Leveling sub-floor in 1870's house


Old 08-28-06, 05:14 PM
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Leveling sub-floor in 1870's house

I'm in the middle of a top down renovation of a circa 1870's detached brick "townhouse". The downstairs and second floor hall have 2-1/4" red oak strip flooring that was laid down 40 years ago and is still in good condition. We want to install similar in the BRs, which had carpeting over fur sub-floor, which seems very brittle. The joists (2” x 8” (actual dimensions) at 16” intervals) span 12’. I don’t know what kind of wood they are, but there’s no perceptible give in the joists. We usually refer to them as petrified wood, as it takes a good amount of force to screw something to them. They appear to be in good condition but the sub-floor is not perfectly level… varying about half an inch in a few areas.

What’s the easiest way to get a level sub-floor? In the largest bedroom (10.5’ x 12’), if we rip out the old sub-floor, and level to the highest point of the floor, that still leaves about 2” for sub-floor, underlayment and flooring to bring the BR even w/ the hallway. Can I just use 3” deck screws to attach 2 x 4 x 12’s directly to the joists? A plywood sub-floor could then be screwed partially on the actual joists and partially on the 2 x 4s, whichever was higher. This should leave us enough space to do 2 offset layers of 5/8” plywood sub-floor. Good idea? Bad idea? Very bad idea?

Also, will the above make the sub-floor stable enough so lay the flooring parallel w/ the joists rather than perpendicular? (Perhaps I should ask this 2nd question in the flooring forum.)

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Old 08-28-06, 08:01 PM
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Katalase: Welcome to the forums! You say the subflooring is uneven in certain areas. Is this due to deflection of the subflooring between the joisting or are the joists not level? If you remove the subflooring, you state you will still have 2" to hallway level. I would not use 2x4, but 2x12 instead to cover more area quicker and reduce movement. Glue them and screw them down. Then apply Advantech T&G subflooring. At this point it really won't matter in which direction you lay the flooring. However, it will matter when you get to the door to the hallway. You will have to make a transition piece and it may look better to have the flooring at opposite directions, but that can be a personal choice.
Old 08-30-06, 06:59 AM
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Thanks for the welcome and the advice! We've found great info here.

You ask: "the subflooring is uneven in certain areas. Is this due to deflection of the subflooring between the joisting or are the joists not level?"

The quick answer is: both. But I'm not concerned w/ the sub-floor since it seems that replacing it is the way to go. The joists are just not perflectly even, which may be partially due to the way the house was originally installed and partially due to some minor sagging and/or movement (less than .5") over the last 130 years.

Thanks again, Kat

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