Add cross-framing under toilet?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by speede541, Jul 21, 2010.

  1. speede541

    speede541 Member

    Messages:
    124
    Location:
    San Francisco Bay area
    As part of my little project I'm replacing a small square of rotted floor under a toilet -- a double layer of 3/4" ply, in fact -- spanning about 14" between parallel joists.

    Do any of you routinely install cross bracing to span between the joists for a bit of extra support under the toilet? It seems pretty beefy without, but I'm curious about best practices.
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,313
    Location:
    New England
    Ply is strongest if it spans at least two bays (i.e., attached to three joists). So, since you'll have some edges unsupported, consider blocking along those edges.
  3. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    I agree with jad's comments. I have found over the years, that for a drywall repair, or a flooring repair....a bigger patch is actually easier, stronger, and ends up better on the cosmetic front.

    A 14" square of plywood, just supported by a 3/4" lip at the joist, will be prone to sag along the open edges,and pry up on the supported edge.
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