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Replacing a Rotted Floor Under the Toilet

Minor wood rot around a toilet flange doesn’t always mean you have to replace the subfloor. Solve the problem with a metal flange support instead.

By the DIY experts of The Family Handyman Magazine

Replacing a Rotted Floor Under the Toilet

Minor wood rot around a toilet flange doesn’t always mean you have to replace the subfloor. Solve the problem with a metal flange support instead.

Install the flange support

If only the area directly below the flange is rotted, you can install a two-piece steel closet flange support. It goes under the flange and transfers the load of the flange and toilet (and you) out onto more solid surrounding wood. But if your floor is severely rotted, say more than an inch beyond the flange, you're stuck replacing the flooring around the toilet.

Flange supports are available at home centers and plumbing supply stores for either cast iron, plastic or brass flanges.

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Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

    • 4-in-1 screwdriver
    • Adjustable wrench
    • Corded drill
    • Drill bit set
    • Rags

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.

    • Metal flange support
    • Stainless Steel screws
    • Wax ring

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September 05, 8:08 PM [GMT -5]

This works if the damage is minor and the toilet base is the correct distance from the closet flange for the wax ring to make an effective seal. If the subfloor has rotted from water leaking from the base of the toilet it is likely that the distance from the base of the toilet to the closet flange is not correct and this also should be addressed in the repair.

Alternately if the subfloor has a second layer of flooring that was put in place to raise the surface of the bath floor with the linoleum to sit flush with the adjacent carpeted areas of the home, then this layer can be removed (most easily with a 4" right angle grinder and a $15 diamond cutting disc (see blog on holepro website).

If you know in advance the amount of gap to correct you can special order a spacer of the correct thickness. The other option is to buy four or five plastic spacers from the local building supply store and use adhesive caulk between each layer or you can cut a wood donut of our a piece of exterior grade plywood and use that as a spacer to build up the floor so that the closet flange sits proud to the linoleum. This last approach works well if the linoleum has been replaced with much thicker floor tiles.

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