Hi!

I am planning to put engineered hardwood floor down in a home I just purchased (built in 1975). Subfloor is in pretty good shape. It is

1/2” plywood with 1/4” OSB nailed on top. I know that the standard is 3/4” subfloor for engineered but I am concerned because I know that 1/4” OSB is not really worth much in terms of strength.

I would prefer not to tear this up or build it up because it is a huge pain and sheet goods are so costly but I will do it if have to....I was just planning to screw the two sheets together to decrease creaks and move on.

Hoping to have your opinion?
thank you!

Subfloor:



Example of thickness (looks a bit thicker due to some flaring at the edge here but it’s 1/4” OSB)

 

What is the spacing between your floor joists?

In your last photo it appears there is another layer underneath the plywood. Is that the case?

What does your flooring manufacturer require for underlayment?

 

That extra layer seen below is just part of the stairs (it’s the only place I could easily get a picture of the subfloor layers).

The joist spacing is 16”

and the underlayment is 3mm cork/foam.

 

Welcome to the forums!
If you have any floor registers that would be a good place to double check your subfloor. It would be odd for the subfloor to only be 1/2" and I'd expect it to be a little bouncy. The 1/4" OSB adds no structure.

 

What do you think I should do about it?

 

I'd remove the 1/4" OSB. If the subfloor is one layer of 1/2" plywood I'd add another layer.