T&G chipboard flooring fixing over ply diaphragm

[Rick734]

Evening all,

 

Just wondering if anyone can advise with a flooring query. I'm doing a TF extension on top of existing single skin garage walls, and the SE has specced a 9.5mm ply diaphragm over the joists, with flooring substrate to go over that (nothing specified for the actual flooring substrate so was going to use 22mm Caberdek). My chippy was saying they'd obviously glue and nail the ply onto the joists, and will use 63mm nails down into the joists through the ply anyway, but was then asking if I want them to glue the chipboard down onto the ply as well. 

 

Any thoughts on this? I just want to prevent any squeaking or movement - is adding or not adding glue between the ply and Caberdek likely to have any impact either way?...

 

Thanks

 

Rick

*edited for clarity

Edited Tuesday at 21:26 by Rick734

[Rick734]

Couple of pics for reference...

[MortarThePoint]

Curious as to why the SE has specified the plywood at all.

 

Squeaks come from rubbing and if both the plywood and the T&G are glued at the joists there shouldn't be any scope for rubbing 

[Rick734]

Thanks @MortarThePoint - apparently a diaphragm to prevent racking or something like that. Pretty sure he's overengineered the whole thing but better safe than sorry I guess...

 

Helpful - so basically glue and nail then to prevent any chance of rubbing at all...

[MortarThePoint]

Gluing and nailing the plywood feels OK, but I'd glue and screw the T&G to the plywood at the joists. Then the screw is clamping both the plywood and the T&G to the joist.

 

So yes it's gluing the T&G to the plywood, but only at the joists. I'd also glue at the T&G short edges if not at joists, already gluing if at joists. That would add strength and may avoid need for noggins.

[MortarThePoint]

I'm pondering what force the nail from the nail gun would clamp the plywood to the joist with in that first gluing operation. I'm much more familiar with screws, but I expect the nails should make for a tight joint which is what you need to avoid an excessively thick glue layer. The Chippy will definitely want to use his nail gun for this bit so I wouldn't be suggesting screws unless someone more knowledgeable than me has concerns.

[torre]

Another alternative might be to fix the diaphragm to the underside of the joists, but you'd have to check with your SE. 

[Rick734]

Thanks guys - super helpful thoughts. I'll run them past the chippy today and see what he thinks 😃

[iMCaan]

My joiner used expanding glue (I believe it was D4) and a nail gun.