Rot in subfloor


Old 04-11-07, 07:25 AM
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Join Date: Jan 2007
Location: Long Island
Posts: 9
Rot in subfloor

I have 2 small areas, about 6" x 6" (front left and right corners) next to the shower pan, where the top layer of the subfloor (5/8" ext ply)rotted away because of water leaks.
In one spot there is a 1/2" hole where a knot rotted and fell out.
the plan is to level the floor with a cement self leveling product, lay down durock cement boards, and ceramic tile over that.
My questions:
Is the rotting process stops when the reason for it is eliminated?.
Do those sections need to be replaced?
If I don't replace them, is there an alternative?
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Old 04-11-07, 07:44 AM
Join Date: Aug 2000
Location: USA
Posts: 15,834
Cut out and replace affected areas. This will give you an opportunity to inspect for additional damage below. You want to be sure rot has not extended to joists and if any repairs are required in them. Some say rot spreads like cancer.

Eliminate the source of moisture from shower pan. Is shower pan leaking? Is moisture coming from leaky shower door or curtain? Leaky shower pan is far more serious than a leak around shower door or curtain.
Old 04-11-07, 07:48 AM
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>>Is the rotting process stops when the reason for it is eliminated?

Yes, "dry rot" is usually a misnomer when applied to situations like this. If the leak has been repaired, the wood will not decay provided the humidity stays below 60%.

>>Do those sections need to be replaced?

It depends on whether the integrity of the surrounding area has been compromised. If the rotton patch is causing the surrounding area to deflect when you step on it, then yes, it likely should be replaced.

>>If I don't replace them, is there an alternative?

If you can access the floor from below, you could install some perpendicular blocking between the joists to at least shore up the floor in the affected area. A plywood patch could be applied below the rotted area to act as backer for some rock hard floor patch.
Old 04-11-07, 08:02 AM
Thread Starter
Join Date: Jan 2007
Location: Long Island
Posts: 9
Thanks for the quick reply.
The leaks came from shower door frame where it was attached to the wall.
I'm redoing the bathroom so I'm going to eliminate the leaks.
As far as any other areas affected, I removed the shower pan, and all is well there. I have access to area from the basement, and as far as I can tell(poking with a screwdriver) the rot did not reach to the bottom of the subfloor or to the floor joists.
Old 05-04-07, 09:47 PM
Join Date: May 2007
Posts: 11
If just the top layer of ply is rotted, wire brush it, apply a fungicide, fill.
If the integrity of the wood is compromised, cut it out joist to joist, bridge w/hangers if necessary at any new seams, min 2x6DF2.

wood rot fungus is active at 14-20%, "germinates" at 28%.
Once moisture is removed, dormant(10-14%).

Wet wood doesn't rot,, like driftwood in a river.

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