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This is a follow up question to this old thread: Replacing hardwood floor in 100 year old house with no subfloor The house has hardwood floors installed directly on floor joists and the floors are very squeaky.

Since the floors are opened now as part of a larger remodel, I wanted to take the opportunity to address squeaking. To the extent that squeaking is caused by the extra flex in the boards in between the joists, below is a proposal to brace the floors by installing "subfloor" in between joists. My question is if I should use a binder layer between existing flooring and the subfloor that will be installed - the layer that is shown in blue. I was talking to one flooring person, and he said "No" since the blue binder would "prevent floor from moving". This seems counterintuitive since in the typical modern installation, subfloor is nailed to the floor joists and then the tongue and grove flooring layer is nailed to the subfloor, thus all layers are connected together transitively through nailing. It seems that the blue "binder" layer in the Proposed solution would be similar.

Since my floors are opened now, I can do a test to see if the Proposed solution addresses the squeaking and see it for myself. My only concern is around long-term implications that may not be apparent on Day 1. Such as, if binder layer does in fact prevent the necessary movement, this may take a season change to manifest itself, etc.

Which binder layer do you think best addresses squeaking and has no long-term negatives?

  1. Construction Glue
  2. Some type of caulk/glue that has some flex to it when is dry to allow for movement.
  3. Foam/rubber/some type of underlayment pushed up against the bottom of subfloor, but not glued.
  4. Nothing. Don't do it, because....

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  • Is like to see a detailed explanation of what this "sub floor" is supposed to do and how it works. Is this entirely to reduce squeaking? What sources of squeaking? How will this prevent it exactly? Can you mock this up in an existing open joist bay?
    – jay613
    Mar 4 at 3:22
  • Just a curious question, since the floors are up to a degree, how thick is the floor material? This will help determine how much deflection would be between the joists without the added "subfloor" At first thought, it does not sound like a good idea since the whole problem is caused by the wood shrinking since its construction. Now that it has definitely shrunk as much as it is going to, I see just resetting the floor, (if it is 1" thick) but that will have its own issues since the floor has shrunk too and will not match up with the remaining floor when set tight together.
    – Jack
    Mar 4 at 5:42
  • What does "the floors are opened now" mean?
    – Huesmann
    Mar 4 at 14:26

3 Answers 3

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The squeaking comes from weight of a person bending the floor.

In any and all cases I would not use glue since it will limit/restrict the normal floor extension and lead to floor deformation (in the hight). If you ever need to repair the floor, the glue will become a problem.

I would simply nail some support using 2x4 between the floor joists, and nailing it into the floor joist while flush mounted to the floor. That would provide enough support for the floor not to bend with persons weight and stop the noise.

Basically you are creating a support grid for the floors at 16x16 or 24x24.

If you decide to nail the floor to the 2x4 use 15-30 angle, so the nails do not come out from flexing.

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I would take the advice of your flooring person as I have never encountered or heard of your method being done to alleviate the problem of squeaks in floors.

The squeaks usually result from boards moving against nails. A common solution is to add blocking of 2x material perpendicular to the joists. This may not eliminate all squeaks. However it should reduce the number and it will help stabilize the floor by reducing the movement of the joists laterally. Then you could look for the squeaking boards individually and try to add support to those.

If your problem is that the flooring is too weak and flexes or dips when walked on I would think they need to be replaced, or a new subfloor should be added on top then your choice of finished floor.

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  • To clarify, the flooring guy liked the idea of bracing from underneath and this was also suggested in the original post. However, he recommended to use some type of a foam layer in between, Option 3, while I don't see how using glue/caulk to attach the two layers is any different than current install methods of using nails. Maybe the surface area of nail vs glue attachment is different, that perhaps the only difference.
    – ssm
    Mar 3 at 22:11
  • I'm kind of suspicious about using glue/adhesive. Glue would prevent the boards from moving and that may result in boards cracking and/or breaking. You really need the floorboards to be able to move to accommodate seasonal expansion and contraction. That's also why nails are preferred over screws as nails allow movement...which is where the squeaking comes from. A foam underlayment between the floorboards and the joists would prevent the floorboards from moving against the joists and prevent squeaks. Added bracing will help to prevent any deflection and that will minimize squeaking, etc.
    – gnicko
    Mar 4 at 4:00
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Easiest is construction glue on the top of the joists and in the grooves of the planks. Typical "panel adhesive" construction glue (most brands have "Nails" in the name) sets to a slightly flexible consistency

Trying to constuct a piecewise subfloor between the joists seems fraught.

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