Tiny Home subfloor, proper layers for long lasting system
I have seen multiple techniques out there being used regarding how the “builders” are stacking the layers for weatherproofing and insulating the sub-floors on the trailer of a tiny home. I believe the variety of solutions being used are sometimes letting the maximum trailer height dictate alternative building techniques, which are possibly sacrificing structural stability over the long term. I’ve read that the builders are applying metal pans to underside, some to top side, some are adding a 6-mil vapor barrier atop of this, then adding plywood or OSB, or doing insulating within the steel trailers sub-floor, etc…
I’m looking for a straight forward path to doing this correctly every time. For me, simplest solution is a SIP system atop the trailer, and not bothering with working on the underside of the trailer, its just more trouble than its worth.
I think the “experts” agree with utilizing a SIP system (bottom layer of AdvanTech 23/32 floor panel, 3.5″ rigid foam, then 23/32 plywood, for example). My suggestion is regarding the additional layers done prior to the SIP placement (or if they are even necessary).
Would it be appropriate or necessary to cover the top of the steel trailer platform with a thin grade aluminum sheeting prior to attaching the SIP? My proposal was to use 36″ wide .011″ gauge Al sheets which the overlaps are sealed using a ASTM C1311 rated sealant. You would essentially have a barrier system in place to prevent moisture intrusion to the subfloor from underneath the trailer under normal road driving conditions in snow and rain. With the AdvanTech panel atop of this, it would be nearly bullet-proof.
If it was me, I would extend the flashing a few inches beyond the trailer foot print so as to wrap it up the SIP sides, and then a final flashing layer would be applied atop the periphery of the SIP system so as to run down the SIP’s sides, overlapping the underside. This would prevent any moisture from running down into the trailer’s aluminum floor pan and getting trapped.
Is this even necessary? Or is the simple solution going with the AdvanTech flooring panels for the bottom of the SIP and leave it at that to handle the road conditions? I am looking at this from the aspect of longevity. My building practice would be one that says I can guarantee a home 50 years from rot if it was up to me!
Would the aluminum pan become the vapor/air barrier in this case, and the SIP my insulated floor system to reach the desired R value? This to me seems like an air tight, moisture free solution.
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