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PVC 3/4 x 4 be used under basement wall base-plate?

GunnyJ | Posted in Building Code Questions on

Can a PVC board be used under basement wall base-plate in place of pressure treated wood? will it pass code inspection in Pa.?

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  1. Expert Member


    Depending on the situation, building codes call for either a vapour-barrier or capillary-break (like sill-seal) between concrete and regular framing members, or that the framing lumber be pressure-treated. The PVC could substitute for the former, but not replace PT lumber where required.

  2. Expert Member
    BILL WICHERS | | #2

    To add to what malcolm said, you could use the PVC sheet as a capillary break under the PT sill plate, but HDPE is probably a better option -- it's likely to be cheaper. Regardless of which you use, try to get it in black. Black will offer the most UV resistance to any exposed areas, which includes the time it's exposed to the sun during construction.

    If you're thinking of using PVC trim board (and not some kind of thin PVC sheet) in place of pressure treated lumber, that's going to be a "NO" -- PVC trim board is not a structural material.


  3. patrick1 | | #3

    Are you talking about a non-load bearing wall in a basement finishing application...or the sill plate that the rest of the house is framed on? The problem with cellular pvc (e.g., pvc trim) is that it has a lot lower compressive strength than wood so you can't use it in structural applications. See discussion here:

    When I was finishing my basement, I used specialty EPS foam blocks (floodsill) under the sill for most of my walls and 3/4 x 4 cellular pvc under some (instead of PT lumber) and these were both blessed by our building inspector since: 1) the walls were not load bearing and 2) they both satisfy the requirement of creating a moisture proof capillary break between the concrete and the wood framing. We were even allowed to use 3/4 x 4 PVC under the base plate for a small support wall for a stair landing. The 1000 psi compressive strength was way more than enough for that application.

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