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Old 01-03-2013, 12:19 PM  
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Default Details on how to fix rotten plywood around toilet


A friend of mine has asked me to help them with replacing their floor around the toilet. Do I simply replace the plywood and that's it or should there be some sort of underlayment? Should I use special screws?

The leak is already fixed.

Any advice on the details would be appreciated.

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Old 01-03-2013, 03:31 PM  
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You want to locate the floor joists under good wood and cut the old plywood on the center line of the joists so your replacement will have something to sit on. So that takes care of the sides, the front and back joint wants to be supported too. You can use 2x4 peices on the flat half under the old plywood, screw them in from above before you put your new peice down. 2 1/2 inch galvinized deck screws. You may find some damage on the floor joists too. At the least they should be cleaned up and treated with something to kill the bacteria. If you have lost a little off the top surface you can just scab a chunk of 2x? to the side of the joist.
If you find a lot of damage on the joists come back with photos. Use a tube of floor glue for everthing.

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Old 01-08-2013, 02:50 PM  
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I've lost count of the number of toilets I've reset because of leaking supply lines or wax rings, and have learned a few things. Your mentioning the leak has been fixed implies that the toilet is back in place--if that's the case, it needs to be removed again to enable properly replacing the sheathing under it.

Cutting the original rotted floor sheathing as nealtw suggests is not a good idea, as it only leaves you with less than 3/4" of joist bearing width for the new and old sheathing. Much better to scab on some glued and screwed 2x stock to the joists, working from underneath. Doing so provides twice the bearing area, and will be less likely to damage the edges of new and existing sheathing by having your fasteners too close to the edges of same. I always drill pilot holes at all sheathing attachment screw locations to minimize splitting, and I also make a point of using exterior grade plywood, to slow down the damage rate of inevitable future leaks.
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Old 01-08-2013, 04:27 PM  
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I've done this in a bathroom situation that DID NOT have access from underneath. It is not a big deal to scab 2x material from above (once the toilet is removed) to provide a solid bearing surface for the new subfloor.

I used this as an opportunity to install new tile throughout the bathroom as an upgrade. After scabbig and replacing the subfloor patch, we used Hardie board throughout and tiled per usual. Toilet went back and the folks were very happy. Insurance settlement paid for most of the work and their portion was quite reasonable.
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Old 01-08-2013, 06:39 PM  
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Do they make a water resistant wood substitute of the proper thickness for this location?
You can almost count on a new leak eventually.
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Old 01-08-2013, 06:51 PM  
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Bridgeman; scabing on the side of the joist is an option, but plywood always want to share one joist if possible even when you have a house with double joists. When you sheet a new house, at the transition over a bearing wall you have to scab on the side for a foot or two every eight feet and that's where problems will show up when the scab shrinks more or less than the joists.
Just for kicks some time try to find 1/2 or thicker plywood that isn't made with exterior glue, but it really dosn't make much difference anyway if water gets to the plywood it still swells up causing problems.

Last edited by nealtw; 01-08-2013 at 06:55 PM.
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Old 01-10-2013, 07:06 PM  
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I've never seen a plywood with or without exterior glue that can withstand any real water leak without swelling up and causing havoc.

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