower temperatures than Portland cement so uses only about 20% of the energy to manufacture. But best of all, lime reabsorbs the CO2 during its lifespan.

2. Earthplaster. For those building with mud in wet climates, lime is your best friend. Unlike Portland cement, lime breathes, so it doesn’t trap water vapour. When added to earth plasters, lime allows the damp to escape from the walls fast, preventing rising damp, mold and unstable plasters.

3. Lime wash. Lime wash has been used as a paint for centuries. Nowadays you can also colour the wash with natural pigments. The beauty of using lime on walls is that it’s non-toxic, allows your walls to breathe and creates magical interiors. It also repels bugs and prevents mold.

Here’s how to make a simple lime wash:

• 3 litres of slaked lime
• 200ml of white glue or salt (this helps fix the lime)
• natural colour (if desired)
• Water to thin

Mix all ingredients well until a smooth milky wash is created.

4. Pesticide and insect repellent. I can personally attest that a lime wash deters all manner of insects. Before I applied it to my mud plaster, mining bees were carving holes out of my walls. I’m happy to say they never returned post lime wash. Lime takes care of fire ants, wood ants, mites, aphids, flea beetles, and even mosquitos according to some sources. Lime wash can be applied to chicken coops, sheds, or sprayed on your garden to keep your plants bug free.

5. Putty If you drain off the excess water, slaked lime is putty-like in texture. You can then use it to fill in gouges in your plaster or smooth over cracks.

6. Limecrete Limecrete can be bought in slabs, or made and poured. Hydraulic lime is mixed with sand (and sometimes pozzolans) to create a durable surface. Limecrete can be used for floors, foundations and as a wall plaster, and is often preferred to Portland cement because it is breathable and reduces interior humidity.

7. Hempcrete Hempcrete is the natural building material of the moment. By mixing hemp, lime, sand and water together and allowing it to set in molds, a sturdy block is formed. These blocks can be used for wall construction. Hempcrete has also been used to create floors.

8. Fungicide and Disinfectant Lime is antifungal and a mild disinfectant. It prevents mold growing and is therefore perfect for walls that see damp or any area prone to bacteria.

9. Food preservation When I first heard a friend of mine saying she was going to dry eggplants with hydraulic lime to make eggplant jam, I was doubtful. “You taste it,” I said. ”I’ll stand by to call the ambulance.” In fact, the art of dehydrating food using lime is practiced in many countries, and often makes the food more delicious in the process.

One last word on lime: It’s very inexpensive.