Vapor-permeable flooring materials?
Hi all,
I would like to bother you with yet another question regarding the floor assembly for a tiny house on wheels. Hopefully the answers will be relevant for others as well.
( Skip to question below if uninterested in THOW)
My existing subfloor construction from bottom (of trailer) to top: large sheets of galvanized steel sealed together with urethane to form a continuous pan (should be an air and vapor barrier unless I cut holes in it), 1.5 in polyiso, rockwool filling 2 by 6 joist bays, 3/4 inch ply. The steel trailer (iron eagle) cross members are below the steel pan and the floor framing sits on top of the polyiso though is supported by a rim joist. My insulation, not accounting for joist R, should be about R32.
Assuming that the base of my floor assembly is a vapor barrier, I would think that it’s a good idea to install a vapor permeable flooring over top my plywood to allow inward drying if necessary.
Question:
I like the look and durability of faux wood adhered vinyl flooring but I’m guessing that it would form a second vapor barrier. Does anyone have suggestions for a vapor permeable flooring option? I would prefer not to carpet.
Thanks again!
-Tanner
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Replies
Here's a mid-construction photo to show some of the assembly
Tanner,
You're right about vinyl flooring. It's a vapor barrier.
Ordinary 1x4 or 1x6 pine boards (tongue-and-groove) are vapor-permeable. Leave them unfinished for the farmhouse look, or use a simple oil finish (not too thick) if vapor permeance matters.
By the way, why does vapor permeance matter?
Thanks Martin. My thinking, or rather my interpretation of what I've read on the site, is that there should not be a double vapor barrier. I think that it is very unlikely that water will get into the subfloor assembly in the first place but if it's easy to choose a vapor permeable flooring then maybe it's the right choice? I am not set on any particular solution and recognize my hunch could be completely off. Would love to hear your thoughts on the matter!
Tanner,
Moisture is unlikely to enter this assembly from the exterior. The most likely way for moisture to enter the assembly is when you spill a drink or break a bottle of wine. If you go with vinyl flooring, it will limit moisture entry from that type of spill.
Thanks Martin I was thinking of that exact conundrum. I will go with the vinyl and report back after the house raising cocktail party. Stop by if you find yourself in Northern California!
Got cabinets?
Don't extend the vinyl under the cabinets, and you can expect some limited slow vapor exchange there.