I want to lay 3/4″ Jatoba T&G hardwood on a floor that comprises 5/8″ T&G plywood on 2″ x 10″ joists on 16″ CRS. The house is nearly 30 years old and the floor is dry and sound except that the plywood sags between 1/16″ and 1/8″ between the joists.
I’m contemplating laying the hardwood perpendicular to the joists and nailing over the joists. Will this be satisfactory? Thanks for your thoughts.
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Replies
If a wavey floor that will probably start splitting off the tongues or the top of the grooves is ok, then it's satisfactory. Otherwise, I wouldn't lay good flooring over a bad subfloor.
i don't see this working. if you have staggerd joints ,some of those joints are going to fall on the "low" part of the floor. so when you nail there it is going to suck down to subfloor,then the next one trys to bridge over. you might look at a pourable type floor leveler. larry
hand me the chainsaw, i need to trim the casing just a hair.
Thanks for your comments - I had a feeling this was going to be the case. I was hoping to avoid the time and mess of applying a leveling compound, but maybe there's no way out.
I don't see leveling compound as an answer either. Whatever is wrong with the ply - other than being only 5/8" it can still be wrong and continue sagging lateror at least cause squeaks.
I would do one of the following - replace it all with 3/4" T&G ply or advantec
or add an underlayment 1/2" with glue and screws or ring shanks to what is there now to straighten and strengthen
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I agree with Piffin that replacing with good 3/4" t&g would be ideal. However, unless your house is balloon framed, the 5/8" goes under the exterior walls and is an integral part of the structure.
If you keep the saggy plywood, you should put a thin layer of self-leveling compound followed by the layer of 1/2" plywood. Just placing 1/2" ply over the waves will lead to more squeaks as the top layer flexes up and down.
5/8" seems thin, but it is done a lot and I've never seen sags like you describe. Is the face grain perpendicular to the joists? Defective plywood? Seems weird to me, is all.
Bill
I agree. I have never used 5/8" myself, but have neve seen such sags in it before either, so I have to assume there is something going on here. Maybe house was left open too long in weather or maybe there is moisture problem from under it....As to gap filling - the leveling comppound in this case might be fine.I use polyurethene glue though which is moderately self expanding when curing, so that helps to do gap filling - you just have to use a boatload of it.
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Yeah, I knew you were a PL Premium kind of guy like me. After I posted I reread your post and had that same thought, that a boatload of PL could bridge those valleys and get the two layers working together. Maybe the pressurized gun attached to the 55 gallon drum.Bill
The house was definitely "built to a budget", hence the 5/8" ply, but it's built on rock and the crawlspace is always bone-dry. I doubt that it's still moving, but would guess that it got very wet during construction.
The room in question sees only light use. Tearing up the subfloor would be somewhat heroic, and laying 3/4" on top would be a good, but heavy-duty, solution. On the other hand, screwing down something like 1/2" will surely deflect to conform to the 5/8" below. Sounds like using a leveling compound to fill the sags is the way to go, and it probably doesn't have to be perfect - it just has to support the hardwood mid-span.
You need to be aware that, if you use a cementitious floor leveler (the standard "self-leveling material") it will probably shatter every place you drive a nail. That will lead to the sound of crunchies every time you walk in that area.
I did some work in a 1924 house that had oak flooring laid directly over the joists with no plywood, so your original idea of just laying the new floor perp to the joists is not unusual.
"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
If your subfloor is already sagging how is pouring concrete on it going to help anything?
Run a circular saw down your walls leaving some sticking out from the bottom plate, screw blocking in at the seam so that the new and old subfloor split on the blocking.
On walls parrallel to the joists cut the subfloor down the middle of the joist.
Then lay your new 3/4 t&G subfloor.
Yeah, the result will be about same as taking a few sheets of shattered glass to scatter around abnd then trying to run flooring over it all.
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OK, so the issue is whether there will be problems laying T&G hardwood across the joists. Some think that the flexure between the joists will cause the tongues and grooves to break where the subfloor is sagging and doesn't provide enough support; others think that that this isn't a problem because the subfloor is superfluous. Does anyone have a definitive answer on this?
The suggestion of butting the boards over a joist might help if the flooring, which is pre-finished, has plain ends. I don't know whether this is the case or whether they have micro-bevels. On the other hand, maybe the tongues and grooves will split just the same.
I can certainly imagine a leveling compound fracturing under impact. Maybe it just needs some strips of closed cell foam to help spread the load...
You would be OK if all the joints in the flooring spliced on a joist. In reality, very few will. Those that splice over the sag are the ones that will break. Also, those that are nailed in the sag will tend to get pulled down and squeaks are guaranteed.
Think a bit more about ripping out the old plywood, and replacing it with new 3/4" ply or advantech. Basically, set your circular saw to 5/8" depth with an old blade, cut all around the perimiter of the room, and maybe down a few of the joist bays. Before you do this, check the crawl space for any wires/pipe close to the subfloor.
Take a wrecking bar, and pull up all the plywood. Hope that it isn't glued and screwed down, like you're going to do with the new one. Cut solid blocking and screw it in place around the edge of the room. lay down some new subfloor, glued with PL premium, and screwed or ring shank nailed down. Shim up the perimiter of old subfloor with 1/8" doorskin glued down.
It's a better solution than ignoring the problem, or than using self leveling compound. Piffin's method will work, but I'd avoid adding 1/2" of floor thickness if I could just do this. On my house, anyway.
Cheers,zak
"When we build, let us think that we build forever. Let it not be for present delight nor for present use alone." --John Ruskin
"so it goes"
I know this is the right way to do it, but the house was not well designed nor was it well built in the first place. I already spend all my spare time fixing other folk's work and there comes a time when I have to accept that I can't make a silk purse out of a sow's ear. Although the house is worth too much to knock down and start again, a future owner may think differently given that in recent years the lot has appreciated to around four times the value of the house.
So although I generally prefer to do things properly, in this instance an "adequate" job will do (if I can figure out what it is)...
Martyn,What about installing diamond lath stapled down well and self-leveling compound over that? Once it cures lay yourself an engineered hardwood floor, either glued or floating. If you tighten up the subfloor with screws first, this could solve your problems pretty easily, and it would be nice and quiet. Of course, this will only be simple if the floor is basically level to begin with.You could also lay cork or real parquet squares once the compound dries out. Or tile. It gives you lots of options while flattening/stiffening your floor.Bill
Hey bill,
when reading all of all the posts in this thread yours seems to make the most sense to me.
I am a high end builder w/15 yrs in, and i can say that your idea will work if done properly and if you don't mind the messy "green snot" glue. I live in the philadelphia suburbs so the occasional city job has become the norm. I just recently put a glue down hardwood over leveler and it worked great,(used adhesion promoter, poured all @ once, etc.) but this was on the 15th floor kitchen of a high rise (masonry over masonry) I don't know if the wood flex of the subfloor would do to it but I've had no complaints and lots of praise on that one.
Less work, same end result.
If the joists are properly sized and spaced correctly and you can live with some additional floor height I would consider the following: Using the proper sized notched trowel apply a layer of thinset over the entire area. I think unmodified would be best. Before it sets place 1/2 inch exterior grade ply over the area. Use industry standard layout practices for the plywood install. Screw with correct fasteners in a six inch grid pattern. Allow to set over night. You now will have a flat surface to install your hardwood over. The thinset and ply will have leveled your floor. It concerns me that you have the 5/8 sagging condition. The cause of that should be determined before doing the above.
Tearing out the 5/8 is a good option also as long as it will come out without needing dynamite!!!!!!!
JMO
Thanks for all your ideas, guys. I'm reluctant to add further to the floor height - I've already furred the ceiling by 1 1/2" to accommodate radiant heating. I should have mentioned that the sagging isn't uniform across all the joist bays - some show little or no sagging while others show up to 1/8" - thus it might be feasible to contrive for the butts in the hardwood to fall over the joists in the worst areas. Perhaps a polymeric leveler rather than a cementitious one would be the answer, if there is such a thing...
Martyn,Re: polymeric leveler. You can hand float the subfloor dips with epoxy thickened with microballoons. (It is called #407 low-density filler when bought from Gougeon Bros.) This is a low density fairing compound that is easy to nail through because the filler consists of tiny hollow spheres. I have used this with great success in a variety of applications. The epoxy will stick very well to the plywood, and the flooring will sit flat and can be nailed without fracturing the fairing compound. This is used on boats to create true curves that look "fair" to the eye, hence the name. It sands easily when cured, but wear a mask for the dust.You have now gotten a number of good options to consider. Do report back what you decided to do and how it went. Best of luck.Bill
Holy Crap
I'm wondering if I'm being put on here...............
After 25 years and probably 200 jobs like what your describing, I'm here to tell ya, it's really no big deal. A sixteenth to an eighth of "sag" in 16" ? BFD!!! Look at ANY floor that old and see if the ply doesn't sag that much ( or more ) under the underlayment & rug! Cut the ply at the wall and put in BLOCKING to receive the new ply??? Are you kidding? Crap work!! Floor leveler? My diastolic just went up 50 points.....
Do the oak perpendicular to the joists ( which is the only right way anyhow) and don't sweat it. The tongue & groove won't split because of the (low) plywood. Try putting a few rows together WITHOUT ANY ply under it and support it at 2 ft o.c. , and I'll put $ that you won't be able to split ONE of them jumping up and down on it..You don't need to worry about ending the seams at the joists, either, since it's random length and therefore impossible, but try to stagger your joints so there aren't two in subsequent rows in the same joist bay.....
There are a lot of smart people here, well worth listening to, and some have posted in this thread, but sometimes you have to say WTF..............................
Bing
Are you for real?You sound like the kind of guy where people hire me two years after you are done to redo it again
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I will preface this by saying that generally I respect your opinion and input on this site.......
Yes, I'm for real, and good luck finding someone that I've had a callback from in the last 25 years. I'm sorry I'm not some 20 year old who is intimidated by the holy ones on this site. Everything I posted is true, backed up by a whole lot of time in this business. 5/8 ply was the industry standard in this area for a long, long time ( no, not by the hacks, actually by the guys who G a S) In fact, it was the hacks who started using 3/4 so they could save $ on underlayment and put rug right over the subfloor. I just find it difficult to fathom the hubbub created by such a minor defect in a substrate that will amount to no difference at all in finished product. If the ply were damaged or de-laminated, beat up, or sagging more than the op had said, or if it were 24" oc. I might entertain the thought of a solution. However, 1/16 or 1/8 inch of "sagging" is negligible and to be expected.
my .02
Bing
Once again my sincere thanks for all your helpful comments and suggestions. Since I now have plenty of ideas and also because it wasn't my intention to provoke any contentious arguments, let's call a time-out here.
Here's what I'm going to try: first I'll survey the floor to identify the best and worst areas. Then I'll lay the hardwood perpendicular to the joists as already stated and will pay attention to keeping the butts away from the worst areas. I'll "shim" the low points with a firm material such as felt or foam sill gasket to add some further support. I'll nail every board over each joist, although I haven't yet decided to what extent I'll nail between the joists. I would guess that nailing every 16" is probably sufficient anyway, but I'll check. This might sound to some like a quick-and-dirty solution, but it's easy to try and I think it has a good chance of working in this low-traffic room.
Finally, I will report back, not least because you've all given me a far better response than I ever expected, although it might take me a couple of months because this is a spare time renovation that has to take its place among my other family responsibilities (and it's been running for two years already). Thanks again for all your help,
Martyn
Well, it sounds like he found exactly what he was looking for.
Another satisfied customer! Add him to your list.
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Bing187:Based on personal experience with 3 situations exactly as Martyn describes, I say to you:AMEN!
First, people are right when they tell you, "run it perpendicular and nail it on the joists. There's sags in the subfloors of new houses and the flooring goes down on them everyday. Use a straight edge on the floors and fill any sags over 1/16 with strips of felt, dont even need to nail them down. In bad spots, use more than one strip,ie: 12 inch- 6inch etc. just get it close. floor leveler is junk!. any floor I've repaired that had leveler applied before the floor was covered with floor levelor crumbles under the flooring. take a short piece of jatoba and try to split it with a hatchet this should answer your questions about it splitting. don't nail it too close to the ends Jim
Some think that the flexure between the joists will cause the tongues and grooves to break where the subfloor is sagging and doesn't provide enough support;
Martyn,
It was standard practice to lay T&G flooring DIRECTLY over the joists on covered porches at one point in history (I've seen it in the 1900-1910 time period, and I imagine the practice extends well into the Victorian period as well). What I typically see is 13/16" x about 3-1/4" fir flooring over joists at 16" centers.
I've also seen this same method on the interior of a number of houses -- usually the main floor had subfloor AND finish floor, whereas the second floor had the finish floor ONLY.
The reason for omitting the subfloor on the covered porches was so that water would not get trapped between the two layers and promote rot. I can only assume that omitting the subfloor on the interior was simply to save money.
The point is: the flooring has lasted nearly 100 years without unusual wear or breakage. Although it may not be the best approach, it is certainly not one that will rapidly fail.
The major difference in what you are proposing is the format of the wood -- fir was/is available in long lenghs, so the number of butts was minimized. Also, since there was no endmatching, the butts could easily be aligned over the joists.
With endmatched Jatoba, you'll have much more short pieces, and aligning the butts over joists will be more difficult. However, I like your approach of trying to lay out the flooring so that the butts fall where the plywood sagging is minimal. If you spend enough time on layout, I think you'll get "good" (not "superior") results.
Lots of folks here (myself included) have a tendency to overdesign. With that said, I'm hesitant to admit it, but I actually installed some Jatoba on a covered porch DIRECTLY over the joists about five years ago. The client really wanted to use that species, and since it is such a strong wood, I didn't think there'd be any problems in doing it that way. I thought the most important thing was to NOT have a subfloor due to the inherent problems of moisture entrapment. We only used boards of generous length and saved the shorter ones for interior use. Today, the floor still looks great and shows no signs of premature sagging or wear. I know it's only been five years (not 20, etc.), but I'm cautiously optimistic that the solution will continue to work.
Hope this information helps.
Ragnar-
My 1915 house had T+G fir flooring on joists on the porch, seemed to be holding up ok after 90 years. Not only that, it had the same fir directly on the joists in one room of the house (an addition). They weren't wearing quite as well as the other floors, and it was a bit more springy, but it was still there after almost 70 years.
Splices weren't a problem, since every board was knot-free vg fir the length of the room- just over 12 feet. If the wood wasn't so nice, I might have taken the whole thing up and put in plywood subfloor. I couldn't bring myself to rip up that old growth doug fir though.zak
"When we build, let us think that we build forever. Let it not be for present delight nor for present use alone." --John Ruskin
"so it goes"
There would be extra waste, but as long as the flooring planks end on a joist, that seems the most logical to me.Disclaimer...I'm one of those self GCing HO hacks, so take the advice for what it's worth.
You'll create problems for yourself that way, but what do I know....
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Maybe I'm missing something, but as you described your application I don't see a problem. If as you say, the plywood is the only thing sagging and not the joist, the oak flooring would be bearing only on the high point at each joist. Since you could install 3/4" oak flooring over and perpendicular to the joist without any sub-floor at all, I don't see that the existing sub-floor has to do with anything. As previously mentioned, care should be taken to avoid squeaking by using an adhesive and making sure the old sub-floor is screwed down really well. Also, nail at the joist only. I'm not familiar with the term "jatoba" and am thinking of standard oak strip flooring. This advice is free and you know what you get for nothing.
Martyn,
there is another solution that takes more work but won't require the leveling compund.
Plus it will dramatically stiffen your floor.
Are you interested?
I have a home built in 1900, had some termite damage in one bedroom and the floor repair done by Terminix was absolutely horrible (I'm being kind). We ripped out the replacement flooring and installed engineered flooring with the "extra thick" pad to make up all for the irregularities in the floor. The pad was almost 3/8 inch thick, looked like felt carpet pad with a plastic sheet bonded to it. Worked real well, the pad compresses over the high spots and tends to level out the surface. Of course, we were working on a real limited budget :-(
I have worked on houses that were at least fifty years old with tongue and groove oak floors, installed on 3/4" thick sleepers. Sleepers over joists, 16" apart - no broken tongues or squeeks.