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I moved into a house built in the 1920's several months ago that has a finished attic where the former owner's two teenage boys were living. I want to go from the old ratty carpeting to nice floor laminate for a yoga studio for my wife.

I assumed the subfloor beneath the carpet was the original old floor paneling that exists in the remaining unfinished part of the attic because walking around produces a lot of squeaking and noises. Upon removing the carpet I found my suspicions confirmed, so I will be removing the old ancient floor boards and replacing with 4' x 4' tongue and groove OSB boards. Upon starting to remove the original subfloor I saw that it sat on top of 2x6 ceiling joists without any blocking or cross bridging so I plan to add blocking for extra structural support.

There is also loose fill insulation under the current subfloor that looks like it's been partially removed over time and or was just never blown in to fill the joist space.

  1. Can I screw the blocking instead of nailing it as I'm a little worried the nailing might cause cracking in the plaster ceiling (with wood lath) below?

  2. Is it okay to sister a 2x6 board to the current 2x6 board along the front and back perimeter of the finished area to support the ends of the new subfloor since I'll be cutting the current subfloor back to the edge of the current 2x6's? Can I use screws instead of nails?

  3. Should I replace the loose fill insulation with unfaced batts and fill in any small areas with the old loose fill?

  4. Does all of this sound kosher / is there anything else I should be considering?

Here is a picture of the current space and a simple diagram of what I want to do.

Attic 1

Attic2

Diagram with blocking

  • If it's 85-95 years old and it hasn't fallen down yet, I kinda doubt it "needs" additional blocking...but knock yourself out. If it's heated/cooled, insulation between it and the other heated/cooled areas of the house is not needed. That would be a vestige of when it was an unheated attic. – Ecnerwal Apr 30 '15 at 20:46
  • That makes sense on both accounts. I didn't think the insulation was an issue but figured I might as well think about it. I guess the bigger concern is to find out if there is insulation behind the drywall of the attic ceiling. Though there is no heating or cooling in the attic itself... – Chris Apr 30 '15 at 21:26
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Can I screw the blocking instead of nailing it as I'm a little worried the nailing might cause cracking in the plaster ceiling (with wood lath) below?

Absolutely.

Is it okay to sister a 2x6 board to the current 2x6 board along the front and back perimeter of the finished area to support the ends of the new subfloor since I'll be cutting the current subfloor back to the edge of the current 2x6's? Can I use screws instead of nails?

Again, absolutely. Definitely makes things easier.

Should I replace the loose fill insulation with unfaced batts and fill in any small areas with the old loose fill?

Not necessary if over conditioned space, but would not be a problem.

Does all of this sound kosher / is there anything else I should be considering?

The joist are braced by the lath and plaster below on the bottom , and the subfloor on the top so no bridging will be needed.

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