Subfloor issue for hardwood install

Discussion in 'Solid and Engineered Hardwood Q&A' started by baconsteak, Sep 13, 2019.

  1. baconsteak

    baconsteak New Member

    Hello and thank you in advance for any input. I am planning on installing some 3 1/4 x 3/4 solid maple pre-finished hardwood in the upstairs of my home. I have no experience installing wood floors but feel like I am relatively handy. The floors had carpet previously, I removed the carpet, padding and what I'm calling "homasote" it was 4' x 8' sheets of a paper board about 1/2" thick. The house was built in 1969 and I think this was original if that helps.

    Under the carpet, padding and homasote is 3 x 6 laminated t&g decking it has an actual thickness of 2 1/4" this runs perpendicular to large beams with a 24" span.

    Most of the subfloor looks pretty good and relatively level, but I did find a few spots that are not level. Here are a few photos. The gap under the board I put down for reference is about 3/8". I am planning to put the new flooring down with rosin paper and 2" staples. I am wondering how best to deal with this irregularity in the subfloor. This is the worst spot, it is in the back corner of a very small bedroom. What do you think?


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  2. Jim McClain

    Jim McClain TFP Owner/Founder Administrator

    I don't think I've ever seen an engineered lumber that thick before. Maybe you don't mean "laminated." I've also never run across decking used as a subfloor in a whole house. Is it the whole house, or just a room or two?

    Floor flatness should be measured with a 10' straight edge of some sort, like a piece of metal or a length of tall baseboard or even a tight string. In a case like yours, I might stretch a string across the whole span to see where the highest and lowest points are across rows of boards like that. A short 2x4 just isn't enough. You might find that you'll have to grind some boards down and fill others. Then cover the whole floor with a half-inch (min) layer of plywood.
  3. baconsteak

    baconsteak New Member

    Thanks for the reply. It is the entire subfloor on both the main and second floor. It is a laminated Weyerhaeuser product i found a stamp on a few of the boards, I'll try to get a photo. I will try your recommendation of a 10' straight edge and see what I come up with. I was really hoping to not have to add layer of plywood any chance if I get it closer that could work?
  4. Jim McClain

    Jim McClain TFP Owner/Founder Administrator

    If you can get the subfloor flat within 3/16" in 10', that would work.

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