Vapour Barrier necessary?

[Dedthings]

Hey Guys, I have been gathering a lot of information from this site, and absolutely love it. This is my first post, probably of many. I am starting my first garage, ever. I am super excited and nervous at the same time.
My question is about vapour barrier. I plan on doing an epoxy finish and have read that I will need a VB. I have 14" of crushed gravel as my base, which doesn't seem to stay too wet. It is the 11th hour and need to know soon, if I should do the VB anyway. Also, would a hockey rink liner work, it is darn near puncture proof. Thanks.

 

[kenfain]

Definitely use a vb

 

[benwah]

The necessity of a vapor barrier is determined by the moisture vapor transmissions through your concrete. Typically, Moisture Vapor Transmission should not exceed three lbs per 1,000 sq ft in a 24 hour period for an epoxy coating. Each manufacturer will probably have their own requirements.

There are a couple ways to determine your MVT levels.

The generic way is to duct tape a 12x12" sheet of plastic down and check it 24 hours later.

This will simply let you know that you have moisture issue, if wet.

To know exactly what your moisture levels are, you need to perform a calcium chloride test (Reference ASTM F 1869 "Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride.")

Some may say that is "too extreme" or "not needed" or "a waste of money". I do not care, this is the proper way to determine moisture levels. Also, it is much cheaper than installing an epoxy floor then having it fail because of moisture issues. If you think you have issues, do the first test. If it comes back with water on the plastic I would perform a few of the Calcium Chloride tests.

EDIT: I may have misunderstood.. Are you are talking about a VB before you pour concrete? If so, then yeah, do it.

 

[Chris705]

Hockey rink liner sounds like it would be similar to Stego Industries 15mil vapor barrier. Really heavy duty, use it if you have it.

 

[ConCretin]

If you are going to install epoxy or any other floor covering, you should install a vapor barrier. Period. The enemy of your epoxy floor is water vapor, which you can't detect by looking at the sub grade material.

I'd use a 15 mil product such as Stegowrap. Compared to traditional polyethylene sheeting, a specialized membrane will have lower permeance, be more resistant to damage and will hold up longer. Compatible tape, caulking and putty are available to seal up seams and penetrations, which is vital.

If your going to invest in an expensive epoxy floor, a properly installed under slab vapor barrier is cheap insurance.

 

[LegacyIndustrial]

Llwillysfan nailed it!!

 

[Chuck]

Yes. You'll probably spend more on the epoxy than the VB anyway - saving pennies on VB is likely to cost many dollars in headaches later.