Our Domes Are Complete
Sunday, January 11, 2009 7:37 PM
It is a major thrill. We do have some considerations we’re having about plaster and the windscoop, For those reading the details, here’s a summary of our ponderings:
We decided to bring the windscoop up to the top of the sunrise dome instead of the bedroom dome. We did this for 3 reasons:
1) better wind collection up front
2) I want to use the top for a sitting area where I can play guitar, it's a better view at top of main dome
3) and it makes the scoop usable as a 'climbing gym' as were able to keep it large (6' 7 ") end to end as it climbs. But now that it's at top, we have to close it off. We don't wanna shrink it's mouth (keeping the larger at top, smaller at bottom to create air suction), but placing these bags as arches ON TOP of the main dome is a lot of weight (I assume each bag is ~ 800 pounds). While they are flat, they are buttressing - but if we start to raise them as arched bags (to get 'opened mouths'), they become lots of weight. So, our idea is to stop about 3 -4 bag lengths before top and build the mouth our of styrofoam/concrete forms to reduce weight and get a custom 'mouthpieces' on the end of the windscoop.
Plastering and water proofing:
1) At the Cal Earth apprenticeship, I learned to use a water proof primer (Henry 107) that is an ashpalt emulsion. I think I recall it's best applied directly to the bags, prior to a scratch coat of plaster. What I’m not sure is if it’sit best to remove the bag from the 'fortified earth' block for application, or is applying to the actual bag is adequate?
Related to this question, we then apply the actual water proofing 'roof cement' (Cal Earth recommended (Henry 203) to what we primed. Again, my assumption is we'll do this to bags directly, over the primed surface.
Since we are in Mexico and there is no Henry products, I am using a Mexican equivalent - one layer for primer (mixed with water) and then direct application after primed layer. I'll let ya know it's 'veracity' once used.
2) My other question is about long term plaster success. I am working with a Mexican crew - and they have a LOT of experience with plaster. But they also tend toward 'traditional' solutions. My builder thinks we'll get MUCH better longevity if we do a scratch coat of plaster to the bags, to get a roughly 'plumb' surface. Then, this cures for a day or two. Then another scratch coat to build up a couple of inches; then a final finish coat. At Cal Earth, we were taught to that one thick, rough coat application, nice & thick, and then a finish coat is adequate. If I go with my builder's advice, I do 3 coats; with Cal Earth's advice it's only 2 coats. The difference is a lot of time, labor, and cement. Any feedback from experienced hands on this 'bag layer' issue with plastering?