I know I have seen this mentioned before, but i can't seem to find it by searching. At which point do you shim with wood, as opposed to asphalt shingles? I have a low joist in a few places that causes a dip in the floor of 3/16 and some about 1/4 inch. Can I shim these up with shingles and 30lb felt before adding my 1/2 CDX underlayment, or should I use wood?

Thanks for the help. This is the floor project from hell! 3 months and I still don't even have the underlayment down! But without this forum i would be lost.

Nick

If they are no more than a quarter inch you can use shingles.

Thanks Jerry. Is there anything bad about having to use alot of shingles to get the floor "flat" ("alot" in quantity not thickness)? Cause right now on a 12x20 room I am going to have section of shingles and felt paper (to taper the dip at the ends) that stretches all the way across the 20 foot room in the middle and is 5-6 feet wide. It looks like 2-3 shingles will flatten the dip at its lowest point and then I will have to use a single shingle and felt paper to feather it out and this will make the section 5-6 feet wide. Like half my subfloor will be covered in shingles before the 1/2 CDX underlayment goes down...is this a problem?

Nick

I might get you in trouble here Nick. Lets start over. How thick is your subfloor and can you get to anything from underneath. It sounds like you have a low area spanning a few joist but, it could very well be one high joist causing this apparent low area. For instance if you have 2x10's they should measure 9 1/4", but I have seen them as much as 9 1/2" before and had to R&R the subfloor and plane them down.

Well what I thought was a low joist is instead a bunch of joists which are sagging in the middle. The house is 80 yrs old and has 2x8s (which are slightly larger then todays 2x8s) spanning 11-11 1/2 feet on 16 inch centers and over the years many of the joists have "settled" and sagged in the middle. Now there is no way I am getting that sag out of them considering they have been like that for 50+ years probably.

It is a full basement so I can get to underneath everything, but I likey have the same problem on the 2nd floor which I am hardwooding and will not be able too. THe current subfloor is 4 or 5 inch long tongue and grooved boards that are 3/4 thick and run perpendicular to the joists.

Low areas of 3/16 to 1/4" are not that that bad really. You can layer a few shingles and felt then overlay with the 1/2" plywood ( I prefer BC grade for this instead of CDX).

I was going to suggest you could drive shims between the subfloor and joist to raise the subfloor. But having 1x's sort of throws that out. You could think about driving the 1x's up, then sister on some 2x6's or 2x8's on the swagged joist to level it out. The 1x's are not glued and might be better for the first floor.

Sweet...thanks for the help Jerry.

Considering the size of the section that needs shimming, would it be better to go with luan or some 1/4 wood in these spots....or will the shingles be fine?

Nick

I would prefer the 1/4" plywood over shingles if you can get it to work. I like having something to nail thru.

Gosh is this thread really 3 years old? Someone is not reading the rules.

Missed this spammer. By the way if any of you guys see posts like this ...let me or Keith know so we can delete and ban. That's why it was a thread that was so old.

angiebuds
Post subject: Re: How big of a low spot can you shim with shingles?
New postPosted: 04 Nov 2010 12:25 pm
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The most common is the ¼ plywood for the shingles. If it is few layers then you might use ½. It will be just fine for the shingles.

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Last edited by angiebuds on 05 Nov 2010 04:40 am, edited 1 time in total.