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Fastener length for strapping

I finished installing a plywood ceiling air barrier directly onto the bottom of 24"oc trusses (ring shanked nailed) and I'm going to be installing 1x4 strapping at 16" oc to hang the drywall. What length of screw would be long enough to secure the strapping thru the plywood (1/2") and into the truss? I'll be installing 1/2" drywall. I'm thinking 3" screws but not certain.

What about the 3/4" gap the strapping creates, is it best to just leave that air gap empty between the plywood and the drywall? I don't really need the gap for wiring as the ceiling lights will be surface mount.

Also are 1 1/4 " srews sufficient to attach the drywall to the 16" oc strapping?

Thanks.

Asked by Smokey059
Posted Jul 12, 2018 7:57 PM ET

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4 Answers

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1.

Smokey,
Q. "What length of screw would be long enough to secure the strapping thru the plywood (1/2 inch) and into the truss? I'll be installing 1/2 inch drywall. I'm thinking 3 inch screws but not certain."

A. Both the plywood and the truss are good substrates capable of holding fasteners. I think that 1 3/4 inch or 2 inch screws are plenty long enough.

Q. "What about the 3/4 inch gap the strapping creates? Is it best to just leave that air gap empty between the plywood and the drywall?"

A. That's the usual method with strapped ceilings. As long as your plywood air barrier has sealed seams and a sealed perimeter (where the ceiling air barrier meets the wall air barrier), you should be fine.

Q. "Are 1 1/4 inch srews sufficient to attach the drywall to the 16-inhc-o.c. strapping?"

A. I always used 1 5/8 inch screws for drywall, but I'd be interested to hear opinions from other GBA readers.

Answered by Martin Holladay
Posted Jul 13, 2018 4:42 AM ET

2.

The reason I thought 1 1/4" drywall screws is because any longer and they will penetrate into the plywood air barrier and I reasoned that layer should not have screw holes into it. Or is it ok to have scew holes jnto the air barrier.

Answered by Smokey059
Posted Jul 13, 2018 7:46 AM ET

3.

I've never found the length of the drywall screws made any noticeable difference to either the susceptibility to nail-pops or the strength of the bond between the board and the framing. The first seems to be governed by moisture and shrinkage, the latter by the tear-out resistance of the screw heads and spacing of fasteners.

Answered by Malcolm Taylor
Posted Jul 13, 2018 11:03 AM ET

4.

Thanks for the help

Answered by Smokey059
Posted Jul 13, 2018 1:25 PM ET

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