2x4 trusses and 5/8 drywall ceiling

Question

Here's what I have; 50 year old construction. 2x4 trusses, spaced 22" centers (2nd floor). Running 28ft in length with a beam in the middle (14ft). For my ceiling I have nailed up 1" blueboard (Hard Styrofoam) directly to the 2x4 trusses.

Getting ready to hang my drywall. I have screwed in 1x4 furring strips every 16". My plan is to screw the 5/8 drywall into the furring strips.

Question being: will my ceiling handle the weight?

Hello again, Sorry for being so confusing. I would send a pic If I was able. I do not have pic of the trusses or anything like that at the moment. Yes, I do have cellulose (13") in my attic (rafters). Picture if you will; A ceiling that runs 28' wide and 38' long, with a 6" beam running perpendicular down the middle of the trusses (bottom of trusses). The trusses are made using 2 -14' 2x4's spanning the entire 28' distance, there is a beam smack dab in the middle where the trusses are fabbed together with 1/2" plywood gusset. there was drywall nailed directly to the bottom 2x4 of the trusses at one time, I just don't know if it was 1/2" or 5/8". So what we now have is 1" rigid foam nailed to the bottom 2x4 (bottom of trusses) and 1x4 furring strips screwed through the rigid foam and into the bottom trusses. Now comes the hanging of the drywall. I am not so concerned with the 2x4 trusses holding the drywall as much as I am the 1x4's being able to hold without sagging. Is screwing into (say) 5/8 inch wood going to be enough depth to hold up drywall, Being that I have 5/8 inch going through the drywall as well. It is old construction (50 yrs). So we're not talking normal. there isn't anything normal about this house.

Answer 1

The weight of the foam and furring strips is negligible. I'm not sure why you installed the furring strips unless you're concerned that the drywall will pull in when you screw it on, but they don't weigh much.

Anyway, the weight probably isn't a concern. Use lightweight no-sag half-inch drywall if you have reason to think that the ceiling joists were taxed originally, but the additional weight of an eighth of an inch of gypsum won't likely break the camel's back.

Answer 2

The problem is not the attachment of the drywall to the 1x4 furring strips. Ultimately the ceiling is being held up by the screws attaching the furring strips through the blue board to the trusses. 1x4s have a tendency to split when you screw them near the end of board. You can predrill before you you screw in the furring strips at the end of board. However, when you go to attach the drywall you will want to put any screws near the end of the furring sttrip to be at least 3" from the end of the strip or your drywall screw will definitely split open the furring strip which now has two screws near the end of the board.

P.S. The 5/8" drywall will not sag between furring strips spaced at 16" o.c. even is the furring strips might have a slight slight tendency by itself under the same load. Think of trying to sag a piece of paper it two perpendicular directions at once.