I am new to this forum and am looking for advice on flattening a subfloor so that I can install 3/4″, 2-1/4″ wide Birch flooring.
The situation I have is this:
I have a first floor great room and dining room with finished basement below (drywall ceilings). After removing carpeting and baseboards I discovered the subfloor is like a washboard several joist had crowns turned downward and one joist is high. I would like to avoid removing subfloor, because I do not want to redo the basement ceilings and my house is small and have kids and I do not want them walking on or through the ceiling below :).
The subfloor is about 1/2″ low at the lowest point. The valleys are irregular, i.e like a topographic map.
I have the book “Hardwood Floors” published by Taunton but the author does not go into a lot of detail about flattening a subfloor.
Here are some of the solutions that I have come up with or have been suggested:
Using shingles and felt paper to fill in low spots.
Cut shims and place in-line with floor joists, then use a leveling or patching compound screeded to the shims. Nail flooring at shims, then use trim head screws in between.
From the aforementioned book, the author shows a diagram of an out-of flat subfloor and shows shims spaced 8″ o.c. on top of and parallel to joists when you are going to put a plywood underlayment on top of the shims, or 4″ o.c. when you are not putting new plywood underlayment.
I am not sure what to do. I am a do-it-yourselfer, but no experience in this realm. I am certain the structure is sound. I did the basement, I had to run 1×4’s perpendicular to joist and shim to get level. I could see liquid nails & shims between subfloor and joists and did not really think about a possible problem. I also was trying to avoid a new underlayment for height gain. But I just would like some feedback on any of these solution or alternatives.
I also get the feeling that these leveling compounds are not made for nailing through, again I do not know anyone have any experience with these?
Thanks in advance,
Tim Lawler
Replies
Tim,
I had a similar problem in my house with the entire first floor,(approx. 1200sq. ft.) except it dipped in some places as much as 2.5"! I had very good success using a method similar to your thought on placing shims over the joists except that I laid down a second subfloor over the shims and drove 6" ringshank spikes through the whole thing, then laid down hardwood over it. I learned alot of do's and don'ts during that project, so if you consider going that route, I'll pass them along.
Thanks for the reply, I will mull this over and would certainly appreciate any tips that you might have.
Thanks in advance,
Tim
I understand the desire in avoiding pulling up the subfloor.....unfortunately thats the best way. By trying to satisfy your short term concerns (children around open floor) you will probably be sacrificing your long term gains (a better job). Keep the kids outta there for the few days you may need before closing it up. You`re not saving any time or money by leaving the sub floor down. You`ll be much happier in the end.
J. D. Reynolds
Home Improvements
"DO IT RIGHT, DO IT ONCE"
I appreciate your input!
Bear in mind I am not a contractor:
If I remove the subfloor won't I end up ruining the ceiling below or at the minimum cracking up the spackling below? How do I remove subfloor at outside walls? Doesn't the bottom plate sit on top of the subfloor and bandjoist? How do you support this and the new subfloor? Would I have to continue on into adjoining rooms?
What is wrong with shimming and maybe overlaying with 1/4" plywood?
Can the leveling compounds be used or not - satisfactory?
Just trying to understand all the options and learn as much as possible.
Thanks again for any further light you could shed on this subject.
Best regards,
Tim
>If I remove the subfloor won't I end up ruining the ceiling below or at the minimum cracking up the spackling below? Not necessarily. Be as careful as you can, and be prepared for minor touch ups. How do I remove subfloor at outside walls? Doesn't the bottom plate sit on top of the subfloor and bandjoist? Yes it does. Come in one joist from the outside wall and cut subflooring down center of joist. You`re not going to remove that which is below wall plates. How do you support this and the new subfloor? Would I have to continue on into adjoining rooms? No....same here.....stop tear up one joist short of adjoining rooms.
> What is wrong with shimming and maybe overlaying with 1/4" plywood?
The void below 1/4" ply between high and low spots will not support finished flooring.
> Can the leveling compounds be used or not - satisfactory?
The nails used during flooring installation will destroy the work you`ve done with compound.
Best of luck!J. D. Reynolds
Home Improvements
"DO IT RIGHT, DO IT ONCE"
Jaybird:
Thanks again for the help!
>Not necessarily. Be as careful as you can, and be prepared for minor touch ups.
I know that the subfloor has construction adhesive and power nailed (heads are barried about an 1/8" to 1/4" into sheet) are there any good methods to removing while doing a minimal amount of damage below? Should I cut on each side of joist and then try to use a recip. saw to slice the nails and cut through the glue or just set blade to 19/32" and cut down center of joists and use prybar and/or catspaw and start pulling/prying out nails and break adhesion bonds?
>No....same here.....stop tear up one joist short of adjoining rooms.
Along one outside wall running parallel with joists subfloor is 1/4" low, to complicate matters along this same wall at the far end this transitions from great room (most problems) to dining room. How would you handle this?
Would you put blocking between joists where you stop cutting and walls run perpendicular to joists. That is blocking that is half under old subfloor and half under new?
> The void below 1/4" ply between high and low spots will not support finished flooring
What about building up low spots completely with something like shingles or roll roofing and felt paper and overlaying with 1/4" plywood? I understand that this is not as clean as having a new subfloor. Again, I am just trying to weigh all the options and understand the pros and cons.
I cannot believe that no one ever invented a nailable leveling compound. This seems like it would be in great demand.
I was wondering if you could screed out dry sand and trap it under a 1/4" ply and nail it or would it move around?
Thanks again,
Tim
I have seen sand used under floating floors to auto make up dips, but I think in the case of nailed flooring, it would move away and cause you problems later.
__________________________________________
Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
Calvin,
I was not sure, I have done some brick paver work and thought if it could support bricks it might work but you dont shoot nails into it every 8-10" either.
Thanks,
Tim
Tim; For pulling the nails you need a nail puller. They are specifically designed for the job you are getting ready to do. They are mainly useful in pulling nails from subflooring though they could also be used elsewhere. The tool I'm talking about has a pair of pincers that grab the nail head, a vertical body with a slide hammer action, and a right angle foot that serves as a lever arm and also tightens the pincers when you start pulling the nails. They are easier than a cat's paw and quicker.
Clay,
Thanks for the tip! Where might I get one of these?
Thanks,
Tim
Tim; Apparently the old style is no longer being made (though you can probably get one on E-bay or at a flea market. Here is a newer version that is still available:
http://tools.ontheweb.com/shop/cooper-group-56-nail-puller___1_B00002N7SD.html
These will really dig down for the nail head and you can get by with lots less damage to the ply than a cats paw will cause. Much faster too.
Clay,
Thanks so much for the information!
Tim
> I could see liquid nails & shims between subfloor and joists
Was this just here and there, like somebody trying to fix squeaks after the fact, or was it a thorough liquid nails everywhere job? The answer to that will determine whether it makes sense to try to get the existing subfloor up and shim under it, or leave it and shim over it. If you do go for pulling up the subfloor, make yourself a bunch of wedges out of scrap 2x, and drive them in to break the glue bonds.
-- J.S.
John,
Under the great room which is where the problem is the worst it was pretty well glued, there were shims in several locations. I honestly do not remember, how much shimming because at the time I did not think about the subfloor being a problem.
Thanks,
Tim
It's the adhesive more than the shims that makes the difference. If it's a little bit crammed in from the sides after the subfloor was down, like to try to fix squeaks, that would be fairly easy to take apart. But if they put glue on everything as it went together, forget about trying to pull it up. Shimming on top will be easier in that case.
-- J.S.
Thanks for the input! I am leaning toward the shimming at this point.
Tim
You might try pulling up one of the smaller pieces of subfloor along one edge to see if it was all put down with adhesive. If not, pulling it up and shimming under it will be lots easier than shimming on top.
Since you're doing this yourself, you could do one sheet at a time, just starting to pull the adjacent one up before you put the old one down. That way you could do only as much as you could finish and close up by the end of each day, leaving a child-proof surface between times. A professional would want to pull it all up at once, rather than spending the extra time to change tasks on a sheet by sheet basis. Watch your step, don't drop any heavy tools, and your ceiling below will come thru this just fine.
In any case, start by going thru the whole room with a laser or water level, a measuring stick, and a sharpie. Write the corrections you need to make on the subfloor, like "+5/16", etc.
-- J.S.
Not a bad idea, I might do that if the first partial sheet gives me a lot of trouble than I could just drop back and shim on top. I really like the idea of closing things back up.
I have a rotary laser, but if I go for level won't this open a whole new can of worms? Like where the great room transitions to the dining room. Flat is really all that I am after at this point, although the floor is pretty close to level high spot to high spot.
Thanks,
Tim
Tim, buy a bundle of underlayment wood shingles. Lay a straight edge on the floor and shim to height. I doubt whether you will have much shimming to do, it looks worse now since you pulled up the carpet.You can shim as you lay the flooring, but shimming first is easier. I tack the shims down with a 18 gauge brad nailer with 5/8" brads. This keeps the shims from moving while you are sliding the flooring around, but easy to move if you are a bit high or low.
I don't lay floors for a living but I believe this is the best way short of removing the subfloor.I would visit a flooring company and ask them about the gypsum leveling compounds. This may work and it would be easier than my method.
Mike,
Thanks for replying.
What are underlayment wood shingles and where do you get them?
Do you shim just along joist lines or fill in the whole area?
Thanks in advance,
Tim
Tim, underlayment shingles are what carpenters use fro shimming door frames, any type of shimming.They come in a bundle, any lumberyard or Home depot will carry them.Shim every 12" or closer for 3/4' flooring.You can shim the entire low spot if you want. One bundle of shingles will do a lot of shimming. You will have plenty left over I would think. I do not recall what they cost but they are very inexspensive.
Mike,
|underlayment shingles are what carpenters use fro shimming door frames, any type |of shimming.They come in a bundle, any lumberyard or Home depot will carry |them.Shim every 12" or closer for 3/4' flooring.You can shim the entire low spot if |you want.
Are these like cedar shingles varying widths and lengths? Or are you refering to the uniform packs of shims that I see at Home Depot, Lowes, etc.
The book I had gotten "Hardwood Flooring" the author showed a diagram saying shim every 8" when putting a new layer of plywood over shims or every 4" without.
In your first reply to me yesterday, you made mention of shimming everything first or shimming as you laid the floor. What do you think is the best way to proceed?
Thanks in advance,
Tim
Tim, I am referring to cedar shingles, the widths are random the lengths are 18".I found it easier to shim an entire area first. If you only need an occasional shim here and there , then I shim as I go.Make sure the flooring nails go thru the shims. If the area that is low is large , shims should be no further than 4" between shims with 3/4" flooring.I am assuming the flooring is tongue and groove.I suggest that you shim all the large areas first.
Mike
Mike,
Thanks, I figured that is what you were talking about. I really appreciate the help!
Best regards,
Tim
Mike,
What are your thoughts on overlaying the shimmed subfloor with 1/4" plywood. Do you think it is worth the additional time and money?
What are your thoughts on Warneford's post about adhesive and crown stapling the shims?
Thanks again,
Tim
Tim- Assuming that you sub-floor is in no other way unsuitable, it is best to place a new plywood floor over it. Removing glued and screwed, or nailed flooring is an unpleasant task. This is of course if the new height will not be a problem to doors, and other entry ways,etc.
If this height will not work , You must have a min. of 5/8 flooring to accept 2/4 by 2 1/4 flooring, to have enough wood to accept and hold the nails or staples. A 1/2 hollow filled with paper is like nailing into air , since the nails are going in at an angle, will hardly go into the wood sub-floor. That being said, only use solid shims, with a small bead of construction adhevsive and brads, or preferably 3/8 narrow crown staples.
Also, any nail down floor should be under a flooring compound not more than a light 1/8 of an inch. Any deeper in depth and the compound can and contrary to popular opinion will crack when nailed and fragment later, giving a wonderful light cracking sound as you walk over it, not to mention the lack of holding power. Avoid floating compunds for nail down application except for the smallest of dips!
Time and patience is your best approach here. Or is that Tim and patience.
Warneford,
Thanks for the feedback.
I guess I will try to avoid the compounds if at all possible. If I do have to use something I will stay at 1/8" or less.
I could live with a 1/4" of new plywood over any shimming of low spots but any more than that begins to be troublesome at doors and 1"+ transition down into another room is more than I really more than I would like.
Do you think that I would get a better job by shimming to flat then overlaying with 1/4" plywood not luan? Then proceeding with felt paper and flooring?
Thanks in advance,
Tim Lawler
I have a couple of questions..Is your home old ?What are the dimensions of the room? A 1/2 inch doesnt sound like much to me if the room is large.( dont get me wrong it shouldnt be like that but thats the way it is) Iam not a professional floor installer but Ive done plenty of wood floors and of those, Ive never been called back for a floor prob. maybe Iam full of crap, but ive installed wood in some really old homes and the sub floors go all over the place, the 3/4'' t&g flexes enough to follow most dips in the floor and gets nailed down tite,also if your worried about it flexing as it bridges a dip between joists ..it wont at least not much... enough to feel. youve never felt your plywood sub floor flex have you?For extreme sags or dips i would slide a shim under the new wood only where needed.Is the plywood sub floor just puffed up along the seams?? If so i would just feather the edges with a large disc grinder with say some 36 or 60 grit sanding disc, I might even be tempted with following the subfloor above a joist with a little to much crown then re nail or screw.try to avg level the floor over the area of the room. I have a Sioux grinder i use for such situations.I dont think you'll notice any dips etc once you get the floor installed and put your furniture ,throw rugs etc. in the room. tearing out the sub flloor thats glued and nailed with a finished drywall ceiling below sounds like alot of extra work and overkill for little gain.(and i love a little overkill when warrented) if its really really bad just put carpet back in and forget about it. Remember your putting a floor in not making struc. repairs.Iam not trying to be a smart #### either when i ask this last question Do you think that if bought the floor installed (from a local flooring tile carpet store ) would the floor installer tear out and shim up your subfloor to do their install?Maybe someone here that puts in wood floors everyday would chime in on solutions for uneven floors with sags and dips. great question and i love reading the solutions posed.. good luck
Xray,
Thanks for the input.
The room in question here is about 18'x12'-6". The house is about 16 or 17 years old. The flooring is 19/32 T&G Plywood on 2"x10" joist on 16" centers. I have rescrewed entire floor with #8 x 1-3/4" screws hoping to flatten things out a bit. The problem I believe is that several joists were crowned downward and one is high. I might be able to grind an 1/8" off the high spot but that takes me down to 15/32" on the subflooring at those points.
I am not interpreting your comments as derogatory. You are right an installer would not do this. All I am trying to do is figure out the best option. I have called a flooring store that sells a lot of hardwood and tried to as how it would be handled and I really haven't gotten an answer. I just want to put down the flooring and not end up having problems with overwood, creaking, looseness and open joints because of not properly flattening my subfloor.
I thought about putting carpeting back in but I bought the wood flooring 8 months ago and I have been to busy till now to put it in.
Best regards,
Tim
Hey thanks for your comments,Iam just trying to save you some work I cringe thinking about you pulling up that subfloor.Dont forget your going to have to scrape off that glue too.thats a big room and I dont think anyone including you would notice it if you do nothing but shim here and there as needed. I didnt say it before but my guess would be to expect moderate to severe damage to the drywall below if you start trying to remove the subflr. you'll probably have some anyway when you start banging on that floor nailer.I dont think the floor will open or squeak if you install it as is.Take a couple of pieces of flooring and test a few courses across the low spot and see if it doesnt belly down into it. Also keep in mind that at some point maybe after you move out of the house the floor will shrink or expand and open up. theres no guarantee against it because it's wood and it moves. while I here your concerns I dont think the problem is severe enough to warrant the removal of the subflr. Its not a pool table.And there will be other imperfections only you will know when your done and all houses have them some worse and better. I dont believe in doing anything half way either its just the way the situations layed out.Start laying the floor you'll figure it out ...good luck
Xray,
You have been a great help, just when I thought I might try pulling up the subfloor. You scare the heck out of me!
You are right, though its time to get off the pot, and start laying flooring. I will bring it in out of the garage tomorrow and start shimming and probably lay flooring next weekend after it has gotten acclimated.
I want to thank everyone who has replied, for the very helpful advice. I have learned a lot.
Thanks again,
Tim
Hate to tell you this but unless your garage has exatly the same humidity levels as you great room your going to have to leave it in teh G room for 3/3 weeks/3 months (depends on the installer fussiness. You want the flooring to have the same moisture content as it will maintain when installed otherwise the changes will cause cracks/buckles to open up. THe good news is now you can spent some more time working out your leveling strategies.
Thanks for the input. I will move it in over the weekend and I was planning on buying or renting a moisture meter to test wood until it comes to equilibrium.
One question, I have a very small house (1300 sq ft) alot of this is going to be hardwood. Can I move the wood into my basement (carpeted with dehumidifier, pretty low humidity levels this time of year) while I level floor and then move into areas it is to be used in to finish acclimating it?
Thanks,
Tim
I think it will be fine.stack it on a couple of 2x's not directly on the carpet. If the wood is in boxes pop open the ends.Spread it out in the rooms 24 hours before you start laying it.I think you can skip the moisture meter but if you feel more comfortable checking with a meter it cant hurt.Its winter like you said so its probably pretty dry already. P.S. leave the laser level in the box.Why dont you start in one of the smaller less public rooms (easier to hide a mistake in the kids bedroom) before you tackle the big one and you'll probably discover all of the same challenges the great room has shown and be ready for them and you'll feel 100% more confident about what your doing.
Thanks for the help!
I will start moving the wood in tomorrow.
I really appreciate all the helpful feedback from you and everyone else.
Tim
I would go with xray's suggestion. 1/2 inch is not a lot and you may just want to shim as you go. My floor was 1 1/4 inch out and I had to shim all the way. Slow but beats ripping out the subfloor.
Tom
Thanks for the feedback.
Tim