I'd appreciate advice on the best way to stiffen an exisiting 5/8"
plywood subfloor on 2x10 joists.

I'm thinking of screwing down the existing plywood subfloor tightly to
the joists and then topping it with sheets of 5/8" plywood subflooring
laid perpendicular to the existing floor, and then I'd screw the new
subfloor down into the joists too.

Would this stiffen the floor to any significant degree? Would screwing
down the existing flooring stiffen it? Are there more effective (not
necessarily cheaper) ways?

Incidentally, there is no access to the joists from below.

Thanks in advance for all helpful replies.

Darro wrote:
I'd appreciate advice on the best way to stiffen an exisiting 5/8"
plywood subfloor on 2x10 joists.

I'm thinking of screwing down the existing plywood subfloor tightly to
the joists and then topping it with sheets of 5/8" plywood subflooring
laid perpendicular to the existing floor, and then I'd screw the new
subfloor down into the joists too.

Would this stiffen the floor to any significant degree? Would screwing
down the existing flooring stiffen it? Are there more effective (not
necessarily cheaper) ways?

Incidentally, there is no access to the joists from below.

Thanks in advance for all helpful replies.

How about if the reply isn't helpful? They still tried!

The second layer of plywood will do wonders. Screwing into the joists
is a must, but you should also screw the layers together between the
joists if you want the stiffest floor possible. Don't use drywall
screws, use deck screws.

R

Use construction or subfloor adhesive between the two layers in
addition to the screws.

According to Darro :
I'd appreciate advice on the best way to stiffen an exisiting 5/8"
plywood subfloor on 2x10 joists.

It really depends on how far you think you'll need to go.

We're renovating a bathroom (5/8" ply on 2x10 12" OC joists), which had
a lot of squeak and a fair amount of "play"/bounce.

Went over the plywood refastening it down with 2 1/2" screws, and the
linoleum installer covered that with 1/4" ply (not the traditional
birch 4x4's BTW), stapled it down and then filled the ply seams to
make sure there was no grooves to "telegraph" thru the lino.

Then they glued the lino to that.

Only used construction adhesive under the 1/4" in two small areas
where the T&G appeared to be non-existant in the original
subfloor, and the plywood joint wasn't perfectly aligning.
Glue was to keep the joint from moving/squeaking.

Zero squeak, floor's very solid now.

Might not be enough for a ceramic floor job, but it certainly was
enough for the lino.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.

"Darro" wrote in message
...
I'd appreciate advice on the best way to stiffen an exisiting 5/8"
plywood subfloor on 2x10 joists.

I'm thinking of screwing down the existing plywood subfloor tightly to
the joists and then topping it with sheets of 5/8" plywood subflooring
laid perpendicular to the existing floor, and then I'd screw the new
subfloor down into the joists too.

Would this stiffen the floor to any significant degree? Would screwing
down the existing flooring stiffen it? Are there more effective (not
necessarily cheaper) ways?

Incidentally, there is no access to the joists from below.

Thanks in advance for all helpful replies.

I did not see this in the other posts,

Make sure that the new joints are at least 2-4 feet away from the current
joints.

I am not sure that perpendicular to the existing will do any good. Plywood
spans the structure running with the structure does not span the weight out.

How about jacks under the structure at the half way point. That should
stiffen up the floor.

Plywood should help alot unless joists are the issue then who knows. Why
is there no access to them

Darro writes:

I'd appreciate advice on the best way to stiffen an exisiting 5/8"
plywood subfloor on 2x10 joists.

I'm thinking of screwing down the existing plywood subfloor tightly to
the joists and then topping it with sheets of 5/8" plywood subflooring
laid perpendicular to the existing floor, and then I'd screw the new
subfloor down into the joists too.

Would this stiffen the floor to any significant degree? Would screwing
down the existing flooring stiffen it? Are there more effective (not
necessarily cheaper) ways?

Yes it would. A house is being rehabbed next door and the owners are
doing all their own work. They double layered the subfloor on the 2nd
story they're adding for this very reason. I was able to walk up
there pre and post 2nd layer, and the difference is quite noticeable.

Best Regards,
--
Todd H.
http://www.toddh.net/