Editing Earth shelter (section)

===Waterproofing===
On the outside of the concrete, a waterproofing system is applied. The most frequently used waterproofing system includes a layer of liquid asphalt onto which a heavy grade waterproof membrane is affixed, followed by a final liquid water sealant which may be sprayed on. It is very important to make sure that all of the seams are carefully sealed. It is very difficult to locate and repair leaks in the waterproofing system after the building is completed. Several layers are used for waterproofing in earth shelter construction. The first layer is meant to seal any cracks or pores in the structural materials, also working as an adhesive for the waterproof membrane. The membrane layer is often a thick flexible polyethylene sheeting called [[EPDM rubber]]. EPDM is the material usually used in a water garden, pond and swimming pool construction. This material also prevents roots from burrowing through the waterproofing. EPDM is very heavy to work with and can be chewed through by some common insects like fire ants. It is also made from petrochemicals, making it environmentally unsustainable.

There are various cement-like coatings that can be used as waterproofing. The product is sprayed directly onto the unprotected surface. It dries and acts like a huge ceramic layer between the wall and earth. The problem with this method is, if the wall or foundation shifts in any way, it cracks and water is able to penetrate through it easily.

Bituthene (registered name) is very similar to the three coat layering process only in one step. It comes already layered in sheets and has a self-adhesive backing. Applying it manually is the same as with the layering method, in addition, it is sun sensitive and must be covered very soon after application.

Eco-Flex is an environmentally friendly waterproofing membrane that seems to work very well on foundations, but not much is known about its effectiveness in earth sheltering. It is among a group of liquid paint-on waterproofing products. The main challenge with these products are they must be carefully applied, making sure that every area is covered to the right thickness, and that every crack or gap is tightly sealed.

[[Bentonite]] clay is an alternative that the most environmentally friendly. It is naturally occurring and self-healing. The drawback to this material is that it is very heavy, difficult for the owner/builder to install, and subject to [[termite]] damage.

Bi-membranes have been used extensively throughout Australia where 2 membranes are paired together—typically 2 coats of water-based [[epoxy]] as a 'sealer' and stop the internal vapor pressure of the moist concrete exploding bubbles of vapor up underneath the membrane when exposed to hot sun. The bond strength of epoxy to concrete is stronger than the internal bond strength of concrete so the membranes won't 'blow' off the wall in the sun. Epoxies are very brittle so they are paired up with an overcoat of a high-build flexible water-based acrylic membrane in multiple coats of different colors to ensure film coverage—this is reinforced with non-woven [[polypropylene]] textile in corners and changes in direction.