Rotten Subfloor - Need Help

Ask your questions pertaining to the interior that don't fit in the above categories
JasonNewHouse
Posts: 22
Joined: Thu Apr 04, 2019 1:18 pm

Rotten Subfloor - Need Help

Post by JasonNewHouse » Thu Apr 04, 2019 1:41 pm

Hello everyone,

I just purchased my first home, built in 1927. I've ripped up the carpet and the existing floor in the living room and dining room to find out the sub-floor was all rotted. I went to Home Depot and purchased T&G Under-layment Plywood (Scant Face) (Common: 23/32 in. x 4 ft. x 8 ft.; Actual: 0.688 in. x 48 in. x 96 in.) and Loctite PL 400 10 fl. oz. Sub-floor and Deck Construction Adhesive. I also bought some 544 Floor Leveler 40 lb. Self- Leveling Underlayment for after the install. My goal is to lay some LVP throughout my whole house. I plan on ripping up the tile in the kitchen tomorrow and I know I will uncover more issues there. I have 0 experience with home improvements and need all of the help I can get.

I've attached a few pics and I also made a 20 second video.

https://youtu.be/YGhx8Z3sn1k
Attachments
Floor.JPG
Floor.JPG (4.09 MiB) Viewed 287 times
Floor 2.JPG
Floor 2.JPG (76.67 KiB) Viewed 287 times

User avatar
A. Spruce
Posts: 5716
Joined: Tue Aug 16, 2016 5:23 pm
Location: California, USA

Re: Rotten Subfloor - Need Help

Post by A. Spruce » Thu Apr 04, 2019 3:28 pm

What you have there is pretty typical of older home subfloor. Is there actual rot or just missing pieces of wood? if it's just missing pieces, I wouldn't worry about it and just sheet over it. If there is rot, then the bad sections of sub floor need to be replaced.

Depending on your area, you may also need a vapor barrier, which Shannon will have to weigh in on, as VBs are not common in my area.
If the women don't find you handsome, they should at least find you handy.

JasonNewHouse
Posts: 22
Joined: Thu Apr 04, 2019 1:18 pm

Re: Rotten Subfloor - Need Help

Post by JasonNewHouse » Thu Apr 04, 2019 5:16 pm

Hey Mr Spruce, thanks for the reply. My foot actually fell through the floor! I would only assume that its all rotted due to how brittle it is, and how nasty it looks, but I'm no expert. I was planning on pulling all of the floor up and just replacing it with the Plywood that I bought. Is that not a good solution? I'm in LA, CA.

User avatar
A. Spruce
Posts: 5716
Joined: Tue Aug 16, 2016 5:23 pm
Location: California, USA

Re: Rotten Subfloor - Need Help

Post by A. Spruce » Thu Apr 04, 2019 5:50 pm

Dry and brittle is vastly different from rotten. Rotten will be punky. Dry and brittle tends to look just fine, but can break out without warning, which is what the two holes in your picture look like to me.

Replacing the subfloor can be done, though, not without a lot of effort. The way homes are constructed, ALL the walls will be on top of the subfloor, making it difficult to change. I would recommend overlaying the subfloor with plywood, rather than trying to replace it. Also, it looks like your supports may be on 4' centers, which is well beyond anything that plywood can handle, which means to replace everything will require installing more support framing to carry the plywood. Lastly, because of this spacing, if you plan to install tile anywhere, you're going to need to beef up the support in that area to carry the weight of the tile and not flex. Flexing will cause grout and tile failure.

I'm in NorCal, when I retired VBs were not a requirement/necessity. It's been more than a few years since then, so that may have changed. I'd check with the local building department or local tradesmen on the necessity of a vapor barrier.
If the women don't find you handsome, they should at least find you handy.

JasonNewHouse
Posts: 22
Joined: Thu Apr 04, 2019 1:18 pm

Re: Rotten Subfloor - Need Help

Post by JasonNewHouse » Thu Apr 04, 2019 6:10 pm

Thanks, this is getting more and more scary for me. Have you seen my video? I have Luxury Vinyl Plank arriving tomorrow. Whats Punky mean?

JasonNewHouse
Posts: 22
Joined: Thu Apr 04, 2019 1:18 pm

Re: Rotten Subfloor - Need Help

Post by JasonNewHouse » Thu Apr 04, 2019 6:23 pm

I can only walk in certain areas and if I don't I am sure I'll fall through the floor again. I thought that replacing the whole subfloor would be my best bet, seeing that I would be eliminating this nasty wood.

User avatar
A. Spruce
Posts: 5716
Joined: Tue Aug 16, 2016 5:23 pm
Location: California, USA

Re: Rotten Subfloor - Need Help

Post by A. Spruce » Thu Apr 04, 2019 6:53 pm

Punky - spongy, sort of cork-like in texture and appearance.

I'm not saying you can't replace the subfloor, just that it's not as easy as peeling up a few boards and flopping down some plywood. It will be a huge project, especially if you have to add support framing because the joists are too far apart.
If the women don't find you handsome, they should at least find you handy.

JasonNewHouse
Posts: 22
Joined: Thu Apr 04, 2019 1:18 pm

Re: Rotten Subfloor - Need Help

Post by JasonNewHouse » Thu Apr 04, 2019 7:48 pm

It’s Punky

User avatar
Shannon
Posts: 12516
Joined: Fri Nov 25, 2011 11:58 pm
Location: Canada
Contact:

Re: Rotten Subfloor - Need Help

Post by Shannon » Thu Apr 04, 2019 8:25 pm

I agree with Spruce here , there really does not appear to be any actual rot just dry old lumber that can it times be “punky”😂.
It looks to me in the video that the joists are at about 24” o.c. so that is a nine issue.
I would simply lay the plywood right over the floor that is there . The plywood will span the gaps and cracks well and leave you with a solid floor again ready to install the vinyl plank flooring over. Btw no vapour barrier needed. Most likely the self leveled would not be needed either.

This will still be a job to tackle but much easier then removing all the old flooring.

You really do not need 3/4” t&g plywood either I think you could use 5/8” standard plywood which you simply butt together at the seams leaving just a small gap of maybe a 1/16” instead of trying to fit the T&G together as you go. If the joists are 4’ o.c then the T&G would be advised.

Place the sheets perpendicular to the floor joists if you can and end joints should meet over joists. Use the adhesive along joist line areas and use 2-1/2” to 3” long deck screws to secure the new plywood through the old wood floor and into the joists about every 12” apart in the main body of the sheet and every 6” to 8” along the end joints.
If you've found our videos or website information helpful, please considering making a donation using PayPal or pledging us on Patreon

JasonNewHouse
Posts: 22
Joined: Thu Apr 04, 2019 1:18 pm

Re: Rotten Subfloor - Need Help

Post by JasonNewHouse » Thu Apr 04, 2019 9:14 pm

Got it, I will not take this floor up then. Is it ok that I keep the plywood I have already purchased ? I don’t have a truck and would have to pay to take it back to Home Depot. As for install, the floor is currently uneven so that’s why I made the assumption to use the leveler, so how would it be level after laying the plywood on top ? Just to confirm, no vapor barrier needed in the crawspace ? It’s just dirt down there. I will try and measure the joists and give an update when I get home. My apologies for all the questions as I’ve never done anything like this before.

User avatar
A. Spruce
Posts: 5716
Joined: Tue Aug 16, 2016 5:23 pm
Location: California, USA

Re: Rotten Subfloor - Need Help

Post by A. Spruce » Thu Apr 04, 2019 9:39 pm

Yes, you can use the plywood you've already got. 3/4" plywood is going to span the dips and gaps of the existing subfloor just fine. You're probably not going to notice much for dips or lumps once the plywood is down.

I would also go to the effort of hammering down all the existing subfloor nails or replacing them with screws. If you don't do this, you will have squeaks that you won't be able to cure once covered with plywood. As Shannon stated, use screws long enough to get down into the floor joists. I'd use at least a 3" screw for getting down into the joists.
If the women don't find you handsome, they should at least find you handy.

JasonNewHouse
Posts: 22
Joined: Thu Apr 04, 2019 1:18 pm

Re: Rotten Subfloor - Need Help

Post by JasonNewHouse » Thu Apr 04, 2019 9:56 pm

Ok,

Do I rent a nail gun? Do I use both glue and nails? What size nails to use on the existing subfloor?

P.S. I will upload another pic that shows some patch work done that looks pretty suspect.

User avatar
A. Spruce
Posts: 5716
Joined: Tue Aug 16, 2016 5:23 pm
Location: California, USA

Re: Rotten Subfloor - Need Help

Post by A. Spruce » Thu Apr 04, 2019 10:22 pm

Nails don't hold as well as screws. Use structural screws, not drywall screws. Glue helps prevent squeaks, as does 1/16"-1/8" seam gaps on the plywood.

If you've got rotten subfloor, you will need to replace those pieces before covering with plywood. The new material needs to be the same thickness as the old, so you may need to use shims or have custom milled lumber made for the patches.
If the women don't find you handsome, they should at least find you handy.

JasonNewHouse
Posts: 22
Joined: Thu Apr 04, 2019 1:18 pm

Re: Rotten Subfloor - Need Help

Post by JasonNewHouse » Thu Apr 04, 2019 10:53 pm

Please see the pic of another part of the floor, this is in the dining room, and another reason why I wanted to tear the whole floor up.
Attachments
BB1E9D76-C301-4386-AC36-5A1BDDEC2D29.jpeg
BB1E9D76-C301-4386-AC36-5A1BDDEC2D29.jpeg (2.86 MiB) Viewed 263 times

User avatar
A. Spruce
Posts: 5716
Joined: Tue Aug 16, 2016 5:23 pm
Location: California, USA

Re: Rotten Subfloor - Need Help

Post by A. Spruce » Thu Apr 04, 2019 11:24 pm

Not sure what you're showing us.
If the women don't find you handsome, they should at least find you handy.

JasonNewHouse
Posts: 22
Joined: Thu Apr 04, 2019 1:18 pm

Re: Rotten Subfloor - Need Help

Post by JasonNewHouse » Thu Apr 04, 2019 11:49 pm

Sorry for the low lighting, I was showing another part of the floor that had some sort of patch work done.

User avatar
A. Spruce
Posts: 5716
Joined: Tue Aug 16, 2016 5:23 pm
Location: California, USA

Re: Rotten Subfloor - Need Help

Post by A. Spruce » Fri Apr 05, 2019 12:00 am

is that just nailed over the top of the subfloor or was it mortised in for some reason?

If over the top, rip it off, repair subfloor as necessary and cover with plywood. If mortised in, pull it up and repair damage before sheeting.
If the women don't find you handsome, they should at least find you handy.

User avatar
Shannon
Posts: 12516
Joined: Fri Nov 25, 2011 11:58 pm
Location: Canada
Contact:

Re: Rotten Subfloor - Need Help

Post by Shannon » Fri Apr 05, 2019 8:57 am

JasonNewHouse wrote:
Thu Apr 04, 2019 9:14 pm
Got it, I will not take this floor up then. Is it ok that I keep the plywood I have already purchased ? I don’t have a truck and would have to pay to take it back to Home Depot. As for install, the floor is currently uneven so that’s why I made the assumption to use the leveler, so how would it be level after laying the plywood on top ? Just to confirm, no vapor barrier needed in the crawspace ? It’s just dirt down there. I will try and measure the joists and give an update when I get home. My apologies for all the questions as I’ve never done anything like this before.
You can use that plywood for sure ,as it seems it would cost you more to return it then you would save.
As far as the "levelness" of the floor ...you really likely do not need it level but you do need it reasonably "flat" or "true" for the flooring install. The flooring you use should have a recommendation of how "true" the surface needs to be .Something likely like no more then a 3/8" difference in a 4' distance?

As for vapour barrier, you could add it under the plywood but this will prevent you from being able to use the construction adhesive to help hold the plywood down and prevent squeaks. In most areas it is recommended to use a black heavy poly layer on the dirt in the crawl space to control moisture. Over lap the joints a couple of feet and run it up the foundation a foot or so and seal it to the wall.
If you've found our videos or website information helpful, please considering making a donation using PayPal or pledging us on Patreon

User avatar
Shannon
Posts: 12516
Joined: Fri Nov 25, 2011 11:58 pm
Location: Canada
Contact:

Re: Rotten Subfloor - Need Help

Post by Shannon » Fri Apr 05, 2019 9:00 am

A. Spruce wrote:
Thu Apr 04, 2019 9:39 pm
Yes, you can use the plywood you've already got. 3/4" plywood is going to span the dips and gaps of the existing subfloor just fine. You're probably not going to notice much for dips or lumps once the plywood is down.

I would also go to the effort of hammering down all the existing subfloor nails or replacing them with screws. If you don't do this, you will have squeaks that you won't be able to cure once covered with plywood. As Shannon stated, use screws long enough to get down into the floor joists. I'd use at least a 3" screw for getting down into the joists.
Great point about securing all the old planks before starting.

I would also suggest taking a look for any wiring or plumbing passing through the joists near the top couple of inches to be sure you don't puncture anything.
If you've found our videos or website information helpful, please considering making a donation using PayPal or pledging us on Patreon

JasonNewHouse
Posts: 22
Joined: Thu Apr 04, 2019 1:18 pm

Re: Rotten Subfloor - Need Help

Post by JasonNewHouse » Fri Apr 05, 2019 12:56 pm

All attachments are self explanatory. Does this provide more info?
Attachments
65F38E2E-DF22-482A-A6D6-E2DF0B997E94.jpeg
65F38E2E-DF22-482A-A6D6-E2DF0B997E94.jpeg (2.07 MiB) Viewed 227 times
18FA5127-7CA3-4D2F-963E-CEF2320AF145.jpeg
18FA5127-7CA3-4D2F-963E-CEF2320AF145.jpeg (2.89 MiB) Viewed 227 times
AB3699C2-54CA-4AEE-88C3-C23C6447BA60.jpeg
AB3699C2-54CA-4AEE-88C3-C23C6447BA60.jpeg (2.12 MiB) Viewed 227 times
F0D83074-DF1A-4AAF-9B36-BD0938BCD3DA.jpeg
F0D83074-DF1A-4AAF-9B36-BD0938BCD3DA.jpeg (3.07 MiB) Viewed 227 times

User avatar
Shannon
Posts: 12516
Joined: Fri Nov 25, 2011 11:58 pm
Location: Canada
Contact:

Re: Rotten Subfloor - Need Help

Post by Shannon » Fri Apr 05, 2019 11:00 pm

So you have some un flatness but it does not look that bad and the plywood will span much of it and even things out.

Really can’t tell from picture how far apart joists are you can measure those easy enough.

Looks like there is some plastic covering some of the dirt but should cover all of it.
If you've found our videos or website information helpful, please considering making a donation using PayPal or pledging us on Patreon

JasonNewHouse
Posts: 22
Joined: Thu Apr 04, 2019 1:18 pm

Re: Rotten Subfloor - Need Help

Post by JasonNewHouse » Mon Apr 22, 2019 6:46 pm

Help!

Since this 3/4th inch floor I have isn’t designed to lay on existing subfloor should I take it back and get 1/2 inch plywood?

User avatar
Shannon
Posts: 12516
Joined: Fri Nov 25, 2011 11:58 pm
Location: Canada
Contact:

Re: Rotten Subfloor - Need Help

Post by Shannon » Mon Apr 22, 2019 8:42 pm

The 3/4" is fine ,its just a bit of over kill. But if its going to cost you again to have it taken back i would just use it .
If you've found our videos or website information helpful, please considering making a donation using PayPal or pledging us on Patreon

JasonNewHouse
Posts: 22
Joined: Thu Apr 04, 2019 1:18 pm

Re: Rotten Subfloor - Need Help

Post by JasonNewHouse » Thu Apr 25, 2019 12:16 am

It won’t cost me to take it back. I just want to get it right the first time.

User avatar
Shannon
Posts: 12516
Joined: Fri Nov 25, 2011 11:58 pm
Location: Canada
Contact:

Re: Rotten Subfloor - Need Help

Post by Shannon » Thu Apr 25, 2019 8:16 pm

No real right or wrong here. If your floor now is weak and spongy then the 3/4" would make it nice and study again. If the existing floor is pretty solid then 1/2" or 5/8" would do the trick.
If you've found our videos or website information helpful, please considering making a donation using PayPal or pledging us on Patreon

JasonNewHouse
Posts: 22
Joined: Thu Apr 04, 2019 1:18 pm

Re: Rotten Subfloor - Need Help

Post by JasonNewHouse » Wed May 01, 2019 2:50 pm

Thanks, I ended up using 1/2 inch sheathing plywood from Home Depot.

JasonNewHouse
Posts: 22
Joined: Thu Apr 04, 2019 1:18 pm

Re: Rotten Subfloor - Need Help

Post by JasonNewHouse » Wed May 01, 2019 3:04 pm

However I was worried that this plywood wasn't designed for underlayment purposes.

User avatar
A. Spruce
Posts: 5716
Joined: Tue Aug 16, 2016 5:23 pm
Location: California, USA

Re: Rotten Subfloor - Need Help

Post by A. Spruce » Wed May 01, 2019 6:19 pm

It depends on what you're doing what kind of underlayment or layers of underlayment you'll need. Because your subfloor is so uneven, you need a layer of plywood, aka underlayment, to even that out, this is good enough for carpet and probably most wood floor installations. If you were to lay tile or vinyl, then you need an even smoother surface to work from, so another layer of underlayment will probably be necessary. Again, it just depends on the needs of the flooring that you are installing.
If the women don't find you handsome, they should at least find you handy.

JasonNewHouse
Posts: 22
Joined: Thu Apr 04, 2019 1:18 pm

Re: Rotten Subfloor - Need Help

Post by JasonNewHouse » Wed May 01, 2019 6:26 pm

Installing Luxury Vinyl Plank on top of the 1/2 inch plywood

User avatar
A. Spruce
Posts: 5716
Joined: Tue Aug 16, 2016 5:23 pm
Location: California, USA

Re: Rotten Subfloor - Need Help

Post by A. Spruce » Wed May 01, 2019 7:05 pm

I'm not familiar with vinyl plank, so Shannon will have to advise. In preparation for that, what is the surface like, i.e., smooth, rough, irregular? A pic or two will help Shannon help you. Why is this an issue, because VP may not have the ability to absorb or span irregularities, resulting in those irregularities being telegraphed through the VP.
If the women don't find you handsome, they should at least find you handy.

Post Reply