leveling slightly wavy planks

[jms]

*edited to change "level" to "flatten"


Hi, I'm about to dive into my floor replacement. We currently have carpet over the top of planks, which I believe are pine. The joists are not accessible from below. I am planning to pull the carpet and put down 5/8" plywood, and then put some pretty rigid vinyl planks that have pads already glued onto them on top.

So, I have two main questions:
- The planks have some slight unevenness - maybe 1/8" over a couple of feet. There are a few places that need a little more than that. How do I flatten the planks before putting down the plywood? Should I shim it with shingles and felt? I don't want to use any SLC, and I'm not sure any patch compounds would adhere to the planks very well. Just ignore it and throw the plywood down over the top?
- How should I fasten the plywood to the planks? I know I should not fasten the plywood to the joists through the planks. Which makes more sense - screw or nail? My main question here that nobody seems to mention is what fastener pattern to use in this situation. Just pretend I'm fastening to joists, but offset by a few inches?

Thanks!
John

 

[Ernesto]

Staple down layers/sheets of roofing felt. Your usually allowed 1/8 in in 3 ft on click vinyl plank.

 

[Nick]

Depending on how deep the valleys are in between the joist I use a roofing shingle , then 30lb felt to 15 lb then rosin paper to feather it out .

I've had some where i had to use two layers off shingles to get it up to where it should be .

 

[Incognito]

I rarely encounter such challenges doing commercial installations. I've used the methods above a couple times-----layering felt and such to flatten out the substrate.

For the plywood fastening you're going to want to 4"-6" between staples/nails in the field (the main portion of the sheet) and 2" apart along the seams-----staggered. So along all the seams there's a fastener every inch but they're not aligned with each other.

If you have a compressor and staple gun that's the way to go for DAMN sure. If not depending on the size of the area use ring shank nails with the same fastening schedule. Whatever size staples/nails you use should not penetrate through the subflooring. So make sure they are a fraction of an inch shy of that. You could probably get away with screws of some sort but I guaranty you that will be a big PIA.

To you and the others that responded--------what about a belt sander? Seems like you might be dealing with a handful of curled boards that could be more easily buzzed DOWN as opposed to raising up the lower areas with shimming materials.

 

[Ernesto]

I rarely encounter such challenges doing commercial installations. I've used the methods above a couple times-----layering felt and such to flatten out the substrate.


To you and the others that responded--------what about a belt sander? Seems like you might be dealing with a handful of curled boards that could be more easily buzzed DOWN as opposed to raising up the lower areas with shimming materials.

Sounds like 1 x 6 fir subfloor. I doubt a belt sander would make a dent.
I never run into those out here so i yield to Nick the ruling authority here.

 

[Floorist]

I haven't seen one of those here for years either. All the old buildings here have oak subfloor. Oak is plentiful around here, always has been.