Basement Vapor Barrier

Terms of Basement Waterproofing - Vapor Barrier

Jacob Ewing Lee

There's been much confusion in the home improvement industry with terminology. In the basement waterproofing industry there is one objective: keep the water out. The technology needed in the basement to do this is similar, however, different from the technology used in construction for the rest of the home.

A term that's thrown around a lot is Vapor Barrier. But many people confuse what a true Vapor Barrier is with a Vapor Diffuser.

Vapor Diffuser: Pretty much anything that can be put up is a vapor diffuser (including plywood and vinyl siding). It slows down moisture transfer from the outside to the inside. Typically traditional plastic sheeted vapor diffusers are put up on the outside of home walls when building. These protect insulation and interior joists and crossbeams from the elements that penetrate your siding. Vapor diffusers are only suggested for above grade construction because they're not designed for 100% moisture defense. Perms, or the rate at which water vapor can move through an object, on Vapor Diffusers normally range anywhere from a 1(which means little to no protection) to a .4 (which is better, but not enough to "waterproof" with).

Vapor Barriers: Vapor Barriers are different because they are specifically designed with better Perm rates. A typical Vapor Barrier that's used in basement waterproofing can range anywhere from a .014-.0015 (which is an amazing number! The lower the number the better protection you get!). This means that a barrier is stronger in defending against water vapor transfer. They're even so strong that the typical way of installing them has to be different when finishing. Vapor Barriers need to be attached to the foundation wall and directed to a drain system otherwise the water ends up on your floor, which defeats the whole purpose of waterproofing in the first place. 1"-2" from there studs can be built and insulation can be installed.

Far too often I have seen finishing contractors put vapor diffusers in basements to "stop water". Another problem that I see is that some of these same contractors install in front of the insulation. This can cause major issues when flooding occurs. Water can be trapped behind these diffusers (because they're okay for liquids, not vapor) and render all the insulation useless and ruin your studs. This is the exact reason for why a Vapor Barrier has to be installed differently in a basement.

So, what have we learned? We've learned that Diffusers are for the upstairs and Barriers are for the downstairs. Barriers have a better perm rate, which makes them better at keeping all forms of water out, and they need to be installed differently if you plan on finishing off your basement space.

Jacob Lee- Pioneer Basement Learn more about basement waterproofing, finishing and design at Jacob's Blog:

http://www.diyguyct.blogspot.com

Basement Vapor Barrier

basement vapor barrier