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Best practices for drywall in "attic rooms"?

We are building our house and are looking for advice about best practices to prevent drywall cracking in the "attic rooms" that will be built into the designed living space of the engineered trusses. We basically have a 14'Wide X 60'Long X 8'1"Tall space that will be the living area of our house; this is the "room" in the clear span engineered trusses over a 40' X 60' garage. The trusses are designed and rated for the proper live load and are spaced on 24"centers. The subfloor is tow layers of 3/4" plywood glued and screwed into the trusses. Originally I planned to use 1 X 4 furring strips on 16"centers up both knee wall and across the ceiling to fasten the drywall to, but I am now thinking that sheathing it completely in 7/16 OSB, glued and screwed to the knee walls and ceiling ( and then fastening the drywall to the sheathing, screwing into the "studs") would make a stronger structure and be less prone to movement and subsequent cracking of the drywall. What do you think?
I'll try to attach a couple of pictures in case I haven't described it well.

A. Spruce
Re: Best practices for drywall in "attic rooms"?

If the trusses have been spec'd and built for the load you're speaking of, then 5/8" rock on the ceiling is the only thing that will handle the 24" spans. 1/2" rock will suffice on the walls.

Re: Best practices for drywall in "attic rooms"?

Hello, A.Spruce is right. 5/8" on ceiling will be fine and 1/2" on walls is fine. I wouldnt waste more time or $ adding an other materials. The often problems that occur with these trusses are they are meant to move, twist, expand and contract. Best advise is use 5/8" & 1/2" sheetrock with DURABOND coating instead of standard(green or blue bucket mud)This is much stronger, less chance of cracking at joints. ALSO, use paper tape, it is 3 times stronger than fiberglass. The fiberglass stretches more than the paper and it tends to crack more. Hope this helps. ;)GregC Contractor 30yrs

Re: Best practices for drywall in "attic rooms"?
A. Spruce wrote:

If the trusses have been spec'd and built for the load you're speaking of, then 5/8" rock on the ceiling is the only thing that will handle the 24" spans. 1/2" rock will suffice on the walls.

USG makes a 1/2" high strength ceiling board that out performs 5/8" on 24" centers. Much nicer to handle overhead, and a better product too:


All the best,


Re: Best practices for drywall in "attic rooms"?

I have been planning to use the 5/8 & 1/2 all along and I've only used paper tape just because that's all I've ever used ( for what little sheetrock work I've done).

Here in the SouthEast, I've yet to see a truss room where the sheetrock hasn't cracked, even after just a year or so. Since this wiil be our main living area and not just a bonus room,I was hoping to avoid the problem if at all possible. Of course in hindsight, if I were to build it again, I would have spent the extra $'s up front and put the trusses on 16" centers, but even at that, I've seen many other houses with the 16" construction with the cracks. I assume it's due to the extream heat in the attic space in the summer months; to this end I have installed temperature activated gable fans in hopes of minimizing the peak temps in the attic and it has continuous ridge and eve vents too.

As far as the HD 1/2" being easier to handle for the ceiling; the ceiling is just a touch over 8' and I have a sheetrock lift to work with, so it shouldn't be that difficult to handle the regular 5/8". now if that HD 1/2" truly is better than the 5/8", that's something I will look into.

My plan has been to rock the entire 14 X 60 space (kind of like it's going to be one giant room) before I stand up my interior walls. I just figured it would be easier to work that way with less cutting and fitting of the sheets. Are there any concerns with doing it this way Vs framing up the walls and then doing the rock?

Thanks for all the input.

Re: Best practices for drywall in "attic rooms"?

because the spacing is 24 inch on center I would use 5/8 on ceiling and walls especially since this is an above garage room where you can expect at least some movement. on 24 inch spacing you will notice that the boards may bow slightly between studs if you use 1/2. here in florida in commercial construction if its 24 O.C. its 5/8. 5/8 will also make it more rigid. yea its heavier but sometimes a little extra grunting is worth the lack of problems later.

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