Vapor barrier for exist. basement slab in retrofit- how important is it?
I am designing a “semi-deep” energy retrofit of a house built in 1957 in northeast Ohio, Zone 5. It is located near a reservoir lake. We will be doing significant air sealing and insulation upgrades. The house has an existing basement and we plan to insulate the walls but not finish the space. The homeowner requested that we add interior perimeter footing drains, so there is probably at least some evidence of existing moisture issues. If we don’t put a finish floor in the basement, we don’t have the opportunity to add a vapor barrier to the slab. With the additional air sealing, should we finish the floor just to be able to add the vapor barrier so we don’t end up with excessive humidity in the basement? Should we wait and see what the humidity levels are after the work is done and add the flooring later if needed?
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I think the monitor and treat as necessary is a useful approach, but could prove problematic if the owners have all of their stuff back in the space before some treatment is deemed necessary.
"Finishing" the floor could be simpler than a truly finished floor. An appropriate permeance epoxy paint might be sufficient (though if there is excessive vapor drive, it could cause problems with the paint).
A utility grade floor tile could also be considered, e.g.https://armorpoxy.com/interior/garage-flooring/garage-floor-tiles/