Is rammed earth waterproof?
Although rammed earth structures are renowned for their long lifespan and general durability, they do require some protection from long-term moisture exposure. Rammed earth isn’t inherently waterproof, but advances in the industry have provided multiple solutions to protect and seal these unique structures. At Aussie Built, we stand behind Australian-developed Tech-Dry® products to protect our rammed earth works.
What if I don’t waterproof?
Although rammed earth has proven it can stand the test of time without modern-day admixtures, it often doesn’t do so gracefully. Damp earth has a number of issues, including mildew or mold, staining, and overall deterioration.
Aesthetically, something you may not consider is efflorescence. This is the leaching of salts and minerals from rammed earth, creating chalky, unsightly water stains on the surface of your walls. While not dangerous itself, it ultimately indicates the presence of potentially damaging moisture.
If you want your rammed earth structure to age gracefully, we can’t recommend waterproofing enough. See our 7-step sealing process guide here.
Wall without Plasticure:
Crumbling wall without Earth Binder:
Aussie Built wall with Tech-Dry Products:
How to Waterproof Rammed Earth
From incorporating a hydrophobic admixture to using a spray-on water repellent, there are several ways to go about waterproofing your rammed earth build. Here are some recommendations of products we trust at Aussie Built.
Plasticure (purchase here)
If you’re wanting to waterproof any rammed earth structure, the best option is to use Tech-Dry Plasticure. We don’t build without it.
Plasticure is a water-based silicone admixture designed to be added to the rammed earth mix during construction. This product makes the structure permanently water repellent throughout and for its lifetime.
Plasticure does require 3 to 4 percent of cement in the mix in order to work properly. Plasticure does not affect the breathability of the rammed earth structure.
Water pooled above Plasticure-treated rammed earth:
Earth Binder (purchase here)
While Tech-Dry’s Earth Binder isn’t primarily developed to waterproof a rammed earth building, it is part of the sealing system and something we highly recommend. This topical sealer helps prevent dusting and crumbling of walls, leaving a smooth texture and enhanced appearance to all interior and exterior rammed earth surfaces. It has the added bonus of some water resistance for kitchen and bathroom areas, but we suggest following the Earth Binder with the Stabilised Earth Water Repellent W to all exterior rammed earth for added protection and surface sealing.
Interior walls of rammed earth structure:
Stabilised Earth Water Repellent (purchase here)
Tech-Dry’s Stabilised Earth Water Repellent W sealer is a clear, water-based silane/siloxane emulsion water repellent sprayed only on the exterior walls of a rammed earth structure. It’s designed to penetrate into the capillaries and make the underlying layers water repellent.
If done correctly, this sealer will help protect outer walls from visible run marks, efflorescence, construction stains and weathering. It dries to a clear matte finish with no film or coating present after application so the wall can still breathe. It is also adds protection of the applied Earth Binder on exterior walls.
Close up of clear matte finish:
Rammed Earth Maintenance
Plasticure alone will repel any moisture from soaking into the rammed earth surface. Additional Earth Binder and Stabilised Earth Water Repellent sealers are recommended as maintenance and applied when needed to prevent dusting and protection of the outer surface finish. Sealers should be reapplied every 3 to 5 years based on weathering and the surface location.
Depending on the weathering to the structure, you may need to clean your walls before reapplying the Water Repellent to avoid locking in any stains. To do this, we recommend spraying a muriatic acid dilution directly onto the wall, being sure to wear the appropriate gloves and protective eyewear. Spray small sections at a time to avoid letting the wall dry throughout the process.
After you’ve saturated the wall, scrub with a sponge to remove any stains. Then soak the wall with an ammonia dilution while the wall is still wet to neutralize the muriatic acid. Finally, spray the wall with a hose from top to bottom while still wet and sponge to remove any runs.
After it’s been thoroughly cleaned and dried, you’ll need to reapply the Earth Binder and Stabilised Earth Water Repellent W to bind and protect the rammed earth for the next several years.
How to Get Tech-Dry®
At Aussie Built, we’re committed to distributing the same products we trust ourselves. Tech-Dry products are essential to the success of our builds and we want to make them accessible to all rammed earth builders. As the exclusive U.S. supplier of rammed earth products for the construction and maintenance of earth structures, you can find the Tech-Dry lineup and more available on our website here at AussieBuiltSupply.com.