Drywall (a.k.a. Sheetrock, plasterboard, gypsum wallboard) is king. The average 2,000 square foot North American home today has over 16,000 lbs of the stuff making up its walls and ceilings!1 But for those of us building with materials like straw bales, light-clay straw, wood chip clay, hempcrete, cob, or those looking for options to include in more conventional “green” homes, the big question is, does drywall provide the best option for interior walls? To answer this I think it’s important to look at it from three angles: 1) What is drywall and how has it come to dominate, 2) What are the environmental and health impacts associated with drywall, and, 3) Is it compatible – both logically and aesthetically – with the other materials in the home. We’ll finish the discussion by looking at the alternatives to this ubiquitous material.
The Ascent of Drywall
Drywall hasn’t always been king. Developed in 1916 by U.S Gypsum Company (USG), this rather simple mixture of raw gypsum (calcium sulphate dihydrate), water, and other additives was pressed between heavy paper under heat (up to 500 degrees F) and pressure. Originally called “Sackett Board”, the gypsum board started as small tiles before it evolved into the larger 4′ x 8′ sheets we’d recognize today. Its use surged as America’s involvement in WWII intensified, thinning out the labour and creating a demand for quick and inexpensive building materials to offset the labour shortage and war costs.
You see, prior to drywall, lath and plaster dominated peoples interior lives. It did so for hundreds and hundreds of years.
Thousands of wooden strips (laths) would be covered with multiple coats of wet plaster, typically lime, gypsum, or sometimes cement. The work required considerable skill and was comparatively labour intensive, mostly because multiple coats of plaster were applied to the laths, each layer needing to dry before successive layers could be troweled on.
Drywall, called so because the drying was done in the factory, sped things up, reducing the time it took to finish a wall by 90%, as compared to lath and plaster.2 This speed, along with ease of use, and standardized dimensions, has positioned it as one of the most widely used building materials today, with 97% of homes in North America relying on drywall.
Drywall, The Planet, And Your Health
Being made up of rather basic, mostly inert components, drywall is a rather benign product.3 Although from an energy perspective things look a bit different. By weight, drywall is about half as intensive as plywood to manufacture, and about 24 times more intensive than straw bales.4 Looking at the life cycle (impacts from cradle to grave) of drywall, there are associated impacts with mining gypsum, its transportation and manufacture, and of course, its disposal. Mining is inherently disruptive to habitat, and between mine, plant, and building site, transportation is often hundreds if not thousands of kilometres (here’s a map of the plants in N.A.). The main impact, however, is the manufacturing – the crushing and milling, blending, pressing, paper making, cutting, heating – accounting for approximately 80% of the energy used to get drywall into the home.5 And let’s not overlook drywall waste.
Between 12% and 17% of drywall is discarded as it is cut and fit during the installation process, amounting to 26% of all waste from new construction, or about 3,000lbs of waste per residential home.6,7
Of course drywall can be recycled, either made into new drywall or ground and added into the soil, but only a miniscule amount actually is. And when put into the landfill, hydrogen sulfide (H2S or “sour gas”) can be produced where water is present, thus creating liabilities for landfill managers.8
Most drywall manufactured today uses virgin gypsum, though the trend is towards synthetic gypsum, a byproduct of coal electricity generation. Synthetic gypsum now represents 45% of gypsum used in drywall manufactured in North America.9 Though this seems like a big win, nothing could be more important than doing away with electricity from coal-fired generating plants. If this happens, and let’s pray it does, we’re back to gypsum mines for making drywall. Besides, most of the impact from drywall is not the mining but the manufacture, so let’s not be blind to the situation before us.
Now looking at drywall from a human health perspective, there are two things to watch for: 1) The very fine dust created when drywall is cut and when the joints are sanded is a lung irritant that can lead to serious health problems and should not be inhaled, 2) The joint compound or “mud” used to conceal the joints may contain formaldehyde and aldehyde, and biocides to increase shelf life and to retard the growth of bacteria and mould.10
Though not yet available in Canada, Murco’s M-100 is a hypoallergenic, “earth-friendly” drywall mud free of the aforementioned additives. Drywall is also biologically active (which I don’t consider a bad thing), so keeping it dry and controlling indoor humidity is important to ensure mould does not become a problem.
Now suppose you get your hands on a “greener” (recycled or synthetic) drywall, use a healthier drywall compound, keep the dust down, and discover its coming from a manufacturing plant near to where you live, is it still the best option for interior walls?
Suppose you’re building a straw bale home. The thick exterior walls are going to keep you cozy year round, with a minimal amount of heating or cooling. You dream of the deep, undulating walls, with light dancing in across softly textured finishes through beveled window reveals. Then your focus shifts to the interior walls. You think, “It seems a waste to use bales inside, as I’ll lose 18” of floor space to the walls. Maybe I should use something thinner.”
Most people think straightaway that when it comes to interior walls thinner is better.
But let’s back up for a second and ask ourselves what exactly an interior wall is for. If you ask me, it has many functions: comfort (think zone heating – the option of heating/cooling certain rooms at certain times), privacy, soundproofing, thermal mass, fire protection, built in furniture (maybe a bookcase), or to be art, and not just something to hang art on.
The other thing you should think about is what the space will feel like if a stiff, straight, flat wall is run up against those beautiful “deep, undulating” straw bale walls. You may realize, as architect and natural builder Bob Theis has, that “it creates conflict.”11 Nature is curvy, irregular, asymmetrical, knotty, unique. This is partly what may have led you to building with earthen materials in the first place. Compatibility, then, is determining what your needs are and how they can be brought into balance through the materials you choose to use.
Making Drywall “Flow”
My intent is not to disparage anyone using drywall, only to demonstrate that there’s more to thinking about walls than what we’re often told.
If drywall is chosen, one trick that helps to balance the flatness of it, especially in the context of pairing it with more organic natural building techniques, is to use clay plaster over the drywall instead of paint.
We’ve done this on several projects and have had very pleasing results. Tracy Thieriot, owner of California-based Ochres and Oxides, gives drywall “flow” by adding raised clay features on the drywall to create an undulating base for the plaster, thereby helping to bring a better balance to the surfaces.
Now let’s look at each of the alternatives more closely.
A mixture of clay, sand, and straw, cob can make excellent, beautifully organic interior walls. Though exterior cob walls are often 12 inches or more thick, I’ve seen interior walls as thin as 4 inches. As cob is made in place, it can be sculpted to your heart’s content, providing incredible flexibility of form. Cob stores both heat and “coolth”, helping to regulate temperatures at either extreme. In passive solar designs, placed near a south-facing window, cob absorbs heat from the low-winter sun during the day, releasing it at night. Other options include a hydronic radiant wall to create “in-wall heating.” It’s also possible to sculpt cob, or inset patterns, or even built-in furniture into the walls. Of course, cob walls are heavy so care must be taken to ensure the structure can safely bear the load.
Blocks made of clay, sand, and straw (or other fibre), adobes can be made and dried before being stacked in the home. Adobe walls have similar properties to cob, though the walls tend to be straighter. Once stacked and mortared together with, you guessed it, more clay, they can be left as is or plastered over with clay or lime.
3. Lath and Plaster
This technique, though more labour intensive than drywall (though much less so than cob or adobe; and besides, governments always say we need jobs, so one could ask, why take the labour out of it anyway?!), creates a very sound wall. It can be refined with each successive coat and pairs nicely with clay or lime or even gpysum. If a little insulation or soundproofing is required, pair this technique with woodchip-clay (see below).
Using wooden laths to create a cage around standard 2 by 4 framing, bark-free wood chips can be tossed in a slurry of clay, often in a cement mixer or large mixing bin, and dropped into the cavity (no packing necessary). Once dry, the lath can be covered with plaster as described above. Woodchip clay provides insulation and soundproofing, while also providing a nice substrate to plaster.
5. Light-Clay Straw
Light-clay straw is similar to woodchip-clay but instead of woodchips, loose straw is tossed with the clay slurry. Packed into a cavity created with temporary formwork (no lath required), the walls provide a great balance between thermal mass and insulation/sound-dampening. It’s more labourious than woodchip clay but when dry, creates a wonderful surface to plaster onto.
6. Wattle and Daube
Wattle is a woven biological material (wood, reed, etc.) covered with daube – a heavy earthen plaster that adds stability to the wall. This is a very old technique used throughout the world for thousands of years across many cultures. One very effective way to do it is to start with strong, straight vertical poles approximately 2 to 4 inches in diameter, spaced 12 to 18 inches apart, weaving them together with wattles (caragana, hazel, willow, etc.) to create a very strong matrix and base with which to apply plaster. It’s important to secure the vertical poles to the wall’s top and bottom plates, often done by boring a hole with a Forstner or paddle bit into the plates, allowing for a strong tension-fit connection. Utilizing coppice species (those that can be cut, regenerating multiple, smaller stems from the same root system), makes this an extremely ecological building technique, especially when paired with a clay.
Often overlooked these days, wood is a great choice for many interior spaces. Wether planks, tongue and groove boards, wainscotting (strips or panels), old pallet pieces, wood can give a warm touch to many rooms. It may be used on walls and to finish ceilings.
Here’s a link for a few additional ideas.
8. Magnesium Oxide Board
I only mention this here because I’m hearing more and more people talking about it as a drywall alternative. MgO (emm-gee-oh) board, as it’s sometimes referred to, is touted as a green choice due to the fact that it’s an abundant, naturally occurring mineral that is pressed at room temperature (unlike drywall which requires heat). It is said to be resistant to fire, water, rot, mold and termites.
Though these panels look very much like and handle very much like drywall, MgO is almost exclusively mined in Asia (mostly in China) and MgO board is almost exclusively manufactured in Asia (mostly in China). Although less energy may be used in the manufacturing process, it is very likely higher in energy by virtue of how far it must travel. Despite the efficiency claims by proponents off transoceanic shipping, bunker fuel used in shipping vessels is the dirtiest on the planet (just one of the world’s largest container ships can emit about as much pollution as 50 million cars12) and besides, as we’ve already explored, there are other options.
What compels many people to build with natural materials is the opportunity to create a lovely home that is in balance with the natural harmony of the earth, thus acknowledging the future and connecting with their ancestral past. Through memories carried over the winds of time we recognize the shapes, patterns, and textures that made up the places humans called home for thousands and thousands of years. Incorporating these patterns into our homes is what makes them whole. Being present to this, while balancing it with the overtly logical things that guide most of our decisions – time, cost, energy, etc. – is time well spent. We may only build one home in our life, so why not do it the best we can.
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1 Gypsum (2001) By Donald W. Olson – http://minerals.usgs.gov/minerals/pubs/commodity/gypsum/gypsmyb01.pdf
3 LEED: Practices, Certification, and Accreditation Handbook (2009). Sam Kubba.
11 Captured during Bob Theis’ presentation: “Plastering: It’s All In The Details”. September 20, 12. International Straw Bale Conference, Estes Park, CO.