Repairing de-laminated plywood sub-floor 1

[MichaelP1011]

I have a residential developer/builder client who received a "bad" batch of 3/4" 5-ply T&G plywood which was installed by glueing and nailing onto wood "I" joists. Post installation the top and bottom layers de-laminated.

My client wants to know if there is a way to replace the affected panels without ruining the top chords of the wood joists. Also does the loss of the T&G edge treatment adversly affect the strength of the floor?

 

[samdamon]

Michael-

First off it sounds like you need to remove the plywood. If it is delaminating on top and bottom faces then the assumed composite action of the plywood and joists in a glue-nailed system is going to be reduced or eliminated. The plywood's rated carrying capacity as a deck is also obviously affected. The overall floor will be less stiff and strong as a result.

It's possible to remove glued and nailed plywd from the joists. Had this problem in a residential repair a year ago (although the joists were 2x10's not tji's). It takes some care and a bit of muscle, but a sawzall blade and some judicious use of prybars and shims will allow you to cut through the nails just above the top flange of the I joists. The sawzall can also cut through the glue if a typical construction adhesive was used. If the bottom ply of the plywood deck is delaminating that may make this easier. Obviously you want to be careful not to cut or notch the top flange of the I joists- any loss in section will weaken them.

Not sure how to answer your second question. The APA glued floor design tables I have assume that the t&g joints are glued as well as connection of the deck to the joists. Would say delamination will weaken the desired effects of glued t&g joints, but this sounds like a lesser problem than the ones discussed above.

Good luck.