Remodeling a 1990’s straw bale home
I’m hoping I can get some advice on a remodel project I am doing in Plainfield, VT (zone 6A) to a 1990’s straw bale home. The original scope of work was to replace the worn out windows with new Kohltech triple pane units. I knew this was going to be a challenge as the house is covered in a cement based stucco on the exterior. There are few if any examples of stucco around here and seemingly no pool of talent to draw from, or at least that I have managed to access. My crew and I have been grinding out the stucco using angle grinders with diamond blades to free up the nailing flange. So far so good.
We’ve ground out 10 windows so far and two have advanced rot in the rough window bucks which are an inconsistent assemblage of plywood and 2x material. These two windows are inscrutably under the covered porch which appears to be sound and dry. The porch rafter ledger is let into the stucco a varying amount (wavy walls, after all) but didn’t ping my moisture meter above 14% moisture content (MC) at it’s worst. The rough bucks topped 50% which is when my inexpensive meter calls it quits. One window (the worst one) is within spitting distance of the upstairs bathroom, but we ran the water in the shower, sink, toilet, for a long time with no increase in wetting. We also have had some decent rains which didn’t worsen anything. Finally, we’ve attacked the sides of the house that we didn’t think had any moisture issues. The worrisome walls we have yet to grind into. There’s 26 windows all told.
The other window bucks have been okay thus far. Some rot primarily in the sills, but more easily repaired. The windows were installed to what I recall as being “best practice” for the time. Caulked flanged, felt paper wrapped into the rough opening. No tapes. No sill pan like we do nowadays.
So. Issue 1: I am not an experienced stucco plasterer. I know I need to grind a lot more stucco out to chase the moisture source and solve it as best I can – assuming I can pinpoint it.
Issue 1.1: There’s not a wealth of knowledge locally to repair or maintain a stucco structure around here, so overtime whenever these folks suffer from a maintenance issue they are going to bump up against this again – even if I gain some measure of competency in stucco repair after this I might be busy, injured, moved to wherever the Sam Hill… I don’t want them to be vulnerable to having only me to turn to if and when an issue creeps up; that’s not a sustainable situation for them or me.
Issue 2: The stucco was applied by volunteers and well-wishers, so has it’s share of hairline cracks and lacks for a weep screed, which certainly raises a flag for me. I think. I am no expert on this. The stucco was also gone over with some kind of elastomeric coating to, I think, bridge the cracks? It seems to have worked in some areas, but not very well overall.
Extreme fix proposal:
Remove the stucco, install vertical sleepers (maybe 2×4’s on edge?), insulate (cuz why not?) with dense packed cellulose or rockwool, sheath with air sealed 1/2 plywood & WRB or taped Zip System OSB, rainscreen, and reclad the house with something within the local talent pool (e.g. shiplap; clapboard; shingle; etc.).
This strikes me as an expensive fix. The clients are committed to the house and the land, and I wonder if this might actually save them money in the long term since repair and maintenance will be a cheaper proposition if folks know how to disassemble and reassemble the cladding system easily.
I would appreciate any and all thoughts you all have regarding this. I like taking on jobs that push my out of my depth so I can stay on my toes, and this one is certainly no exception! I want to guide these nice clients down a path that will make their life easier long term, but don’t want to bleed them dry doing it.
I would also welcome any stories anyone has about remodeling the exterior walls of straw bale homes in general.
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