Facts It's Important To Be Familiar With Concrete Vapor Barrier

· 3 min read
Facts It's Important To Be Familiar With Concrete Vapor Barrier




Exactly what is a concrete vapor barrier?
A concrete vapor barrier is any material that stops moisture from entering a layer of concrete. Vapor barriers are widely-used because while fresh concrete flows wet, it’s not designed to stay like that. It must dry then stay dry to avoid flooring problems.




If you’ve ever endured a problem with a basement floor (or any concrete floor), you already know the type of damage that as well much moisture could cause. Moisture enters concrete in several ways, including via the ground, from humidity up, and thru leaky plumbing that passes through a slab. Needless to say, there’s also the moisture that's from the original concrete mixture.

There’s only one-way moisture leaves concrete, though, and that’s via its surface. When you have a concrete floor that’s in continuous connection with an origin of moisture, you’re gonna have problems. This is why a vapor barrier under concrete is vital. Vapor barriers are a way to maintain moisture from getting yourself into the concrete.

Note: A vapor barrier is not just like an underlayment. However, there are underlayments that behave as vapor barriers.

Vapor barrier permeability is expressed in perms.
Vapor barriers have varying examples of permeability, expressed in perms. The larger the number, the more permeable the material. Impermeable vapor barriers are those with a rating of 0.1 perm or fewer while class II vapor retarders are those with a rating more than 0.1 perm and less than 1.0 perm.

You’ll hear people while using the terms ‘vapor barrier’ and ‘vapor retarder’ interchangeably. However, strictly speaking, they aren’t a similar thing. Vapor barriers are less permeable than vapor retarders. In this post, we'll be using the term ‘vapor barrier’.

Why's too much moisture in concrete a difficulty?
A word: adhesives. Too much moisture in concrete is a concern as it may cause pH changes that destroy adhesives. Here’s what are the results.

As moisture makes its way to the outer lining of the concrete slab, soluble alkalies appear for your ride and raise its surface pH above those of flooring adhesives. This leads to the adhesives to breakdown so you get flooring failures for example swelling, bulging, or cupping.

Do you want a vapor barrier under a concrete slab?
In a word, yes. Here’s why.

There’s almost always water underneath a building site. It might not be at the surface, but that doesn’t mean it’s not there. This water can progress from the soil and are avalable into connection with the bottom of a concrete floor via capillary action. Capillary action might be stopped by using something known as a capillary break, a layer of crushed rock that goes involving the subgrade along with the slab.

Capillary breaks do a sufficient job of stopping water in its liquid state from reaching a slab. However, they can’t stop water in vapor form from reaching and entering a concrete slab. Therefore, there must be something within the slab that stops vapor moisture from entering.

You might also need a vapor barrier for liability reasons since most manufacturers of flooring include vapor barriers or retarders in their installation guidelines.

How thick should a plastic vapor barrier be?
In line with the Help guide Concrete Floor and Slab Construction authored by the American Concrete Institute, a vapor retarder really should not be less than 10 mils thick. You may want a good thicker barrier though if you’re covering material with sharp angles.

Net profit: Vapor barriers need to be sufficiently strong enough so they really don’t easily puncture. When they do, moisture is certain to get in and that’s what you’re continuing to keep out.


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