Hello All,
I’m getting ready to install 3/4″ thick hardwood floors in my house and have a question regarding subfloor leveling that I hope someone can shed some light on for me. My original subfloor consists of tongue and groove 2×6’s and the problem is that over the years the foundation has slightly settled and the subfloor boards aren’t perfectly level anymore. I’d say that at the worst spots the height difference between the boards is about 3/8″ which occurs at the exterior perimeter walls, and the worse spots throughout the main interior of the house are about 1/8″.
My question is; do I need to use some type of floor leveling compound to level out the subfloor imperfections? Or do I need to use wood shims to “fill” low spots? Or can the 3/4″ thick boards “float” over the imperfections? I want to do this right and I want to try and avoid future floor squeaks and creaks as much as possible. Anyone have any advise?
Replies
Depends whether the 3/8" change happens over two feet or twelve feet.
if the latter, ignore it. if the former use cedar shim shingles.
1/8" in 2-3" feet is fine.
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Do not use a leveling compound. It will crack and deteriorate over time.
Do, scew the existing sub floor, if you want to be fussy, a beltsander will knock down some of the high points, like a badly cupped piece of subfloor.
Another option, skin existing subfloor with 1/2" ply, glue and shoot to joists. This, of course, raises the floor elevation. Not really desireable in most situations, but if you happen to be doing ceramic or stone elsewhere, it might be beneficial.
If your 3/8" deflection is over 2' or less, you could skin the floor with 3/8" ply. This option is a tough call. Only because you have to make sure you're not createing another problem in terms of level, somewhere else.
Sanding the high part of the subfloor and the finish floor can help as well, although, you can only reduce the slope by maybe 5/16ths.
Ya gotta love workin' on them old houses.
Adding a layer of plywood is not going to do anything to level the floor. If you screw the new layer to every joist like you should, then the ply will simpoly conform to the topography. And you run the risk of not installing a suitable subfloor material ... not all plywood is rated for under wood flooring.
Shims cut from tarpaper will work for shallow depressions, and shims ripped from ply will work for deeper ones.
I cannot imagine trying to sand down a large area by 5/16 of an inch. If it is a small bump that might work. But then you are reducing the subfloor thickness by more than 1/3."Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
Let me clarify a few points, I haven't explained my thoughts very well.
I have skinned several floors with plywood sheathing. Usually for either 2 reasons, to match an elevation at an adjoining room or to stiffen and "float out " an existing subfloor. On one house, the existing subfloor was badly cupped. I used the beltsander to knock down the high edges of the 1x5 t&g sub. (a real floor sander would have been ideal but I didn't have one) then placed adhesive on the floor, making sure to have good coverage in the low part of the cup (liquid shims) shoot carefully to joists. The final result was a reasonably flat floor that was rock solid.
"Skinning with 3/8" Yea, I definitely did not explain this well.
Again, one house, 100 yrs. old, large rectangular rm. Three walls on perimeter foundation, forth long wall on a beam. The whole floor was "dished". From the perimeter out into the room, in about 2', the floor dropped approx. 3/4". The center of the room had a deflection of about 1/2". So, as a quick fix, we skinned the center of the room with 3/4" ply. Cut shims from approx. 3/4" to nothing, left the 1/2" deflection in the center, and laid hardwood. It wasn't perfect, but it was fast and really looked good.
"picking up 5/16" With a cheap planer and beltsander, I've knocked down some high sections of a subfloor, as much as 3/16" and a fair amount of square footage. when it comes time to sand the hardwood, pre-sand the high areas, then do a final sand on the entire floor. Yes, you do lose life on the floor, (god help the next guy who has to sand)
I've also removed subfloors and sistered, leveled and new ply, but sometimes the homeowners just don't have the money. I've had to get creative when working in wonky old houses, but, honestly all these options have worked well and its work that can be done by anyone with a little patience.
we skinned the center of the room with 3/4" ply. Cut shims from approx. 3/4" to nothing,
That part makes sense."Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
dminiken
Ask yourself do you really hate not having perfectly flat floors? I don't, charcter is far more important to me than machine like perfection.. in fact I decided that would deliberatly add character into my house. I'm hoping that my floors squeek and creek as I walk alcross them because I remember that sound in my grandmothers home..
I grew up in those souless places where tract homes exist. Every third house was a copy. The yards were all 150'x150' the three bedroom rambler with attached garage nice flat floors that were quiet and plain.. sheetrocked walls and ranch trim the only variation was what color pastel did you paint the rooms.
Maybe that sounds good to you, but I want differant.
You didn't mention how old the house was or why you felt the foundation "settled".
I'm admittedly pretty picky about this sort of thing and would likely seek out the root cause and fix that rather than sanding or shimming the subfloor. Of course, that's easy for me to say given that the solution might well lead to new foundation work and jacking up a house, which leads to cracked walls, etc.............
Nevermind.
This is why inevitably the smallest project in my house leads to a total room and/or floor remodel.