Interior Stucco and Humidity
1 11 2008
We’ve started doing interior stucco and almost immediately ran into a few stumbling blocks. Number one was the fact that without horse manure in the stucco the mixer didn’t do as good a job mixing the product. Apparently the manure was acting to keep the clay in the mix from clumping together and when we tried to mis the stucco without it all we got was a mixer full of wet sand and hard clay lumps. We would then have to mix the resulting mess by hand, essentially making the mixer useless.
The second issue was the straw bales were starting to mold after we applied slip to the wall. This was much more worrisome than the clay not mixing in. This was the inside of our house where our new born was going to be living and breathing, with mold on the walls! We theorize that there must be mold spores on the straw and that when the wet slip was sprayed onto the walls it gave the spores the moisture needed to bloom. And because we were spraying inside, and much thicker than we did outside it was taking a long time to dry. Laine did some internet researching and we decided to try spraying the walls with pure white vinegar. This seemed to kill the blooms and inhibit the mold from coming back. We also got two dehumidifiers to run full time inside and keep the wood stove going round the clock to help dry things out.
The questions remained as to how we would stop the mold from happening in the rest of the house, and how we were to mix the stucco without having to go back to using horse manure in the mix (which nobody relished the thought of.) The answer to both turned out to be lime. We had switched our clay finish coat to a lime/sand render and still had lots of hydrated lime putty left over, we added about 1 part lime to our 3 parts sand and three parts clay discovery coat mix and found that if we mixed the putty in with the water it actually coated the clay and kept it from clumping! It also is quite caustic and should inhibit any mold growth. We also started mixing vinegar into the water we dampen the clay slip with before applying the discovery coat and will be adding some diluted lime putty to the remaining slip we need to spray.
When you are building a strawbale home for the first time, these are the sorts of unexpected snags you run into every step of the way. I am not exaggerating when I say we have had to overcome a seemingly impossible problem with each step int he building of our home. And yet we have overcome each of them and learned from them. Whether we will ever put those lessons to good use by building another strawbale structure seems unlikely now, but we certainly will be able to give some good advice to those who may need it!
