Moisture Barriers vs. Waterproofing Membranes

With all of the products on the market today that offer moisture control in some way, selecting the correct product for the job is not always an obvious choice. When choosing these types of products, certain questions arise: What exactly are waterproofing membranes and moisture-reduction barriers? What is each made of? Why would I pick one over another? The short of it is that it will vary a bit from job-to-job, but here are some general details to keep in mind:

What is a Waterproofing Membrane vs. a Moisture Barrier?

Waterproofing is just that, it stops liquid water from moving from one space to another; it does not stop water in a vapor form completely (though it can slow it down). Waterproofing and moisture barriers are completely different products with different jobs. You would use a waterproofing membrane to contain water in a certain area, like a shower pan for example. 

Moisture-reduction barriers control moisture in a vapor state. These membranes fill the pores of the substrate, typically with epoxy or a polymer, and keep virtually all vapors from passing through within the specific products limits. These types of products are well-suited for treating high-moisture slabs, or where a concern of high moisture conditions in the future exists.

What are the differences in composition of the products?

Waterproofing membranes are typically a liquid-rubber type material that is applied similar to traditional wall paint. Mapelastic AquaDefense for example, is rolled onto the substrate with a 3/8” nap paint roller in two coats. There are other types that require reinforcing fabrics and meshes or application with a trowel vs. a roller; though roller-applied membranes are most common. There are also cement-based waterproofing membranes like our Mapelastic 315, which is a cement powder that is mixed with a supremely flexible additive, and is then trowel-applied in conjunction with a reinforcing fiberglass mesh for added strength. 

Moisture-Reduction Membranes can vary in composition quite a bit, but the three most popular types MAPEI manufactures are epoxy, polyurethane, and polymer-based. First, epoxy (the most popular choice) does a phenomenal job of filling open concrete pores and making a monolithic membrane to guard against vapor transmission. Epoxies can be a touch difficult to work with, and most of these types of membranes will have moisture vapor emission limits. This brings us to products like our Planiseal PMB, which is polyurethane. Polyurethanes like Planiseal PMB can be applied easily using a paint roller, and are already pre-mixed saving time and frustration. Some of these products have moisture limits, but Planiseal PMB does not (so long as the slab has no standing water on it). Finally, polymer-based moisture-reduction membranes like our Planiseal MSP are inexpensive, easy to apply, and are typically very available in the marketplace. These products fill a great niche, but do not have incredibly high moisture limits.

So, how do you choose? Decide if you need to stop “water” or “Water Vapor”. If you need to stop water from moving to one area to another, like creating a basin to keep water in a fountain, you need a waterproofing membrane. If you are dealing with a high moisture concrete slab, and need to install solid sheet vinyl, then a moisture-reduction barrier would be the ideal choice.

Check the Technical Data Sheet. So you decided on the type of product needed, and now you need to select the appropriate membrane; get over to MAPEI.com and pull up the technical data sheets for the products in that category. The concrete slab is measuring 20 lbs. MVER, and the final floor is going to be engineered wood? Check the data sheets for the limits and uses on each product, and call us if you get stuck!

Whether you need moisture control, waterproofing, or anything else along the way in the flooring installation process, we are here to help. Just pick up the phone and call us at 1-800-992-6273, click here to drop us an email!