Drywall over foam board insulation

[clemsonfor]

I am wanting to know if what my title says has been done by anyone (the blue stuff, foam that is not drywall)? I did breif reasearch on the net and have heard both. Several with no nail pops or trouble, others say that you cant do it cause of a moisture barrier. But i see no difference than blue foam under drywall vs the plastic vapor barrior, both will trap moisture behind the drywall as both will have insulation behind them in this case?

What im proposing. In a remodel of my upstairs i want to atleast put the ridgid foam on the ceiling before i put my drywall over it. I have those ceiling tiles on it now, the 12" by 12" kind. I really dont want to pull them down so was just gonna rock over them but thinking about getting more insulation i was thinking blueboard first. There is 6" batt insulation in the void now, half the room has the ceiling attached to the roof joists and the middle is a flat part with ceiling joists (if this makes any sense). Meaning that half the room is slanted like the roof and the other has attic space over it.

I also want to think about doing it on the walls?

What are you guys thoughts?

 

[bp fick]

Me? Since you're gonna have to re-hang the drywall anyhow? I'd just demo the old stuff and be done with it. Jam extensions, outlet boxes all set wrong, what a pain. With a tear out, you can then be sure everything is right. Or, call Mike Holmes of Holmes on Homes, and listen to him crab for awhile.

The demo cannot be THAT bad. I'd just tear 'er out and do it like a new build.

 

[davedj1]

You should have no problems doing what you desire. Just make sure that the screws don't get driven too deep (easy to do over foam). I don't want to alarm you but the fumes from the foam are extremely toxic in the event of a fire. We've used Hi-R sheating under the drywall too, you get a higher R rating with less thickenss. I don't have the figures here at the moment but you can look up the R rating for 1" blueboard and compare it to 1/2" Hihg R. The thinner you make the inslulation the easier it will be to screw the sheetrock over.

Don't mind the spelling errors, I'm under the influence of muscle relaxers at the moment:licking:

 

[tmajor]

Well, I've done exactly what your proposing, regarding the insulation under sheet rock With 2 exceptions: My house is "double plank", so it breathes pretty well. The other thing is, I used the white insulation with the foil on one side. I haven't had any problems. ... with condensation or nails popping, however, I did use screws. I believe the insulation was 1".

With your upstairs ceiling, you HAVE to have an airspace between the insulation and the roof boards or you'll get condensation, you can't imagine. I'm referring mostly to the part, which runs with the roof.

 

[RRILEY]

If you already have 6 inches of insulation in there why the blue board? And how thick are you talking about for that? Are you in South Carolina? I have rental property and you will regret just covering up a problem and not fixing it right, especially for your own home.

 

[RRILEY]

Like Tmajor said the roof decking needs air flow to vent and dry out to prevent rot and mildew and stink and water stains etc. etc. etc.

 

[BHD]

I have done similar, using the foil faces foam, (now our house was boarded up on the inside, with ship lap lumber,

one mistake I felt I made was not putting some wood striping around the windows, for some thing solid to nail to,

makes some things hard to work with, with the thickness of not any thing solid, to work with,

I would do it again tho knowing what I know, but would most likely use 3/4 thickness, and fur out the windows and a 1x4 on the floor and would not hurt to put something at the ceiling for some thing solid to nail/screw to,

I use what was called a box extension, a small sheet metal thing with tabs where the screws are, and it slipped inside the box in the wall, and held with longer screws in the receptacles,
this was what I used, Inspired Remodeling & Tile | Nashville, TN | Peter Bales, Contractor | Play it Safe With Outlet Extensions
it appears they make a plastic version of it as well,
PVC Electrical Box Extenders for Tiled Backsplash - Brings your outlets out flush with the wall.

 

[tmajor]

My house, being "double plank" had no problems nailing or hitting wood, unless you hit a crack between boards. There were no receptacles in the walls, due to the planks and the house was built before electricity was available. So, I had to cut into the first plank for part of the box depth and the insulation took care of the rest. The wires were run up the cracks between the planks.

 

[clemsonfor]

Me? Since you're gonna have to re-hang the drywall anyhow? I'd just demo the old stuff and be done with it. Jam extensions, outlet boxes all set wrong, what a pain. With a tear out, you can then be sure everything is right. Or, call Mike Holmes of Holmes on Homes, and listen to him crab for awhile.

The demo cannot be THAT bad. I'd just tear 'er out and do it like a new build.

I am gonna do the ceiling most likely the walls, Maybe? So the only boes i have to worry about is 2 ceiling boxes, not a big deal.

 

[clemsonfor]

You should have no problems doing what you desire. Just make sure that the screws don't get driven too deep (easy to do over foam). I don't want to alarm you but the fumes from the foam are extremely toxic in the event of a fire. We've used Hi-R sheating under the drywall too, you get a higher R rating with less thickenss. I don't have the figures here at the moment but you can look up the R rating for 1" blueboard and compare it to 1/2" Hihg R. The thinner you make the inslulation the easier it will be to screw the sheetrock over.

Don't mind the spelling errors, I'm under the influence of muscle relaxers at the moment:licking:

Yea, im not to worried about fumes in a fire, id hope id be outta there at that point, if not i have more to worry a bout.