# Spray foam insulation and glue???



## korby_17 (Jan 7, 2011)

Ok so I am a professional boarder and taper but I am going to be doing a job with spray foam insulation on a big vaulted ceiling and walls. I have never done one with this because it is a new thing where I am from. So since there is no poly can I just glue all the exterior walls and run maybe a couple screws in the field or screw off like a normall exterior? Also since there is no poly on the ceiling either would u recommend the same for that? Also I read on here that one guy said never use sub floor glue or pl400, why not I have used it for years with 0 problems. The job is framed 2x8 walls and the foam is only 4 inches thick so there won't be any pressure one the board. Also it is 28 ft. To the peak so there may be shifting if u think glue or screws would be better. 
Thanks


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## D's (Jan 15, 2009)

If its ceilings, glueing drops the required spacing from 12" to 16" meaning you'll still need 2 in the field. Not really worth it unless you're worried about screw pops. If the walls are spray foamed you can get away with 24" spacing with a mastic adhesive(PL or DSA), or 48" spacing with foam adhesive, in the field. If the ceiling has big spans, leave your perimeter screws 8" away from the edges to permit truss lift.


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## nu-wall (Feb 11, 2012)

I've been told that sub-floor glue will 'bleed' through drywall. Never tested that theory since I don't want to have that kind of problem. Glueing ceilings is much too messy anyway. Glue's nice on walls b/c if it's done right it will help level the surface on wood framing. Just be sure to screw enough to snug the rock into the glue and add screws if/where you have any rattles.


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## Tony Plain (Mar 2, 2012)

because you are going to glue to the studs any drywall adhisive is fine. I think the glue issue only comes into play when you are glueing directly to the foam, like EPS on Insulated Concrete Forms. The glue will eat away the foam unless you use a glue made for that aplication like PL300. I agree with D's regarding ceilings how ever I would suggest that leaving the screws back for truss lift is likely not going to be an issue. 2lb foam creates an excellent vapor seal eliminating the trusses exposure to humidity (at least in our dry climate). Also adds to the racking and structural strength of the trusses. 
If your foam guy is spraying ceilings onto your drywall lay the tapes 1st or even better use packing tape on the brown side to stop the foam from blowing through.


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## Final touch drywall (Mar 30, 2010)

Don't always believe what you read...all we use is pl400,never had a problem>>>>Only problem we have>>>>>Taking a board back down to do repairs sucs..Small itty bitty pieces is how it comes down.


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## SlimPickins (Aug 10, 2010)

Make sure the stud faces are squeaky clean of foam if you want a good bond.


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## nu-wall (Feb 11, 2012)

Could be that it takes a while for the bleed to show through paint and by the time it does the occupant doesn't have a clue - not that they would necessarily anyway. I don't have a specific experience to know with paint, although we have always avoided using it for standard drywall glueing because of that 'rumor'. However, I do know for certain that it will bleed through and stain vinyl board. I have seen it specifically on jobs that we have done where the installer ran out of our glue and borrowed some a carpenter.. The stains showed up within weeks and looked like you would expect - like someone spilled oil on it. I wouldn't take the risk. If it takes longer to show up the finger may never be pointed at you, but someone is stuck with it. If it shows up quicker, you're stuck with it. Either way it could be a very expensive fix. 
As a last resort one could always check with the manufacturer......


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## moore (Dec 2, 2010)

nu wall is right ...sub floor glue will bleed through the drywall.
seen it first hand:yes:


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## korby_17 (Jan 7, 2011)

Ok I got what your saying about bleeding through but what I am still unsure about is the walls. I have yet to do a job without poly on the exteriors so theoretically that should mean I can glue all of the exteriors. BUt I was talking to a guy who also has quite abit of experience and he thinks to screw off the perimeter and two on each stud in the field. I think perimeter and one in the field with glue and the reason I think that is because at big vault at 28ft at the peak there may be shifting and I thing there is more chance that there are going to be screw pops. glue holds and has give so it won't crack there for no pops correct??? Thanks hope that never confused anyone.


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## nu-wall (Feb 11, 2012)

IF you are going to glue what is the point of the screws? If you're going to screw, what's the point of the glue? 
Not only have I glued many jobs, but I have also demo-ed plenty that were glued. Glued jobs are MUCH more difficult to demo than either nailed or screwed. 
Proper glueing calls for around a 3/8" bead of glue started 8 - 12" inches from the edge and continuous to the same distance from the second edge. This applied to each stud except corner and butt studs. The sheet is then installed and perimeter nailed or screwed. Also when applying the glue keep it back from each side of the box a few inches. After you've confirmed that the cut-outs are complete and correct, screw a single screw in the field at any _known _weakness (like a really large cut-out). Then walk the sheet hitting at each stud with the side of your fist. If there's a rattle stick in a screw. Properly done glue actually corrects minor stud problems, increases the STC rating and holds better than any other system. Inside walls or outside, there's no need to screw unless there's a rattle. The glue also has elascticity and allows for movement in the structure without breaking the bond.


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## korby_17 (Jan 7, 2011)

Thanks that was what I was asking. I have boarded and taped for 25+ years but have not come across spray foam where I am from. I I'd not know what the specks were on that. Thanks nu wall. I figured that but I thought I would ask if there was a rule of thumb with fastening against exterior walls with no poly.


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## moore (Dec 2, 2010)

nu-wall said:


> IF you are going to glue what is the point of the screws? If you're going to screw, what's the point of the glue?
> Not only have I glued many jobs, but I have also demo-ed plenty that were glued. Glued jobs are MUCH more difficult to demo than either nailed or screwed.
> Proper glueing calls for around a 3/8" bead of glue started 8 - 12" inches from the edge and continuous to the same distance from the second edge. This applied to each stud except corner and butt studs. The sheet is then installed and perimeter nailed or screwed. Also when applying the glue keep it back from each side of the box a few inches. After you've confirmed that the cut-outs are complete and correct, screw a single screw in the field at any _known _weakness (like a really large cut-out). Then walk the sheet hitting at each stud with the side of your fist. If there's a rattle stick in a screw. Properly done glue actually corrects minor stud problems, increases the STC rating and holds better than any other system. Inside walls or outside, there's no need to screw unless there's a rattle. The glue also has elascticity and allows for movement in the structure without breaking the bond.


THANK YOU! I like this post. It's the way I was taught.


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## Bevelation (Dec 20, 2008)

You can glue on exteriors, but I didn't know it could be done on lids with reduced screw spacing. That's kinda cool, even though it's a difference of one screw less on lids, heh.


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