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Offsetting edge gaps in a double-layer subfloor?


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  • Offsetting edge gaps in a double-layer subfloor?

    Does building code [u]require</u> offsetting the end and edge joints of the two layers of a double-layer subfloor? And if so, by how many inches?

    I'm replacing a layer of warped particle board in a kitchen with a layer of plywood, so that I can install tile (I'm using Ditra underlayment). The tile-prep literature I've read recommends offsetting the edge and end gaps of the two layers, which I've done as much as I can, but I'm constrained by the existing cabinetry in a few places and, as luck would have it, at the threshold between tile and carpet, the edge gaps of both subfloor layers will meet EXACTLY along a 4 ft. span. In order to offset that gap, I'd have to pull up a section of carpet, so that I could insert a larger piece of plywood.

    If I leave the matching end gaps along a 4 ft. span like that, will I be in violation of buidling code or is the offsetting of subfloor gaps just a recommendation?


  • #2
    I guess my question wasn't very clear.

    What I'm trying to find out is whether building code has any requirements for installing plywood underlayment over a plywood subfloor. Specifically, does building code require that the subfloor and underlayment joints be staggered, and if so by how many inches?


    • #3
      I am not certain about code minimum but when i must run underlayment over a subfloor i run the underlayment at right angles. example,,if the subfloor is east by west, i run the underlayment north by south. That minimizes edge joint exposure.


      • #4

        I don't guess I would have ever thought about code implications, but when I did mine, I started w/ full sheets at one end, and against one wall (example, north end and east wall) for the first layer, and at the other end, and other wall for the second layer. Because the floor wasn't exact muliples of 4x8, I automatically had an offset, but I don't remember how much. It was probably something in the 14 - 20 inch range.