Vapor Barrier? 2

[abusementpark]

What type of vapor barrier do you usually spec for most commercial projects?

I see some engineers still spec 6 mil, most do 10 mil, and some are going to 15 mil.

 

[Ron]

ABP...assume you're talking about slab vapor barrier. 6 mil is sufficient, provided joints are taped or lapped 12 inches or so. Thicker VB's help to prevent penetration during construction.

 

[KBVT]

For government projects, 10 mil minimum is required. 2 sheets of 6 mil is also common to protect against small tears.

 

[structuresguy]

We never use 6 mil. It just gets destroyed during construction by workers walking on it. 10mil is our minimum we use, when the floor finish is not critical, say bare concrete or carpet. Any time we have a critical floor finish, like wood floors (gyms) or epoxy or vinyl, we always spec 15mil Class A. The price difference between the is only pennies a square foot. But having a failing vapor retarder under a high end floor finish will cost your big time to repair. You decide how much risk you want to accept versus a few extra dollars.

 

[H57]

If it is exposed concrete and will stay exposed (shop area, storage, etc.) I do not specify a vapor barrier. I will also discuss with the client future use. If they intend to put on an epoxy coating in the future they should put in a vapor barrier now. I do not put a vapor barrier everywhere because that can be problematic in other ways.

For any other floor finish we use a minimum of 10 mil and go up from there depending on what the finish is. Gymnasiums have typically been the most stringent and I would concur with structuresguy in using 15 mil class A.

 

[abusementpark]

Thanks for the responses.

Does anyone know of any code requirements regarding vapor barriers?

 

[OHIOMatt]

Chapter 18 of the IBC covers this. You will have to read the verbiage, but I have had a number of building officials interpret the code to mean that a vapor barrier is required.

I have also found that vapor barriers are required under slabs by certain state energy codes. It has been a couple of years, but I think that the state of Oregon in one in particular.

 

[JAE]

I concur with H57, except I generally use 10 mil as the thickest for this kind of application.

 

[steellion]

10 mil, except for special applications.

 

[structuresguy]

I used to always use 10 mil for floors with high end finishes until I did a hangar a few years back. We had spec'd a 10mil Class A vapor retarder, which they did use one of our spec'd products. The hargar floors were finished in a very high end epoxy as they were "sales show rooms" as much as maintenance areas. But during construction of the hangar floors, the 10mil sheeting was still get chewed up quite badly, and this was over a sand bed, not gravel. The day before the pour, they had a crew go around and patch every hole and tear properly. But even while they were pouring, just from the concrete workers walking on it, new holes were forming. So they had a crew working just ahead of the concrete to patch any new holes as they formed. I personally watched every floor pour. This was one of the very few jobs I have worked on where the owner hired the EOR to provide full time on site representation. After seeing the 10mil barrier getting so many holes in it, and working on remedial solutions for a failing epoxy floor in a satellite processing facility for the Air Force, I always spec 15 mil now for anything with high end finishes just for the extra durability.