Vapor barrier thickness is a key attribute of a below-slab vapor barrier but it does not tell the whole story. Tune into this Stego IQ episode where Stego Technical Director Dan Marks provides some insight on all the key attributes that make up a high-performing under-slab vapor barrier which is puncture resistance, tensile strength, and most importantly permeance and longevity.
Does thickness tell the whole story about a vapor barrier? This is Stego IQ.
Specifying thickness for a vapor retarder is like specifying the size of a car to determine its performance. We want to know what's under the hood! Thickness is a decent indicator of general performance, but it doesn't give us specifics that we want and that we need to have for the performance of the product.
We want to know the engine -- and the engine for the vapor retarder or barrier is going to be its puncture resistance, its tensile strength, and -- most importantly -- its permeance and longevity.
6-mil is an absolute minimum for the general residential building code, but for many years the Committee 302 of the American Concrete Institute (ACI) has recommended; "...that the thickness of the vapor retarder be no less that 10 mils (0.25mm)." In their most recent; "Guide to Concrete Floor and Slab Construction (ACI 302.1R-15)" Comittee 302 now recommends that the thickness and permeance of the vapor retarder material be selected on the basis of the protective needs of the materials being applied to the slab surface or the environment being protected, and the durability needed during and after installation.
With all that said, specification should not begin and end by meeting a minimum thickness. We also want to make sure the metrics and the performance match what we're trying to achieve. In this case: long-term water vapor protection.
We want to make sure that the permeance rating is low enough that our floor coverings, stored goods and indoor air quality are not adversely affected. We want to make sure that the product is going to maintain these characteristics -- specifically the permeance rating -- for as long as we need it to.
And yes, we want to make sure that the material is durable enough to be installed effectively in the first place, and can withstand the potential construction traffic.
Again, thickness is not necessarily the criterion were concerned about. We want to make sure the metrics and the performance match what we need.
Keep learning: build your brain and your knowledge. You can view more educational videos on Stego IQ topics on stegoindustries.com.
Installation, Warranty and State Approval Information | Privacy Policy | Intellectual Property Notice