hello,

I have a 1/2" plywood subfloor, and I would like to reinforce it a bit before installing laminate or hard wood flooring.
Can I glue/screw on 1/4" OSB or should I go with 1/4" plywood?

Thank you

Add another layer of 1/2" CDX grade plywood. Screw it and glue.

Gary,

Thank you for the reply. The reason I want to go with 1/4" is that the adjacent rooms have the 1/4" addition. I will install the laminate throughout the 1st floor and I want to keep the same height. Do you think that I should replace the the existing 1/4" with 1/2" plywood and keep the same height throughout the 1st floor?

If you were to install 3/4" nailed down T&G hardwood at right angles to the floor joists, then the 1/4" plywood would most likely be ok, as the hardwood flooring will add some stability and rigidity to the subfloor. But if you use a floating floor or thinner hardwood, I'm afraid that 1/2" plus 1/4" may not be stiff enough. It depends on the distance between the floor joists. 12" OC it would work. 16"OC or more, could be flimsy.

Hi Gary,

The distance beween the joists is 16". I want to install laminate 10mm for now and in couple of years change it to 3/4 hardwood T&G. The reason I wanted to go with 1/4" plywood is because is less $$ and the guy at Home Depot told me that's ok to go with 1/4", but you know better.

Thank you.

Then compromise a bit. Try a section with 3/8" CDX plywood. Now, where I live, I cannot get 1/4" plywood in the lesser grades. So the 1/4" ends up costing as much as 1/2" CDX. But 3/8" CDX is commonly found around here and is usually the least expensive and should work pretty good for your requirements. I'm still partial to 1/2" but the 3/8" will suffice, I am sure.

Thank you Gary. I think I'll go with 1/2" CDX plywood, just to be safe.

Hi Gary,

Two more question. Should I install the 1/2" underlayment 4" from the joist centerline and 1/2 the width of the subfloor panel (as recommended by some contractors) or it doesn't matter as long as the underlayment end joints don't match the subfloor end joints? What screws dimension should I use and at what interval?

Thank you

I would shift the sheets, so nothing lines up with the sheet underneath, but have the ends on joists.