Replies

1. 
   Edgar76b | Jul 30, 2002 03:30am | #1

   Not only that It may be a fire code.

1. 
   MikeR | Jul 30, 2002 03:57am | #2

   If fire code is not a concern, they do make 1/2" ceiling board which is reinforced to resist sagging.

   Mike

2. 
   Mooney | Jul 30, 2002 04:19am | #3

   If you put 1/2 on the ceiling and put insulation on top of it , it will bow between joists . Using ceiling board [1/2 inch fiber board ] will barely get you by , but not if its holding insulation. Installing insulation after finishing is done helps a great deal. It will always sag if there is weight  on it when texture is blown. You have to go to 5/8s to get fire code rating you need and the strength to hold up on 24 inch spacing.

   1/2 inch ceiling board is best with 19.2 centers . Regular 1/2 on 16 centers, and walls.

   Tim Mooney

1. 
   brownbagg | Jul 30, 2002 06:39am | #4

   what happen is, two bedrooms got 1/2 board before I could stop them. It is already up and mostly finish. I would hate to pull down. this is screwed on 2x4 trusses on 24 centers. with r11 between trusses. I making them put 5/8 rest of house ceiling. The r11 get r30 blown on top. R11 is mainly a filler due to electrical, ceiling fan boxes etc. If I add some wood on top of trusses to support the r30 additional taken the load off the drywall. Will this help. Is a 1/8 inch that much differents in strength. What I mean is , not hearsay or theory, have anybody actually saw 1/2 sag due to insulation weight. How much does r30 weigh?

1. 
   TooManyTools | Jul 30, 2002 06:53am | #5

   Just as a matter of strength of materials the stiffness varies as the SQUARE of the thickness.  In other words 5/8ths has 25/16 the strength of 1/2" or more than half again as strong.

2. 
   Mooney | Jul 30, 2002 06:53am | #6

   I hate to say this , but yes Ive seen it for 35 yrs. Its real . I cant make an alternet  suggestion but what it is . Sheetrock was never intened to support insulation . It just gets abused daily.

   Tim Mooney

1. 
   HeavyDuty | Jul 30, 2002 10:06pm | #11

   I think sprayed pop corn finish will sag the ceiling more than the weight of insulation, don't you think?

   Tom

1. 
   Mooney | Jul 31, 2002 03:15am | #13

   The thing with acoustic spray is that it has 50 gallons of water per 1000 sqare ft. IIt soaks up the entire feild, and weakens it for a period of time. Thats the reason I say no weight on it untill its dry. Its only lime and paper !!!!

   Tim Mooney

2. 
   brownbagg | Jul 31, 2002 04:34am | #14

   I found the differents in 5/8 to 1/2, yes its only 1/8 bigger but I swear it 70 lbs heavier.

3. 
   Mooney | Jul 31, 2002 04:43am | #15

   It should be against labor law to hang 5/8 x12 on the ceiling. I know its not healthy. I never had a problem hanging 1/2

   Tim Mooney

4. 
   HeavyDuty | Jul 31, 2002 06:01am | #17

   I thought the weight of the wet 1/2" dry wall itself is enough to make the ceiling look wavey after it dries, even without the insulation on top.

   Tom

5. 
   Mooney | Jul 31, 2002 06:09am | #18

   It is if its not sufficient .

3. 
   Piffin | Jul 30, 2002 07:08am | #7

   I mostly use 1/2" but also strap at 16"OC. I have seen sags in 1/2" at 24" OC but not to terrible for a small bedroom. Easiest fix would probably be to hang another layer of 1/2" with glue and longer screws in those rooms for insurance bu if walls are already hung too that is not really advisable.

   It is not just the weigfht of insulation that is to be feared. It is the life-long action of moisture and gravity on the actuall SR that causes the sag. It is worse in rooms like kitchens and bathrooms.

   Excellence is its own reward!

1. 
   Mongo | Jul 30, 2002 04:46pm | #8

   I always use 5/8ths on ceilings, though I have to mention that I frame with TJIs. 

   It gives more strength, more stiffness, and more protection for the TJIs from fire.

   I also use 5/8ths on exterior walls, though half-inch is used on interior walls.

1. 
   Piffin | Jul 30, 2002 06:21pm | #9

   Do U not use any bridging or blocking or strapping to stabilize the TJIs ?Excellence is its own reward!

2. 
   Mongo | Jul 31, 2002 03:50pm | #19

   Piffin, yeah, I strap the TJIs. Looking back my sentence could be considered a bit muddled. Instead of:

   "It gives more strength, more stiffness, and more protection for the TJIs from fire."

   I probably should have written:

   "5/8th's has more strength and stiffness than half-inch gypsum board, as well as offering more fire protection for the TJIs."

3. 
   Mugsy | Aug 01, 2002 07:25pm | #22

   Been meaning to ask you.  What specific polyiso board do you use.  Any particular brand preference?  I'm gonna use your system for the first time on a dormed out Cape with cathedral ceilings renovation I'm doing.

4. 
   Mongo | Aug 07, 2002 06:07am | #23

   Mugsy,

   Sorry for the tardy reply...I've been off-line for the past week.

   I've used both Celotex and Homasote polyiso.

   Celotex calls their's "Tuff-R", Homasote calls theirs "Ultra-R".

   I use them interchangably, as one yard carries one, another yard the other. When I need quantity and neither yard has enough I'll buy from both and I will mix and match.

   The differences? I can't mix the 2" versions on the same plane (ie, wall or ceiling). The 2" Ultra-R is 2" thick, but the 2" Tuff-R is less...about 1 3/4" thick. The Tuff-R also has fiber strands in the foam which makes it stronger, but slightly messier to score and snap.

   If I had to stick with one version, it'd be Homasote's Ultra-R.

   If you have any other questions, feel free to fire away.

5. 
   Mugsy | Aug 07, 2002 07:43pm | #24

   First of all, no need to apologize.  I don't expect instantaneous responses.  You do have real work to do, I'm sure.  Thanks for the info. Yard I usually deal with has Tuff-R.  I will ask about the Ultra-R, but I,m glad to hear from someone that uses it regularly that it shouldn't matter. I'm only going with the 1" though, which leads me to another question.  What do you attach your furring/strapping with when using 2" boards? I believe you said you furr out.   I can't imagine attaching drywall directly over top with what, 3 1/2" screws? 

6. 
   Mongo | Aug 10, 2002 06:12am | #27

   Work to do?

   The hardest work I've been doing over the past couple of weeks was trying to find an internet cafe in Moscow.<g>

   "Live, from the northwest corner of Red Square...it's Breaktime!" Click the mouse, take a sip of vodka...click the mouse again, take another sip of vodka...

   Well...trying to decipher the Cyrillic alphabet can be hard work, too.<g>

   I use 4" screws for attaching 3/4" furring over 2" foam. With the screw head sunk into the furring, it gives about 1 3/8" of purchase into the framing. I'll have the drywall screwed into the furring with standard-length screws...either 1 1/8th or 1 1/4" screws depending on what's getting hung where.

   As an aside, for furring, I've ripped strips out of 3/4" ply as well as used yard-bought furring strips. It seems a shame to rip a sheet of CDX ply into furring, but sometimes it does make sense. Occasionally the quality of the strips the yard carries really stinks. Too many knots, too much wane, you cut the banding holding the bundle together and they flip into unusable pretzel-shaped pieces of soon-to-be kindling.

   If you're hanging the rock yourself and want a bit more margin for error, rip some strips 2" - 3" wide, and use those under the seams in the rock for a bigger target to screw the rock to. I'll use leftover pieces of furring cut to fit vertically between two horizontal runs of furring and slip those behind the butt joints of the rock as the rock is hung. Screw the ends of the rock to those and they'll lend plenty of rigidity to the butt joints. This way, the sheets of rock don't have to break over a structural framing member, either.

   Going back a bit, if your framing is 16" oc, don't sweat trying to lay out the strips so they break over a framing member. When furring over thick (1" or more) foam, they can break mid-span and they'll still be rigid as heck.

   Think about blocking as well. For example, if you know something is going to be surface mounted or hung on a wall or ceiling at a certain location, pop a piece of ply blocking over the foam and between the furring strips where the blocking is needed. The blocking doesn't even have to be screwed into framing if the location deosn't allow it. I'll pop a couple of beads of adhesive on the back of the blocking and mash it against the polyiso, the drywall will eventually sammich it in place. Ensure the blocking is the same thickness as the furring...3/4". 

   A while ago Mike Smith posted some detailed pics about how he hangs electrical boxes when running foam and furring on exterior walls.

   Edit: Forgot to add...don't sweat the choice between polyiso's. If Tuff-R is what's available, Tuff-R would be fine. I simply think the 2" Ultra-R is easier to score and snap because it has no fibers.

   Edited 8/9/2002 11:19:47 PM ET by Mongo

7. 
   Mugsy | Aug 12, 2002 04:33pm | #29

   Thanks for the info.  I know you've posted this stuff 100 times, and I've read most of them.  Was just curious if you had brand preferences.  Glad to see you don't.  I have fairly well stocked yards here, but only if you want what they carry.  Anything else can be a royal PITA.  Hope you're enjoying your trip.

8. 
   Mongo | Aug 12, 2002 08:56pm | #30

   The trip was great...back home now...weeding the garden...playing catch-up all around...ugh.

   ...where's my passport?<g>

9. 
   rez | Jul 30, 2002 08:29pm | #10

   hey mongo- how come your using 5/8s on the exterior walls?Half of good living is staying out of bad situations.

10. 
    rez | Jul 31, 2002 05:20am | #16

    Mongo- Being one always wanting to learn, I was wondering what your reasons for using 5/8inch sheetrock on your exterior walls are. I am curious in that maybe your reasons warrant that I might begin using the same. Thanks.Half of good living is staying out of bad situations.

11. 
    Mongo | Jul 31, 2002 04:45pm | #20

    rez,

    I don't think my reasons will provide the "smoking gun" logic that you're looking for. In many ways the 5/8ths could be considered overkill...but it's what I've ended up with for a few reasons.

    First, the 5/8ths on the ceilings gives better burn protection for the TJIs. While I'm not a fire protection fanatic, I have worked with the local fire department in the past and I realize that TJIs, when exposed to fire, will lose structural strength faster than standard 1.5" timbers when hit by fire.

    Continueing with ceilings, I often frame the floor joists at 19.2" instead of 16". That increases, however minimal, the chance of gypsum sagging when installed on a horizontal plane. Though strapping often brings the spacing back to 16", I still prefer the added strength the 5/8ths affords over half-inch due to the blown-in insulation.

    Third (kind of already mentioned), all joist cavities in the house get insulated. I always use RFH and virtually always blow in cells. The 5/8ths on the ceilings gives greater strength against deformation caused by blown-in insulation.

    For the exterior walls, again, it first offers better fire resistance to the shell of the home. Again, I don't build, nor do I recommend building to satisfy for all contingencies...however remote...but the fire protection is an added bonus. Often I'll use polyiso on the exterior walls as well...that's another story in itself...and it's nice to have the 5/8ths-inch fire board protecting the polyiso from flames. Nasty toxic fumes when that stuff goes up in smoke.

    When I first built my own house, I framed the exterior walls with 2-by-6's, 24" oc. I felt that with the increased stud spacing, the 5/8ths would offer better strength for the insterior walls. It certainly does. You'll notice the difference pushing against a wall skinned in half-inch vs 5/8ths inch with the studs 24" oc.

    Again, blown-in cells tend to displace the gypsum board. 5/8ths offers better resistance to deflection than half-inch.

    The 5/8ths on the walls does mess with standard jamb widths (wall thickness) for window and door trim. I take advantage of this by adding a small filler strip...1/8th to 3/16ths or so in thickness, as needed..."picture framing" the edge of the window jamb so a bit of the jamb edge is shown as a reveal...and then installing the interior window trim over that. The 1/8th-inch filler strip adds a bit more detail, another shadow line, to the window/door trim, and that strip is used to correct for any drywall irregularities instead of having the casing itself do battle.

    I got into building after pounding nails solo to build my own house. People came by and asked me to "make one of those for me." Some of the details, some neccesary for better-than-average construction, some seemingly extravagant, have carried over. Many people look at the 5/8ths as a security blanket. Better fire protection, stiffer walls and ceilings.

    Is it neccessary? Is it better? Is it neccessarily better?<g>

    It does add a few dollars to the cost of building. In a typical house I run about 240 sheets of 12' boards. At a couple dollars more per board for 150 of those sheets, there's another few hundred dollars or so in materials cost. The rocker's don't charge a premium for hanging it, though I tip them VERY WELL at the end of the job.

    In the end, yes, I personally do think that the 5/8ths is superior to half-inch. That's based upon how I build as well, as well as the related methods of building that I include in the house. By related methods I mean framing spacing, blown-in insulation, TJIs, etc. Add in a bit of what the customer wants and there you go.

    Again...not a smoking gun, but maybe a smoldering, slow burn?<g>

12. 
    rez | Aug 01, 2002 06:04am | #21

    Thanks much. Definitely good food for thought.Half of good living is staying out of bad situations.

13. 
    Mooney | Aug 08, 2002 06:59am | #26

    good job

14. 
    Mongo | Aug 10, 2002 06:15am | #28

    I appreciate the kind words, thanks, Tim.

3. 
   Mooney | Jul 31, 2002 03:06am | #12

   Drywallers schedule for quality work ;

   1/2 inch reg drywall on 16 inch centers for ceiling use.

   1/2 ceiling board [fiber reinforced ] 19.2 centers for ceiling use

   5/8s fire code [fiber reinforced] 24 inch ceters for ceiling use .

   Tim Mooney

4. 
   kenboston | Aug 08, 2002 02:27am | #25

   I like to strap everything ,I dont care how true the TJI or truss can be.

   Reason; the electrition can run his wire without penitration and strapping

   will give you more surface to screw your 4ft butt joints.