What about moisture?
Moisture is the enemy of all builders, regardless of the materials they are using. Fungus (dry rot) will be able to cultivate and bales will start to decompose if high moisture levels (over 20 percent) are maintained over a long period of time.
Vapour barriers are not recommendable with strawbale construction. With a vapour barrier the render will not be able to attach directly to the straw therefore, eliminating the substantially greater structural benefits gained from the bonding of the two materials and also requiring extra wire mesh or similar for the render to attach to.
Protecting your bale walls with an appropriate foundation, generous roof overhangs, intact & well maintained guttering, porches and verandahs and suitable render materials are the most effective ways to avoid direct rain exposure, splash back, and resulting moisture damage to the walls. Well applied, intact, properly maintained and breathable render will also protect the strawbales from moisture damage.
The ability of clay to absorb and release moisture from/to the surrounding air creates not only a perfect and healthy living environment but also helps to maintain acceptable moisture levels within the strawbale walls. Clay is also well known for its ability to preserve therefore, clay helps to protect your strawbale walls from dry rot and other fungi. These are some of the reasons that clay is our preferred choice for rendering. If external walls need extra protection, a more weather resistant lime render finish can be applied.