Sub Floor Reinforcement

rlc2052

My wood floors are squeaking and popping too much. The floors also seem very hollow when you walk on them. I have tried several remedies, but have come to the conclusion of pulling them up and reinforcing the sub floor. I currently have trim joists spaced out 20" with a sheet of 5/8" plywood on top. Would screwing down another sheet of 5/8" plywood on top of the existing plywood be my best option?
Sistering the joists is not really an option.

Thanks in advance

Termite

Although I'm unaware of your joists' specific spans, I don't think that's your biggest problem.

For a 19.2" (common spacing) on-center joist spacing, use of anything less than 3/4" subfloor is a mistake. So yes, adding another layer of plywood would be a good idea. In the old days, many people used a layer of 5/8" and a layer of 3/8", and it makes for a very solid floor.

These days, 5/8" plywood is for roofs and doesn't see much use on floors.

What type of flooring is on this floor?

You mention that it feels hollow. Can you elaborate? Do you feel the plywood deflecting between the joists under foot? Or is there noise besides the squeaking and popping?

The squeaking can be minimized by screwing the existing subfloor down to each joist every 8 or 10". I'd use 1-1/2" or 1-3/4" screws.

rlc2052

I took another look and the plywood subfloor is 3/4".
I have 5/8" bamboo floors in now.
The hollow feel is just from walking around or tapping you foot on the floor. The floor just sounds a little hollow in between joists. The floor is not deflecting from the joists.

Would a 2nd layer of plywood make a solid floor even if I put it in going around the walls? I do not plan on redoing the walls.

Termite

Your bamboo floor is probably a floating floor, which inherently sound "hollow". Bamboo is also a very hard material, and much laminate wood or prefinished wood flooring is thin, which probably has a lot to do with its sound properties.

There's probably/hopefully some sort of mat between the subfloor and the flooring, which should help with sound deadening.

If there are low spots or high spots in your subfloor, the increased gaps at the flooring would certainly make more noise when walking on them or tapping them.

Are you removing this floor and replacing it with something else?

I seriously doubt that the addition of more plywood will help your situation. Making sure the subfloor is level would certainly help.

rlc2052

I am planning on installing carpet on my third floor. I will need to put something down to raise the carpet to the level that the wood floors were at. The thing that I would like to fix in the process is that the floors shake some if you walk a little heavy on it. Little things will shake on the other side of the room. It is more of an annoyance than anything serious. I guess my question is would laying another layer of plywood help stiffen it up, or is it a lot more complicated to fix?

Termite

The shaking you're describing is due to deflection in the joists, not deflection of the subfloor. The addition of plywood will stiffen any "squishy" feeling that you get from any deflection in the plywood itself under load. But, it will add more dead load to the floor and will not do much of anything to stiffen the overall floor system. You'd need to stiffen the floor trusses themselves, which isn't going to happen without adding more of having an engineer devise a stiffening method. I think it would be a waste of time and money, except for the added benefit of gaining the height you need.

Not sure what your spans are, but 19.2" spacing is wider than I'd personally build a floor...Albeit allowable in many, many circumstances. The added stiffness of a 16" (or less) spacing is not a major cost factor at all at the time of construction.

rlc2052

So i guess that I should use something light to raise the carpet up. What would you suggest?