I have a detached garage/shop that is metal. A portion of it is framed in and has insulation and drywall as well as a concrete floor, about 350 square feet. I would like to turn it into a man cave or 1 bedroom apartment. Would there be any issues if I redid the whole interior with cob over the drywall and added a rocketmass heater. Examples are putting up cob walls, building benches, etc as well as installing a bathroom. Essentially having a pure cob inside. Would I run into any issues with this. Breathing issues, moisture buildup issues or any unforseen issues. Thank you all in advance for any help.
The foundation is the only potential issue since you will be offset from the footing, a mono-slab less of a concern....If it is a 2500 PSI slab on grade knocked down for age to 1500 PSI the weight is not an issue. COB @ 8" thick x 8' tall would bear down about 5-10 PSI, but flex or deflection can be an issue. If your slab(assuming you have one) is suspended by rebar and does not bear on the ground less of an issue(probably not the case). If is not and the substrate soil cannot support the deflection from additional weight there could be serious issues at the adjacent connecting walls. Concrete slabs can deflect around 16-20% that adds significant bearing & shear load to sub soils, walls go with it that is why we put real high compression strength and rebar in them since they do not do well in bending.
So the weight itself may be of little concern but the weight distribution may be of high concern especially if the corners/walls are already showing signs of failure.
I cant tell you much on the concrete pad itself as i did not put it in. It was already installed when i bought the house. I appreciate the information. I will do some more research and see what i can come up with. Do you have any insight that would help me solve those issues you listed?
Yes, lay down a 1/2 thick concrete protection board on the slab below that put Roxul mineral wood board 1.5 thick R 6 "COMFORTBOARD IS" as insulation and capillary break....Both will help distribute the load over the entire length of the wall and reduce your risk. Start laying COB on top of that. If against drywall prime it with ROMA Biogrip to provide shear resistance.
There is no more risk in having a COB exterior in your climate zone than wood COB may even be better and cost less. I'll look at it more later got to get to work. I'd lay down a 1" thk Type S lime mortar under that mineral wool instead of plastic most would use.
I would love nothing more than to have a cob exterior but i thought in my climate i would run into insulation and moisture issues. I live in Wyoming where it can get down to -30 temps, strong wind, and a ton of snow. Thats why i was thinking just a cob interior and i happen to have that framed in portion of the metal building that i could use.