Rotting subflooring


Old 12-07-04, 05:00 PM
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Unhappy Rotting subflooring

I am in search of some help. I own a three level end unit townhouse. I am replacing the floor in my living room (which is the middle floor of the house). When I got to the point of removing the existing flooring in my entry way (stick tile linoleum, then underlayment, vinyl linoelum sheet, then underlayment) I came to the subflooring. The subflooring is rotting apparently from water damage directly below where the door trim ends ( on each side of the door). I know the reason this occurred is because no one ever insulated the door frame behind the trim nor the base of the trim since I can feel air coming in--I am correcting that problem with The Non-Expanding Great Stuff designed for Doors and Windows.
The rotting section is a small section--I was planning to cut out a 12"x12" section to fix each side. My concern is this is the subflooring right at the door--what do I use to cut it? How do I cut it without comprimising the door frame and causing it to go un-plumb or falling askew on the bottom of the metal door frame that meets the subflooring? I know I need to cut the depth of the subflooring (which I believe is 5/8") or less to avoid cutting the floor joists. Are screws better to use than nails for the replacement subflooring? I was told to sand the edges of the new to the old where it butts up to make it a smoother floor--is this correct?
I will be grateful for any help. I am a first time homeowner and all the projects I've taken on have been fine--overwhelming at first, but fine. This one worries me. Anyway thanks for any suggestions.
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Old 12-07-04, 11:06 PM
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The foam is good for stopping drafts, but you need to waterproof the door opening, (behind the jambs) to keep the water from getting in. And keep in mind water is a weird thing once it gets inside a structure, it may run along a joist or stud for some way before it appears as a leak.

A skill saw is what I'd use to cut out the damaged subflooring. Just set the blade depth so it doesn't cut into the joist like you mentioned. The door unit (should) be anchored well enough that it won't come out of plumb when you remove the damaged sheeting that's under its edge, but no promises there. You may end up rehanging the door. Just depends on the extent of the damage & how well things were put together originally.

Definitely screws are better than nails, and glued & screwed is even better & the way I recommend to do things. Make sure to use the same thinkness of sheeting for the repair. From the sounds of the demo description, I'd say you're going to add at least one more layer of subflooring over the repair to get you finish floor height to come out right, so don't think to much sanding at the repair will be needed, just level & smooth it off is all.

HTH, post back if you've still got questions.
Old 12-08-04, 10:24 PM
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Thanks for your help. Just one dumb question, what do I use the glue for--to glue the back of the subflooring down or in the screw holes?
Old 12-10-04, 02:05 AM
Join Date: Dec 1999
Location: Northeastern NC On The Albemarle Sound
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The subfloor is probably 3/4" and underlayment would be 5/8". Joists should be on 16" centers (14.5" space between).
Cut the bad flooring out back to the centerline of the nearest good floor joists, so that you have something solid to screw the new flooring to.
Install 14.5" 2X cross-bracing between the floor joists (with angled screws in pilot holes), half under the old subfloor and half under the new for the same reason.
Use safety glasses and a circular saw with an old blade (you WILL hit nails) adjusted to the depth of the flooring level that you're cutting, as discussed. Pry the bad pieces out with crowbar, flatbar and clawhammer.
Use glue or Liquid Nails (caulking gun) on top of the joists before screwing the new flooring piece(s) down.
Good luck!

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