NSR: Prepping for hardwood floors

[bagtagley]

I'm putting this here in the hopes of getting more traction than the Home Remodel thread. We're looking to put hardwood floors in the kitchen of a house we recently purchased. We've removed everything from the kitchen (including cabinets and appliances), and are ready to replace existing sheet vinyl floors. The original plan was to float engineered hardwood over the vinyl, but pre-finished hardwood doesn't cost much more, so now we're going that route. Next plan was to lay the hardwood on top of the vinyl, but there are enough issues with the floor (dips mostly), that I don't think that will be feasible.

Current plan is to pull the existing vinyl and 1/4" plywood and lay down prefinished hardwood. Subfloor is 5/8" T&G plywood, so I'd like to lay the hardwood directly on that (climberevan suggested against installing directly on any shimming, and said I should put a layer of ply over the patches/shims). Regardless, I'm still not sure how best to level out some dips in the floor. So far, nothing over 3/8", but I'll have to pull the existing vinyl/underlay to be sure. Most of the dips are against the walls, and the worst will be under cabinets and appliances. I have some 30# tar paper and old shingles I could use (according to the internet), but am concerned about smell and noise, particularly installing the flooring directly on top. Dap says their flexible floor patch can be nailed through, but that could get expensive and time consuming. I don't have ready access to door skins (internet suggestion), but am wondering if some of the wood-based underlayment options would work. I'd appreciate any expertise on this.

[s_curran]

We've done a few of these projects. Last one had glued down asbestos, so leveled that using asphalt paper, and thin plywood tapered with a belt sander. Anyone who's used to topography maps might even find this fun. We used a really straight piece of 10' board as our way of checking and marking. We then put the underlayment (wool like stuff, with a foil layer on top), and lastly the 1/2" pre finished bamboo nailed in on top.

You might want to reconsider removing the 1/4" ply, and take a look into that. Depending on your joist spacing, I think we sort of needed the 3/4" ply, plus the 1/2" ply. Plus I didnt want to make a ton of asbestos dust ripping that stuff up.

The first house we did, we used 3/4" pre finished hickory, so I wasnt as detailed as I was with the 1/2" bamboo which seems a bit more temperamental.

I'm not saying this is 100% correct, or even any percent, but it worked, and still has, without costing us a ton. For the first image, there is 1/4" ply wood under the parts that would have had more than 5 or 6 layers layers. Other wise, we found the tart paper can kind of bunch up once the install is started, which is a mess. This was a bit extreme overall I think, and it really got away from us while we were doing it.

[s_curran]

Reading your post a bit more, we installed the hickory directly over the tar and plywood one, but the one with asbestos and bamboo, we put that foil underlayment. They are both fine to us, but the underlayment does seem to help a bit with the thinner wood. We havent ever noticed a smell once the floors were installed over. If concerned, might be good to let it sit a bit before. Ours stunk up the house for a while while we were getting the floors installed and the sun hit the tar paper.

[Cocximus]

Lots G-flex epoxy.

[bagtagley]

Thanks, s_curran! That's what I was envisioning, but it's great it see an example. Just to clarify, when you say you put the hardwood directly on the tar and plywood, you mean plywood that was used for leveling, and not a whole new layer of plywood over the leveled surface?

[XXX-er]

floor leveling compound

but it also might be good to fix some of the structural issues causing the problem

[bagtagley]

Other than the DAP flex patch, I haven't found any floor leveling compound that you can drive nails through.

I'm open to fixing the floor from underneath. On visual inspection, I don't see any major issues with the joists, but I know there can still be sags and such. The biggest dip is into a wall. How do I fix something like that without being able to fully pull up the subfloor?

[oldirty]

I've used the 1/8" square vinyl tiles as shims to fill floor low spots. Not a huge fan of floor levelling products for hardwood, it's just too much work when you can just fill the spots with any building material that's strong enough.

Also, the home depot "red mat" tile decoupling mat works as nice floor levelling spacer, and so does a shitload of ramboard.

How do your elevations line up? Your pulling the vinyl (1/4?) And the underlayment ply. Is the floor your replacing it going to be the same height?

[bagtagley]

Yeah, the adjoining hallway is making that decision difficult. The kitchen floor is currently dead level with the hallway. Stacking hardwood on top puts me at least 3/4” higher. Probably closer to 1/4” if I pull the vinyl and underlay. What’s the acceptable limit before shit looks weird or Granny kills herself tripping into the kitchen?

I have time to pull the vinyl but dealing with the asbestos is giving me pause. It would only be me and a respirator and it’s sheet vinyl so I’d plan on pulling the ply with the vinyl attached.

[oldirty]

So higher is always easier than lower. The biggest issue if you floor is too low is the resulting gap between your doorframes and the floor. Since your going to be higher all you have to do is trim the door frames flush with the new floor before the flooring is installed.

3/4 is common. Many people drop a floor on top of existing floor, just need the appropriate transition piece. The only thing you need to check is will your existing doors open if the floor is 3/4 higher.

Have you looked into 1/2 or even 3/8 options?

[Shorty_J]

floor leveling compound

but it also might be good to fix some of the structural issues causing the problem

Floor leveling compound is very risky to use on a plywood floor. If you don't seal every crack first you get a mess downstairs.

I've used the topo map looking tar paper before under a maple floor and there is no smell once the wood is down.

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[bagtagley]

Have you looked into 1/2 or even 3/8 options?

No, and the wife is pretty set on the hickory we've already ordered. I'll present that as an option.

Maybe it's because it's forward progress and I don't love the idea of stacking on top of an old floor, but I really want to pull the old floor and underlayment. If it weren't for the potential for asbestos (house was built in 1979) and all that goes with that, I would already have done it.

Thanks Shorty_J, that's good to know.

[climberevan]

Asbestos is a hazard only if you pulverize it and breath it in for 8h/day for years. You're not going to be at any appreciable risk tearing up an old vinyl floor once with a mask on.

[climberevan]

The other question I'd look into is whether your sagging sections are just in the ply, or have whole joists sagged? This can happen at exterior walls when the roof load is big --it crushes the rim joist a little, while the next floor joist over stays higher. Topo-map shimming with whatever will be the answer here.

To answer your question from the other thread: if your current ply is sagging between joists, you can glue and screw new ply over it. Between the joists the screws will pull the old ply up tight to the new ply, nearly flattening the sandwich. You'll prob have to pre-drill the new ply to get the screws to pull the old stuff up. Alternatively (and preferably) you can put in new blocking underneath to push it up if you have access.

I also won't use self-leveling compound in most cases, and especially under nail-down (it just shatters). Plus it takes an unbelievable amount of it to really achieve anything. Years ago on one job I used like 30 bags and then pretty much swore it off.

[s_curran]

Thanks, s_curran! That's what I was envisioning, but it's great it see an example. Just to clarify, when you say you put the hardwood directly on the tar and plywood, you mean plywood that was used for leveling, and not a whole new layer of plywood over the leveled surface?

Yeah, you got it, no extra layers in between.

You'll like the hickory. We did the bargain basement ones from lumber liquidators, some had damage and numbers printed on them, lots of smaller pieces, etc. Super happy with it.

heres a photo of the finished space:

[bagtagley]

Alternatively (and preferably) you can put in new blocking underneath to push it up if you have access.

I do have access. How do I push the floor up with blocking?

[The Notorious J.O.N.G.]

Blocking is just pieces of 2x material spanning between joists. It’s a great way to go if your joists are on 24” centers and it’s actually the subfloor that’s sagging. You can also put them slightly higher than a low spot in the joist levels if you remove the subfloor. Do yourself a huge favor and get a cheap laser level, or build yourself a water level. It will be way faster and more accurate than using a long stick level.


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[bagtagley]

Thanks for the advice, you all helped me figure this shit out. There was some waviness that would have benefitted from shaving the joists, but the worst of it was what seemed like an intentional slope down to the entrance to the house. Sanding the ridge at the edge of that slope would have saved me a ton of time building up to the high spot, but we were committed to keeping the existing floor.

Not sure I can say I’m proud cause it’s just seems so wrong (I feel for the person that gets to deal with this mess in the future), but it did result in a nice, flat floor. Looking back, it might have have been quicker to pull the old floor cause flattening took forever, but I could also flatten in a fraction of the time with what I’ve learned.

Started with the big slope down to the door. Ran out of tiles pretty quick


So I moved to the middle


Back to the black hole


This was the dip I was originally worried about. Turned out to be pretty minor after spending a couple days on the other end.


And, done

[skuff]

Other than the DAP flex patch, I haven't found any floor leveling compound that you can drive nails through.

I'm open to fixing the floor from underneath. On visual inspection, I don't see any major issues with the joists, but I know there can still be sags and such. The biggest dip is into a wall. How do I fix something like that without being able to fully pull up the subfloor?

You can sister new floor joists to the old joists to help level your floor.