When sealing our walls we really wanted something breathable to allow any moisture or water vapor to pass through the walls. We experimented with soaking nopal cactus that we had planted on the land for 2 days mixing this with clay and using this a paint/sealer. We only used this for internal walls that would not directly get wet. Nopal Cactus is also a delicious superfood that we LOVE! We also used a silicone based sealer that leaves the walls natural looking and breathable. On the exterior we used an acrylic sealer called 5X1 this is very watery and goes on thin.
With the slab finished the walls are going up and up. We are doing a mix of 80% earth, 10% clay and 10% cement in our bags. We did a number of tests on our soil and this mix came up the strongest. It's interesting that in our soil tests that adding more cement (20%) actually made the dried material weaker. So with cement in earth bags more does not always mean stronger and better. We are going for a good stabilized earth mixture that is strong but will still provide good breathability for the walls.
Cob is the most creative building material that I know of. Once you have the mass of the wall for structural strenght, then there are all kinds of ways to make little alcoves, shelves, arches...and...ART! You can build up the wall with cob and then add layers of earthen plaster ...and sculpt! In these walls we put some clear onyx stone to let the sun shine though.
Bugs are a big deal in the tropics..especially when you have a Palapa. The general practice in the tropics is to spray heavy duty insecticides twice a year on your palapa to kill all the bugs. We realize most all the commercial insecticides have super toxic neurotoxins and/or hormone disruptors that can buid up in our bodies and create illness down the road or immediately for people who are more sensitive. It's hard to believe any of the MSDS sheets when some of the harmful effects of these chemicals are not studied for long term ...nor are they studied for the synergistic effect...ie.
When it came time to plaster our home we knew we wanted a breathable earth plaster to cover our superadobe walls. We did some experimentation with clay that we excavated from behind our house. Earth plasters are beautiful but not at strong as cement plasters for this reason it is important to consider your house design before chosing a natural plaster. We designed our house to have large 1 to 1.5 meter eaves over every wall to ensure that the walls would no get hit directly from rain. We also decided to use mortar which is a lime and cement mix to stabilze our earth.
At first we were hesitant to build a super adobe structure in the tropics. Not only are there concerns for humidity and rainfall but with the summertime heat you don’t want to create an oven to live in. In colder to moderate climates you use the thick earth walls of a super adobe structure as a thermal mass that collects heat during the day and then radiates it back into the house during the colder night hours. You do this by exposing certain walls and windows to direct sunlight during the winter months and with proper placement of eaves.