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Old home subfloor - what would you do?

ZX3ST

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Jun 6, 2015
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Not garage related, but hoping the community might have some advice.

I have an old home I'm fixing up. It's obvious this home was built with scraps from another building.

Plank subfloor, which had been covered with 1/2" particle board and carpeted. The original subfloor has lots of gaps and is very uneven. A few high spots, but mostly it's low spots, weak boards in places, and gaps.

No matter what the particle board is getting ripped out. It's warped and swollen in many places. Luckily they didn't use ring shank nails so it's not THAT bad to tear out. I plan to put down vinyl plank as the finish.

I'm considering a couple options. I'm all ears if anyone can think of any alternatives.

1. Rip out old subfloor completely, and replace with new 3/4" T&G engineered subfloor. This would be a bit interesting since the floor joists are on 20" centers, which isn't great for sheet goods. This would however do me a favor on the transition into the addition, as it's currently 1/2" higher.

2. Put down 1/2" plywood over the existing planks and call it done. I'm concerned I'll have issues with the plywood settling into the dips of the planks over time.

How would you handle this? This isn't my forever home, but I also don't want to totally half-*** it. I can get more pics if that's helpful. Thanks in advance!



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The Cobbler

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I would leave the original sub floor in place.
find out if the highs are consistently high . if they are mark them and nail 5/8 over top running length ways with the original boards. cut shims to fill low boards if the highs are spaced far apart or your ply edge lands on a low board
 

Rusted Nut

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I’d recommend 5/8” or 3/4” T&G subfloor. Screw off the old planks before installing anything else. You could run a layer of 15lb tar paper or similar and pour 1/2” of Arden self leveling compound over the existing planks, then the T&G subfloor.
 
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tyyost

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Jan 14, 2009
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Tunkhannock, PA
I would definitely recommend 3/4 ply, shimming the lows is advisable as well. Anything thinner will quickly telegraph the current subfloor. What is the plan for the finish floor? Floating plank or adhesive planks?
 
OP
Z

ZX3ST

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STL
I would definitely recommend 3/4 ply, shimming the lows is advisable as well. Anything thinner will quickly telegraph the current subfloor. What is the plan for the finish floor? Floating plank or adhesive planks?
Floating vinyl plank with the preinstalled backer, such as Lifeproof, Smartcore Pro, etc.
 

tyyost

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Jan 14, 2009
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804
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Tunkhannock, PA
Floating vinyl plank with the preinstalled backer, such as Lifeproof, Smartcore Pro, etc.
I have been doing lifeproof in our bedrooms one by one. House had original 1/2 ply subfloor. I have been putting down 3/4 T&G ply down with construction adhesive and screws, did an Armstrong floating floor years ago and just did 5mm luan and eventually it conformed to the highs and lows of the joists.
 
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