Replies

1. 
   xxPaulCPxx | Jul 10, 2006 01:21am | #1

   The problem with attaching drywall over Extruded Polystyrene is that where the screws or nails penetrate the drywall, it will also compress a small area around and under each fastener.  When you have a vertical line of them at a stud, the sum of the little compression points will give a valley.  Also, I would think that fastener pops would be a big problem.

   There is a way around this though.  You could use a decoupling device, like wood nailers or resilient metal channels (for sound deadening).  One side nailes though the foam and truss, the other connects to the drywall.  No waves translate through.

   Rebuilding my home in Cypress, CA

   Also a CRX fanatic!

1. 
   Piffin | Jul 10, 2006 03:37am | #3

   XPS does not compress enough to be noticeable at screws, and you want depressions there anyway for a smooth finish. The biggest disadvatage is actuqally finding the stud or chord to screw into.We use strapping at right angles to the framing over the foam panels like your "de-couplijng" suggestion. 

    

   Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

1. 
   ClaysWorld | Jul 10, 2006 09:39pm | #8

   Howdy, what's your thoughts on if your doing it why not use Iso instead of eps.

1. 
   Piffin | Jul 10, 2006 10:06pm | #11

   If I'm doing it, it is polyiso with foil face facing in 

    

   Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

1. 
   DocC | Jul 11, 2006 08:49am | #12

   Thanks for the help!

2. 
   Fonzie | Jul 10, 2006 03:02am | #2

   DocC,

   We have done that using 5/8 sheetrock over 1 inch blueboard or Rboard many times with no problem. It's true that the screw adjustment is critical, but that is always true. (we use 2 1/2 galvanized phillips deck screws).

   Sheetrocking over plaster ceilings we have put furring strips over the plaster (leveled with shims) and blueboard or rboard then 5/8 sheetrock over that.

   We have installed hidden splice boards (9 inch wide x 1/2 x 4 ft with a 1/8 x 1 inch strip stapled to each edge) up behind the blueboard to take care of necessary butt joints.

3. 
   zak | Jul 10, 2006 03:59am | #4

   Blueboard under drywall shouldn't be a problem, but I strap if the foam is thicker than 1".  It's a pain using 3" screws for drywall, in my opinion.

   zak

   "so it goes"

1. 
   donpapenburg | Jul 10, 2006 05:48am | #5

   I have done the three inch screw thing , it works , but a major pain in the a$$

1. 
   zak | Jul 10, 2006 08:47am | #7

   I'm glad it's not just me.  Even with 1" foam under there, I miss the studs more often than I should.zak

   "so it goes"

4. 
   basswood | Jul 10, 2006 06:04am | #6

   I would use this product on the ceiling. The InsulPink is 1.5" XPS in 2x8' sheets formed for 1x3's to fit flush. Use high-strength ceiling drywall sheets to minimize waves.

5. 
   Dudley | Jul 10, 2006 09:48pm | #9

   I have done it and use 21/2 inch screws and the plaster washers from McFeely's

6. 
   Mooney | Jul 10, 2006 09:49pm | #10

   I wouldnt want the job unless it was stapped . For me or doing for you , either way .  Definately . Remember that .

   Tim

7. 
   traini | Jul 11, 2006 02:49pm | #13

   On a different note I would use 3/4 strapping to allow a air space behind the drywall , I am a great fan of air space behind areas that could have condensation a air space keeps drywall dry and healthy and free of mold and allows for easy installation.

   George