Tip for anyone SR’ing over foam board
FWIW:
Because of a desire for a thermal break, a little radiant reflection, and an extra R3, I put 1/2″ foil faced foam (Thermax…Dow makes similar) in the inside of my exterior walls. Since I’m only a DIY sheetrocker, I didn’t immediately figure out why I was burning the screws through the paper so bad…didn’t have any trouble with this and my new drywall screw gun on the lid, which doesn’t have the foam board. Adjusting the nose cone back and forth only added to the trouble.
After a good deal of cussing, I finally figured out that once the board was hung with screws along the top edge, I had to screw sequentially along each stud, from tight to loose, top to bottom, to suck the rock against the foam a little at a time. There’s just enough “give” to the foam to actually angle the rock out enough so if you hang at the top and then start to screw off from the bottom…you’ll burn the screws right through the paper on the loose side. Unless you’re an animal and can hold that rock in really tight with one forearm and get the screw in straight with the other hand on the gun.
Really bad on the corners, where the foam thickness compromises the width of stud you have to shoot into, anyway, and the “give” makes it worse. Finally resorted to using conventional low-rpm/high torque cordless for those corner toe-screws. Better feel for when the srew plunges through the foam and starts to bite the stud. Some corner blocking would have helped.
Anyway, the idea of foam board under sheetrock deal has been brought up recently by several posters, just thought I’d add my .02 to save someone else a little cussing and save your screw gun a few hard smacks to the sub-floor ;<(. Those things are tuff!
Replies
Thanks, I'm headin down that road soon enough. Did ya use ANY glue?..and what about handnailin? would that make things easier?..I useally start some top nails and hang the board, then do like you said..screw the field, and the tapered edge. I do the butts ONLY after the next board is up..keeps the little blowouts from the edge from coming out.
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
No glue, although that might not ne a bad idea...maybe PL200 (?) between foam and stud.
The finer tip would be, don't screw too close to the edge of the tapered part of the board, as that screw is going through denser rock and compresses the foam more than if was in the field. I think any waviness will be taken care of with tape and mud, though.
Main thing is to go from tight to loose, top to bottom, middle studs to edge studs.
Also, along the edges of windows, it's really easy to break the rock , as, again, that foam compresses a bit.
Also, in my case, DW and SIL hung most of the foam, (a good project for them) using combination of shingle nails and plastic-button nails, then taped the seams, including the inside corners and around the outlet boxes. I was thinking the drywall screws would automatically pull everything tight, BUT, I found that I had to recheck all of those fastening points to make sure the foam was drawn up tight and no nails were 1/2 way out so they'd blow the rock out. Had to slit, nail, and re-tape all the inside foam corners too.
Probably should allow more time (and screws) per sheet in general when going over foam.
johnny.. whenever we use foam on the interior we always furr it.. you can adjust the furring.. put in blocking wherever you want it... blow insulation behind the foam.. etc.
then when it comes time to rock, you have good screwing and blocking whereever you need it for trim..
another thing about furring the foam.. you can pull you elec. devices forwar another 3/4 " so you can get mor insulation behind them.. and you have something to fasten the boxes to..
trying to rock thru foam is a bear...Mike Smith Rhode Island : Design / Build / Repair / Restore
Glad I'm not the only one.
Oh well, 15 of 25 sheets are already up, a little care will make it right.
Mike,
Great advise on the furring! That's how it should be done and I'm afraid in time the way it was done the screws will all pop.
I saw it done this way.... the rock was hung vertical... but the day before the sheetrock crew stacked the rock in 10 sheet piles face down over a 2x4 on edge in the center of the board so that the rock would "take a bow" they then used alot of glue and only nailed top & bottom using the "bow" in the center to make sure it held tite... worked like a champ..... no nails to pop ot have to finish... I've been wait'n for a chance to use that trick...
pony
What Mike said regarding furring strips, that's the only way to go.
If you're going to proceed rocking right over the foam, be real careful about sucking the rock too tightly against the foam. If you put the foam in too much compression, it's going to be working to un-compress...and slowly, but surely, you may just see several screw heads go right through the rock as the paper and gypsum core let go.
Another tidbit...next time consider gapping the sheets of foam about a quarter to three-eigths of an inch as you hang them. Then use canned foam to seal the gaps. Gets it real nice and tight.
Overall, good job using the rigid foam. It'll pay dividends down the road.
Did another sheet last night and took my time with the screw gun, getting the pressure just right. Actually did a kitchen/bath/entry addition, with rock right over foam (also a %$^%$&$ to do) that I've lived in for 10+ years. No nails/screws popped on thier own, but you really have to be careful installing anything on that sheetrock (plant hangers, light fixtures etc) because of the compressive nature of the foam underneath.
Edited 3/2/2004 8:46:40 AM ET by johnnyd