Layer Under Wood Flooring
I have a 4″ x 29″ hole in our hardwood floors – from where a plaster wall had been removed as part of a kitchen renovation. I did a not-very-elegant repair by resting a few pieces of wood on top of the wooden subfloor between the joists, and then placing a stained wood board flat on top of that – so the board is smooth with the rest of our hardwood floors. Here’s my question: Did I do something terribly wrong? Should I not have any weight on top of that wood subfloor beneath the joists? We’re on the third floor, and I don’t want someone’s foot coming crashing through the ceiling below! Or, is the subfloor strong enough to hold such a small repair? Thanks!
mharrisg
in Flooring 11 years ago
9
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9 replies
nalusurf | 11 years ago
It does appear that you are seeing a sub-floor underneath. What you did should be OK. You could cut a 2x and place perpendicular to the floor joists and screw in from the top to each joist, that would eliminate any bounce in the finish layer you put on top. Now, it would bother me that this cut is perpendicular to the direction of your flooring which is going to result in a patch job that will not blend with your finished floor simply because the run directions are perpendicular to one another. You could remove each cut piece back to where they originate and replace with the same flooring, but that is a much bigger job. Structurally you should be fine with your original plan, but the aesthetics are obviously up to you. Good luck!!.
mharrisg | 11 years ago
OK, I undid the repair to see what was under there – and what I said before was completely wrong. No joists. No lath. Funny how we create images in our head. It looks like there is a plywood layer underneath a few inches down. I took a picture so you can see (on the right side is some of the scrap wood I stuffed in the hole). And it looks like there are pieces of wood running perpendicular holding up the hardwood floor. My best guess is that the plywood can support weight, but I’m obviously no expert. From what you can see, do you think the plywood layer can support my repair (a layer of wood on top of the plywood, and then the hardwood board that’s even with the floor? Again, thanks – and sorry I got the details wrong before!
mharrisg | 11 years ago
Thanks everyone. I will try this out and come back to this thread if I have any questions. I appreciate your help!
Putnamdenizen | 11 years ago
What an extremely helpful thread. I hope it encourages other such inquiries and responses here!
nalusurf | 11 years ago
OK, mharrisg, glad you were able to clear that up. Here is what you can do: Open up the original repair, clear away any debris in the space between the floor joists. With a 29″ long opening as you state, you should easily be exposing the two floor joists (typically about a 16″ span between them). As DiBS pointed out you can “sister” some lumber along side each joist, instead of “blocking” as I had originally suggested as I think sistering would be easier. Old floor joists are usually around 8″ wide which would give you plenty of surface to sister a piece of 2×6 to each joist. You want to cut two pieces of a 2×6 so that they will extend beyond the width of your opening which is about 4″, correct? So, an 8″ long 2×6 should be plenty so that the ends extend beyond either side of the 4″ opening. Place each 2×6 along each joist (parallel) and such that the top is flush with the above sub floor. Use 3″ deck screws and secure each 2×6 with two screws to the joist. You now have sufficient nailing surface to cover the opening with a piece of subloor and then your finished flooring over that.
nalusurf | 11 years ago
DiBS, I see what you are saying but I think he is simply saying that his pieces of wood are between the joists but on top of the subfloor. Looking closer, my concern is that the OP says “wooden subfloor beneath” the joists, not between and resting wood “on top of that.” I really think the boards are resting on the ceiling below. Let’s hope OP replies and clarifies!!
mharrisg | 11 years ago
Yes, subfloor is the wrong term. Yes, there are wood strips – like you describe – lath. I didn’t see blobs of dried clay between them, but I did a Google search for lath – and that’s what it must be. So yes, I placed the pieces of wood on top of the lath, and then the finished piece of wood on top of that – with the weight bearing on the lath. Apparently, not a good idea. So, I guess I’ll reopen the repair and try to correct the problem. I’ll see if I can figure out how I can “sister” some 2x4s to the joists. Or maybe I’ll have to call a professional. Thanks!
daveinbedstuy | 11 years ago
Nalusurf, you misread. He did say “between” the joists. As long as the board that you laid down is fully supported by nailing it to joists, it will be fine. Or, as nalusurf said, “sister” some 2x4s to the length of the joists to further support the edge. You really should use 2x6s or 2x8s but if it is a very short span, 2x4s qill be adquate but would not meet code
nalusurf | 11 years ago
I’m having a bit of trouble picturing your repair and opening. When you say “wood subfloor beneath the joists” are you looking down at this repair from above? Just to note, sub-floors are NEVER below joists, they are installed on top of them. I think you are looking at the ceiling below. If this is correct, does this “subfloor” look like pieces of approx 1 1/2″ wide wood strips (called lath) that run perpendicular to the joists, and can you see what appear like blobs of dried clay between them (plaster keys)? If so, then you have a plaster ceiling below these joists. If not plaster, I am quite certain you are looking at the ceiling below. In any case, then NO, you should not have put anything directly on top of that “subfloor” between the joists. Lath and plaster are NOT designed to bear weight, nor is any finished ceiling for that matter. To repair this properly you should have installed what is a called “blocking” between the floor joists. That is a piece of framing wood cut to span between the joists (perpendicular) and level with the tops of the joists, and is then secured on either end to the joists. This would then allow you to place flooring on top of this area without placing any sort of weight on the ceiling below. I would recommend reopening your repair and correct this accordingly. It is not a difficult repair, but you may want to get someone who knows about this type of work to do it for you.