Sub Floor Replacement

[accolay]

To Replace or not replace.

I'm fairly close to deciding to replace a sub floor in an old house. Original floor is 100 year old tongue and groove 8" wide planks. Many are broken or cracked. Some probably have some rot. I've removed a few to replace wiring.

As far as I know, for the new flooring I'd need to attach another 1/2" subfloor. I could just fix what's there, but, then would still have to add more.

It's a relatively small space. I think I'm just going to have to do it.

[Papa bear]

What are you planning to install over top?


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[accolay]

I'm thinking wood laminate or vinyl planks

[lthenderson]

Depends on each case but I usually just put a new subfloor overtop the old one. Subfloors run underneath walls making them impossible to get out completely. It becomes a nightmare to deal with. Much easier to just put a new layer on top and deal with the loss of the thickness of the material to head space when it comes to doors and such.

[accolay]

I should have added that everything is ripped out down to the studs, including knee walls. I don't want to add more weight or height than I have to...pretty sure it's going to be ripped out.

[JustNeedsPaint]

If you are down to studs you are going all out. If you are going all out and finding a good number of broken and cracked planks, I'd error on the side of caution. Take it out and sleep peacefully. Now if you get down to replacing joists and beams...sigh. It might not be a merry Christmas present, but it'll be a happy new year for your house.

We replaced the subfloor (and floor joists) in the kitchen, bathroom and laundry room and put on the 1/2" plywood on top:
https://www.justneedspaint.com/hurricane-ike-bathroom-subfloor-repair/

[accolay]

Yes... like the layers of an onion this house... I've already replaced one footing and associated post in the basement, shoring up the rest of the beam with a 2x6 load bearing wall per engineering report. Also almost all of the 2x8 joists have been sistered since they were cracked, rotted, cut through, missing or rotting. The half story joists have to be sistered because.... one half of the house's joists aren't resting on the center load bearing wall.

At this point, I think it's easier to rip up the planks and replace the whole thing instead of piece meal replacement. It's going to be a real bitch getting that plywood up there by myself... maybe. I think lifting it up through the ceiling will be easiest.

[JustNeedsPaint]

You most definitely used some of the right choice words. ;-)

What do you mean by lifting up through the ceiling? Are you talking about replacing the subfloor under walls?

[accolay]

The ceiling on Floor 1 has been torn out (because at some point if you don't replace your roof, you'll eventually get water leaks that ruin plaster, among other things.) I figure the only way to get a full sheet of plywood up there anyway will be to lift through the ceiling of the first floor after removing a few more planks on the second because the stairs have two 90° turns, so I'm pretty sure they wont go up that way, or at least it sounds like it'd be easier to push up through the ceiling.

[JustNeedsPaint]

Ah, gotcha. I didn't realize this was on the second floor. Makes sense! Yet another bonus of having everything down to studs.

[Papa bear]

The ceiling on Floor 1 has been torn out (because at some point if you don't replace your roof, you'll eventually get water leaks that ruin plaster, among other things.) I figure the only way to get a full sheet of plywood up there anyway will be to lift through the ceiling of the first floor after removing a few more planks on the second because the stairs have two 90° turns, so I'm pretty sure they wont go up that way, or at least it sounds like it'd be easier to push up through the ceiling.

How do you expect to get drywall up there?

I would think you could get the plywood or drywall up there. Even 3/4 has some bend to it.

You know what this floor looks like more than us. Even a picture can't fully appreciate what is happening, but it could help with us giving recommendations.

As for repair can replace, I'm normally going with repair first. Cut out the bad part of the floor and square it off to hit at the mid point of a floor joist. At the ends without a joist, you can run a 2x4 block between the joists so that you can screw/nail/glue to something solid on all 4 sides.



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[accolay]

I'm usually a repair type of guy too. I looked at it again today. Probably 50% of these boards have significant cracks in them. I think in the end it'd be faster to replace the whole thing instead of replacing some of it, then adding another layer to install flooring on the planks.