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Esteemed Advisor
fredhargis
Posts: 1,890
Registered: ‎10-23-2009
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Vapor barrier in shop building.

I have a 24x32x8 detached garage I'm converting to my wood shop. The original plan was to put a vapor barrier all around the insdie after I insulated. The problem I didn't consider was that the previous owner had already turned 12x24 of the space into his shop, and he put a 5/8" drywall ceiling over that part with no vapor barrier(unfaced insulation). So now I'm considering skipping the barrier altogether since it doesn't seem like in a shop there would actually be that much moisture anyway (no plumbing in there, BTW). Or, If I have too, I could remove the existing ceiling (UGH!!!) or replace the insulation in that part with vapor barrier insulation. While I'm on the subjest, are trusses on 24" centers engineered to hold a load like 5/8" drywayy? I'll also be hanging lights and ductwork for a DC.

"I long for the days when Coke was a cola, and a joint was a bad place to be" Merle Haggard
Honored Advisor
mathisonr1
Posts: 4,071
Registered: ‎11-07-2009
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Re: Vapor barrier in shop building.

You should install the vapor barrier. How mad would you be if you developed a moisture problem down the road because you  decided not to install $25.00 worth of poly? I wouldn't worry about the existing area that isn't vapor barriered though. Yes, 24" on center trusses are engineered to hold the weight of drywall, ductwork and lights. When I was younger and didn't know any better, my brother and I would hook a come a long around a truss panel point and use it to pull engines in cars. I wouldn't recommend this though and neither do the truss manufacturers

 

Rick

Rick Mathison
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"I believe that to have a friend, a man must be one."
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Rrandy
Posts: 1,626
Registered: ‎11-05-2009
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Re: Vapor barrier in shop building.

Yeah, Murphy's Law for sure. A sub clause says something to the effect that you can get away with stuff as long as you don't know better. Once you know better though........

Never do anything you don't want to explain to the EMT.

Esteemed Advisor
fredhargis
Posts: 1,890
Registered: ‎10-23-2009
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Re: Vapor barrier in shop building.

 


mathisonr1 wrote:

You should install the vapor barrier. How mad would you be if you developed a moisture problem down the road because you  decided not to install $25.00 worth of poly? I wouldn't worry about the existing area that isn't vapor barriered though. 

Rick


 

 

Thanks, it isn't an issue of cost since I had already bought the poly. More like what good would it do if the 12' existing section doesn't have it. But I can go ahead and apply what I have...I may still pull the existing ceiling insulation and replace it with faced insulation.

 

"I long for the days when Coke was a cola, and a joint was a bad place to be" Merle Haggard
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RussBoyd
Posts: 7,956
Registered: ‎10-23-2009
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Re: Vapor barrier in shop building.

I agree with all the above but would add.... I think you can find a paint-on vapor barrier for that section of the ceiling that would paint over the sheetrock. I think. Just seems to me, I've heard of that. Anyway, worth checking out.

"If you can't hide it...advertise it!"
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mathisonr1
Posts: 4,071
Registered: ‎11-07-2009
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Re: Vapor barrier in shop building.

 


RussBoyd wrote:

I agree with all the above but would add.... I think you can find a paint-on vapor barrier for that section of the ceiling that would paint over the sheetrock. I think. Just seems to me, I've heard of that. Anyway, worth checking out.


 

Russ is correct, they do make topical vapor barriers. They are commonly used in commercial building renovations (usually on floors). You may have to go to a 'real' paint store and not one of the big boxes though. I dought that the kids at the local box would have any idea of what you're talking about.

 

 

Rick

Rick Mathison
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"I believe that to have a friend, a man must be one."
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fredhargis
Posts: 1,890
Registered: ‎10-23-2009
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Re: Vapor barrier in shop building.

 


mathisonr1 wrote:

 


RussBoyd wrote:

I agree with all the above but would add.... I think you can find a paint-on vapor barrier for that section of the ceiling that would paint over the sheetrock. I think. Just seems to me, I've heard of that. Anyway, worth checking out.


 

Russ is correct, they do make topical vapor barriers. They are commonly used in commercial building renovations (usually on floors). You may have to go to a 'real' paint store and not one of the big boxes though. I dought that the kids at the local box would have any idea of what you're talking about.

 

 

Rick


 

Man, such an item would sure make things easier...of to the paint stores today (actually, maybe tomorrow). Thanks, guys....

 

"I long for the days when Coke was a cola, and a joint was a bad place to be" Merle Haggard
Senior Contributor
monfre
Posts: 366
Registered: ‎10-23-2009
0

Re: Vapor barrier in shop building.

Yep there is such a paint, it's pretty close to the type of paints used in Bathrooms to keep the moisture from bleeding thur the drywall, if your unable to find the paint it would be in your best interest to get a vapor barrier up one way or another especially if your planning on having the shop heated i the winter time. Mold doesn't take long to start growing and once it does start it grows at a pretty good pace, for the few dollars and labor to replace and install the vapor barrier would IMO be money & time well spent and to give you peace of mind for you for the time you may live there and also knowing the next person will have a well build, insulated shop. 

Dan
Cedar Grove,Wi
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handyman john
Posts: 361
Registered: ‎10-21-2009
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Re: Vapor barrier in shop building.

As I recall VAPOR BARRIER is put in the WALLS to prevent moisture/heated air from moving OUT. Vapor barrier is NOT put into ceilings (or at least it didn't USED TO be).

 

I did note in my shop that moist air in the attic FROZE to to gable-end walls in winter creating about 1" of ice, but that was before I left the vents opened for the winter. This year I didn't have that problem.

 

Unless you are making the shop AIR TIGHT I'd work on the WALLS but leave the ceiling alone. Paint it and move on.

step one; understand the problem - the correct answer will follow
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mathisonr1
Posts: 4,071
Registered: ‎11-07-2009
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Re: Vapor barrier in shop building.

[ Edited ]

 


handyman john wrote:

As I recall VAPOR BARRIER is put in the WALLS to prevent moisture/heated air from moving OUT. Vapor barrier is NOT put into ceilings (or at least it didn't USED TO be).

 

I did note in my shop that moist air in the attic FROZE to to gable-end walls in winter creating about 1" of ice, but that was before I left the vents opened for the winter. This year I didn't have that problem.

 

Unless you are making the shop AIR TIGHT I'd work on the WALLS but leave the ceiling alone. Paint it and move on.


 

Check with a local builder to see if v.b. are code for ceilings in your area. IT IS CODE IN MINNESOTA.

V.B. on your ceiling will help keep moisture in your shop from reaching your attic space. Like Handyman John said though, make certain that the attic space is ventilated. Alot of garages around here are built without soffit and roof ventilation.

 

Rick

 

Rick Mathison
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"I believe that to have a friend, a man must be one."

 

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