| home | products & services | getting started | techniques | about us | links | contact / place order |
About rendering & plastering... Your unfinished earthbag walls & structures (regardless of your bag material) will not stand up to the ravages of sun and weather. The finishing touch of plastering not only offers enduring protection, but gives you control over the sweeping curves, the texture, and the color that will define your finished structure and enhance its grace, beauty, and longevity. It's important to understand that doing it yourself, with natural materials, is alchemy. There are no cut-and-dry guarantees for perfect results, unless you go for cement or polymer products (or unless you hire a professional, who will likely use those selfsame cement & polymer products). There are variations in temperature, humidity, materials (such as the percentage of magnesium in lime, for example) that can make huge differences in your final results. People who grow up in countries where periodic re-rendering of their structures is necessary (southern Europe, North Africa, South America, to name a few) learn as children. For centuries in northern Europe, the craft was mastered only after a long apprenticeship. The practised individual will just "know" when the mix is right. You'll notice that the outside profiles of your stacked earthbag construction are scalloped, having rounded edges alternating with V-shaped crevasses. Because of this (and, if you're using polypropylene bags, because of their slick texture), you may want to, first, fill in these crevasses with a base earth plaster (roughly equal parts of moistened earth, sand, & straw or cellulose), and then cover your bags with something to improve the adherence of your subsequent plaster layers. Commonly used materials include metal lath, chicken wire, deer fence, and plastic mesh (all available at the big-box home improvement stores). All have their issues; plastic is harder to secure and to get around those interesting curves, while metal requires cutting & has generated some controversy re: electrical fields (click here to read more). Garden staples (6-8" long, commonly sold to secure landscape fabric to the ground) & twine work well to secure mesh to the earthbags. You can also cover the bags with sheet material (landscape fabric, etc.) before adding any sort of mesh to help improve adherence. If sustainability is important to you, you can use burlap sheeting (wetted down) in lieu of mesh. On the other hand, you can just dispense with using any adhering material & simply pile it on (which adds weight and stability). Many do so. It's a time-honored tradition that stretches back into the proverbial mists of time; consider similar structures still standing & being used today worldwide. Like so much else in life, it's all about the inverse relationship between time & labor vs. convenience & cost, and where you choose to draw the lines. What to use? That's up to you. We're not experts (yet) by any means, and once you start looking, you'll discover that there's a lot of discussion & controversy over the pros & cons of various materials. Here are a few popular plasters & renders. It's not unheard of to mix plaster layers, reserving a more maintenance-free plaster for the finish coat (e,g,, two mud plaster scratch coats followed by a final smoothed cement stucco layer). Colors for lime plaster & cement stuccos can be achieved by adding pigments (here's one site we like). Methods range from slathering on by hand & trowels, to pump & spray application with rental equipment. · Earth plaster: basically clay soil, sand, chopped straw or manure, and water. New Mexico Clay has a good line of clay additives (if your soil isn't up to par), and Dancing Rabbit has a very nice page on techniques. Click here for a YouTube video on mud plasters made with food products (and all other aspects of earthbag construction). · Lime plaster: This is a mortar that is essentially lime (a binder) mixed with sand (aggregate) and. water. Complicated to use, very caustic and hard on the skin... so, goggles, gloves, & long sleeves are called for. Beautiful results. An excellent resource is Barbara Jones' book, The Art of Natural Building. Limewash is an easier application to mix & use over a finished plaster. The National Lime Association offers a great article on this here (PDF download). · Papercrete: A mix of Portland cement, paper & water. Sand can be added to the final coat for texture. Rumored to be prone to black mold growth if exposed to moisture (as if that's a problem here in NM?). There's a discussion that touches on it at Autonotopia, while Gordon Solberg of Las Cruces offers his book and DVD, Building with Papercrete & Paper Adobe, here. · Stucco: By contemporary definition, stucco contains cement. It may contain lime (for flexibility), but most stucco used today is basically cement, sand, and coloring. Widely available for purchase (check your big box stores) and for application by contractors. Breathability? This issue often comes up, and may be more pertinent to something like straw bale construction. A wall covering that allows breathability is likely to require more maintenance. We think that a good waterproof outer coat (using lime for flexibility and cement for strength) will best resist cracking from seasonal temperature variations. Screen vents (purchased or handcrafted) can be embedded, if you like. home | products | getting started | computations | techniques | plastering | links | about us | contact |
 |
 |
|
 |
|
 |
|
 |
|
 |
|
 |
|
 |