I am in the process of leveling my floor with shingles and roofing paper. When using shingles, is it necessary to fill the two 1/4" gaps between the three tabs on a shingle with roofing paper to the same level as the top of the shingle?

Ummmmmm, generally, the shingles used for levelling are wood shim shingles. Guess you could use the roofing shingles you are describing, just never heard of it. I wouldn't worry too much about the gaps between the tabs

Dennis,

The 3 tab asphalt shingles can be used to fur up low places in subfloors. They can take the place of 30 lb. asphalt felt paper for flattening. I would only use this method for 3/4" thick, T&G hardwood flooring that will be nailed.

I never thought about using them for levelling purposes, but you are right, there would be no reason not to use them for a 3/4 inch nail-down floor. And they are easy to come by, lol.
What my guys usually do, is cut the wood shingles to proper length and lay them down back to back to level out a swale between joists.
Way back in the day, as a puppy, I would even use newspapar folded up to needed thickness. Got that idea during a rip out, and found a newpaper under the hardwood, dated on the day Winston Churchill died. sheesh.

Agreed! My first year in the business and I tried that on a floating floor. What a nightmare trying to correct as I went along further into the room.

Yet there's a video out there somewhere that shows the use of shingles for the same purpose. Folks must get confused. It could have been LL, not sure.

I spent some time looking at YouTube videos on hardwood flooring over the past few days...Yikes!

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I've only floored one room so far but when I tried using normal roofing shingles for flattening the floor I did not like the "hump" in the middle of them so I switched to "Hip & Ridge" pieces instead. Mine are Owens Corning: http://roofing.owenscorning.com/homeown ... pandridge/.
They are 36" * 12" and a little over 1/16" thick. I'm using them to "flatten" the floor in the next room I've started on as well.

Peter