[Sanmyh]

I removed 3/8” laminated wood flooring from ¾” OSB subflooring. The glued areas damaged the surface of the subfloor where the glue beads were. I am installing ½” thick 3 ¼” wide engineered white oak plank flooring. The subfloor was not loose but I went ahead and rescrewed it to the floor trusses with deck screws. Do I need to install plywood underlayment. Is so could I get by with 3/8”? If I need it, how should it be fastened- screws into trusses, screws not into trusses, staples into trusses or staples outside of truss areas? Would rosin paper between the sheets be advised? I will use roofing felt under the new engineered wood. Thanks for sharing any experience with this.

 

[Nealtw]

How bad is the damage? can you post a picture.

 

[joecaption]

#1, Trusses are used in a roof, guessing you really mean floor joist.
#2, Yes on adding the tar paper.
#3, 1/2" flooring will span minor flaws with no issue.

 

[Sanmyh]

I think I have attached pictures of where glue tore off surface. The deepest areas are about 1/8" deep. I also included a picture of the floor trusses from an unfinished area in basement.

 

[Nealtw]

If you use a real underlayment they come with a pattern for the screws. Overlap the joins in the subfloor. I would rent a screw gun.

 

[huesmann]

If you're real worried about it, you could skim in some floor leveling compound to fill the divots.

 

[Sanmyh]

Thanks for help so far. Has anyone dealt with this before?
I'm getting multiple diverse opinions from installers, dealers, and online flooring sites. They range from "it shouldn't be an issue" to "fill divots, sand the existing subfloor and install plywood on top of subfloor." "Offset sheets and screw into joists" "Offset sheets and screw into subfloor outside of joist area" If I use screws, they will not have threads for the top part the thickness of the upper sheet.

The questions I have are-
1. Do I need to install plywood underlayment? (I was told over time, there might be an issue with the staples holding on the damaged subfloor, is that a credible issue?)
2. If so, what is minimum thickness of plywood?
3. How should plywood be fastened-
A. screws into trusses
B. screws not into trusses
C. staples into trusses or staples outside of truss areas
D. Glue
E. a combo of above
F. would rosin paper between the subfloor and plywood be advised?
I will use roofing felt under the new engineered wood. Thanks for sharing any experience with this. Thanks again to everyone.

 

[Nealtw]

As is would likely be fine until you have an end join in the hardwood right over a gap.
If you use some kind of filler, you need to be sure it would accept a staple with out shattering.
You had a very good sub floor before this happened, you just want a smooth surface on top.

Plywood 5/16 or more would give you that but I would be careful not to have join over one of these dips. And try to plan screw placement to miss the gaps.
If the subfloor is 3/4 glued and nailed and screwed properly there is no need to to match up with the joist or worry about screwing into the joists.

I am not sure what paper between the layers does but what ever you do some one will agree.