Tiny house undercarriage
I have read several threads about tiny house subfloor assemblies. We like the idea of a “DIY SIP” with 4″ high density EPS sandwiched between plywood. This will sit over the 16″s oc steel cross members of the trailer, with only the bottom layer of plywood extending under stud walls. What we have questions about is how to weather/road proof the underside of this assembly (our trailer has no pan).
We have seen/read many tiny home builders use 1′ aluminum coil lashing. Our first thought was to use this idea but instead of sealing with tape, overlap to allow drainage with a layer of house wrap between the flashing and the plywood. The only way of fastening I can see in this case is to bolt the bottom layer of plywood, house wrap (reinforced with tape at puncture points) and flashing to the trailer cross members, with bolt heads protruding slightly into the foam.
Some advice we received since then indicated that glueing the subfloor to the cross members would allow less flex/creaking floors. Our previous idea doesn’t really allow this but it could be achieved by ditching the aluminum and house wrap and either using pressure treated plywood for the bottom layer and/or some kind of boat epoxy to protect the underside of the plywood. Are there concerns around contact between pressure treated plywood and the trailer or insulation foam? Can you foresee any condensation/drying problems with a marine epoxy? Do you think the aluminum is the better idea? Any comments/critiques/ideas welcome.
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