Waterproofing membranes versus moisture-reduction membranes

With all 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 membranes? 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 versus a moisture-reduction membrane?

• Waterproofing and moisture-reduction membranes are completely different products with different jobs. Waterproofing membranes stop liquid water from moving from one space to another, but they do not stop water in a vapor form completely (though they can slow it down). You would use a waterproofing membrane, such as a shower pan, to contain water in a certain area.
• Moisture-reduction membranes 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 for where a concern of high-moisture conditions in the future exists.

What are the differences regarding the composition of these membranes?

• A waterproofing membrane is typically a liquid-rubber-type material that is applied in a way that is similar to traditional wall paint. Mapelastic AquaDefense, for example, is rolled onto the substrate with a 3/8" (10-mm) nap roller in two coats. There are other types that require reinforcing fabrics and meshes or application with a trowel versus a roller, though roller-applied membranes are most common. There are also cement-based waterproofing membranes, such as our Mapelastic 315, which is a cement powder that is mixed with a supremely flexible additive and 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 that MAPEI manufactures are epoxy, polyurethane and polymer-based. Epoxy (the most popular choice) does a phenomenal job of filling open concrete pores and making a monolithic membrane to guard against vapor transmission. Planiseal VS  and Planiseal VS Fast are our two epoxy moisture-reduction membranes. Planiseal VS Fast has reduced drying time that allows the project to turn around much quicker. Epoxies can be a touch difficult to work with, and most of these types of membranes will have some moisture-vapor-emission limits. The good news is that Planiseal VS and Planiseal VS Fast do not have any moisture-vapor-emission limits, providing that there is no standing water on the slab. This brings us to products such as our Planiseal PMB, which is a polyurethane moisture-reduction membrane. Polyurethane moisture-reduction membranes such as Planiseal PMB can be applied easily using a paint roller and are already premixed, 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 such as 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, such as 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, wood or laminate, then a moisture-reduction membrane would be the ideal choice.

Now that you have decided on the type of product that is needed, it is time to select the appropriate membrane. Get over to www.mapei.com and pull up the Technical Data Sheets (TDSs) for the products in that category. The concrete slab is measuring 20 lbs. (9.07 kg) moisture vapor emission rate (MVER) and the final floor is going to be engineered wood? Check the TDSs 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 or click over to www.mapei.com to drop us an e-mail!