unstaggered subfloor plywood 3

[darthsoilsguy2]

Doing a gut renovation on a 3-story residence and have come across a 3/4" plywood subfloor nailed to the 16" o.c joists, but the plywood is not staggered, nor was there any blocking for end seams. Curious what options are on the table to look at here that don't involve ripping out the subfloor or new staggered overlay.

 

[msquared48]

Glue and screw 2x4 FLAT on the underside at each of the unblocked seams...

Add additional interior shear walls to break up the diaphragms and lower the diaphragm stresses seen.

Mike McCann, PE, SE (WA)

 

[jdgengineer]

Review your diaphragm loads. The NDS gives values for other configurations of plywood other than the typical staggered joints. If it doesn't calculate out then block the panel edges as Mike suggested.

 

[dhengr]

Darthsoilsguy2:
Is there any evidence that the existing sub-floor diaphragm is in need of reinforcement, or not performing adequately? A 3/4" sub-floor is already about half again as thick as most of those installed today. I am always a bit floored (pun or not) at the people (background, experience, knowledge) involved in this kind of work. If I needed a heart transplant, I would most certainly want an OBGYN or a Dermatologist to do the operation, never mind a Structural Engineer.

 

[msquared48]

Well... also, without the blocking, the floor will squeak.

Mike McCann, PE, SE (WA)

 

[manstrom]

I specify unblocked 3/4" floor diaphragms all day every day. The edges are tongue and groove (normally) to lock together. No blocking required unless you have a high load diaphragms which is unlikely at a house. A staggered layout of panels is common and preferred, it is much stronger, but a checkerboard layout will also work just with a lower capacity.

If it ain't broke don't fix it. Just because it isn't normal to you doesn't mean there is a problem. If it squeaks, deflect or if the edges sag, then you could think about remediation.

 

[TehMightyEngineer]

Good point manstrom, is the plywood T&G?

Maine EIT, Civil/Structural.

 

[darthsoilsguy2]

It's not T&G. thanks for the input. Hearing the same off-line.