For flat smooth ceilings what is the best Type and brand of drywall to make sure they stay flat.  They claim the CD rated boards are better than 5/8 for ceilings. Reason for asking these questing is I hope to use cellulose for attic insulation but very concerned about ceiling sag 10, 15 years down the road. Could it be this be partly BS marketing just to increase there profits for 1/2" drywall?

I have the intent on installing trusses 16" O.C.


http://www.usg.com/content/usgcom/e...mbase.html

http://www.nationalgypsum.com/produ...uctID=2421

http://www.buildgp.com/toughrock-cd...rds/313698

http://www.americangypsum.com/produ...Fire-Rated

They all very well may all perform about the same boil down to lowest quote?

If you are subject to the building code, you might want to check with the officials to see if they require 5/8" for the ceilings.  My understanding is that 5/8" drywall is stronger than 1/2" and that is why some use it on the ceiling.  I do not know if any brand is better than another unless one is made in China.  Most builders just use what is locally available.  You might have to special order anything different than normal.  Some manufacturers are resistant to shipping less than a certain amount which might be more than you need.

Since the southeast is heavily infested with termites, you might want to look at paperless drywall.

One reason for using 1/2" gypsum ceiling board vs. 5/8" drywall is to reduce waste. Any leftovers from the ceiling installation, which should occur before the walls, can be used on the walls if it is 1/2". Not so if 5/8" unless maybe inside some closets.

If you are at 16" oc framing, you shouldn't have any concerns with cellulose up to R60 on 1/2" ceiling board or 5/8" drywall. Your drywall hangers may charge a bit extra for hanging 5/8" on the ceiling if it isn't the norm in your area.

The following thread discusses stabilized cellulose which should further reduce the load on the ceiling.

http://www.greenbuildingtalk.com/Forums/tabid/53/aff/14/aft/77306/afv/topic/Default.aspx

The links I posted are 1/2" products which have been formulated pacifically to be used on ceilings ....... They state it performs just as well if not better than 5/8" and very well may be true, there again it could be BS. Like most building products, time will tell if they are stating the truth ... if it is BS, like always the manufacture will place the blame on the installer or environment. Warranty's for building products are for the most part useless unless there are enough people involved to go after them under a class action law suit. Even than your chances of winning are slim to none.

The 8 year old home I live in now has 1/2" drywall 24" O.C. trusses and 7" of light weight fiberglass on the ceiling floor, and the crap is drooping. You can pretty much say that 1/2" drywall just alone 24" O.C. can't even support its on weight without sagging. And your telling me not to worry about 16" of cellulose on the ceiling floor

In New England the tradition is to strap the ceiling with 1x3 strapping at 16". This is usually done even if the joists/rafters are already at 16. You could strap your truss chords and give yourself 16" oc but you lose 3/4" of ceiling height. Strapping kinda make installing recess fixtures a pain but you shouldn't have any in an insulated ceiling anyway, eh?

Posted By ricky_005 on 09 Feb 2014 11:56 PM
You can pretty much say that 1/2" drywall just alone 24" O.C. can't even support its on weight without sagging. And your telling me not to worry about 16" of cellulose on the ceiling floor

No, I said 1/2" ceiling board, not standard 1/2" drywall.

I had to strap my trusses to get a flat ceiling anyway. It was a slow, tedious process shimming everything, but I found areas as much as 1/2" off, so it was worth it. The wood in most trusses is real crap these days. It's either that, or blow a popcorn ceiling and don't worry about it. I used 1X4 strapping, as the only 1X3 I could find was as bad as the trusses. I'm going with 1/2" ceiling board- time will tell if it holds up. With only 12-1/2" open space between straps, I should be good.

Ceiling drywall is stronger because of the fibreglas strands.

Sagging is more a result of moisture then weight but of course a combination of the two makes things worse. If you are in a high humidity areas, your ceiling will sag more then if you are in a dry area. If you blow on texture with the insulation already installed it will for sure sag. The board absorbs the water from the texture and is no longer stiff enough to withstand the weight.

Check the cost per truss before deciding wether to strap or close space.

@FBBP
Yes moisture was no doubt what caused it. The home was a foreclosure so was left unconditioned for some time .... When I get ready to sell it hopefully no one will notice the sagging drywall on the vaulted ceiling.

Its just very frustrating that there is no easy cheap solution to piling up the cellulose on an drywall attic floor of new construction without ceiling sagging somewhere down the road.

One option is to buy reclaimed polyiso roofing insulation in 4'x8' sheets of 2" or so thickness and rip it down to 22-1/4" wide and slip the sheets between your trusses on 24" centers after the ceiling drywall is glued and screwed to the trusses. This will help spread the weight of the cellulose on the ceiling so that it is primarily supported at the truss chords. I've often found 2" reclaimed polyiso for ~$0.20 per sq ft on craigslist or at www.insulationdepot.com. 2" of used polyiso would add ~R12 to your stackup.