Construction Materials-Fluid Applied WRB/Liquid Flashings

When I first started in the construction industry, more than 20 years ago, adding water and air membranes and sealing the exterior of a home was in it’s infancy.  Sure, adding tar paper or felt to the exterior of a home had been around for many decades, but the use of Tyvek and Typar were fairly new and a lot of builders and homeowners were confused about how they worked.  (Some are still confused today.)  In todays blog, I am going to discuss a newer option in water resistant barriers (WRB).  Not only can fluid applied products be used for the entire exterior of the home, they can also be spot applied to help protect difficult to seal transitions, corners, or other hard to flash area.

Why install a whole house liquid applied WRB? The advantages are a superior product.  The liquid flashing is sprayed or rolled directly to the sheeting, usually oriented strand board or plywood.  All nail holes, material transitions, corners and seams are covered.  The liquid applied adheres directly to the surface it is applied to, won’t blow off in high winds if left exposed for a period of time.  The products main purpose is as the water resistive barrier but will also provide air sealing, often resulting in a passed blower door test without any additional air sealing needed.  The cost to install a liquid applied WRB is going to be more expensive than a traditional house wrap.  Labor costs with specialized training and higher product costs currently make fluid applied WRB’s less common.

How about a spot-applied liquid flashing?  I believe the spot application of a fluid applied or liquid flashing will become common on all new residential builds.  Future codes will require tighter and tighter assemblies.  Addressing these “difficult to air seal” transitions in corners, windows and doors, or dissimilar materials with fluid applied flashings are simplified over using tapes.  Try using a tape to seal between the concrete foundation and house wrap?  The liquid flashing also creates a water tight assembly.

Fluid applied membrane on Zip Sheeting.

In remodeling situations, some common building materials used in past decades are nearly impossible for tape to stick to.  Take fiberboard, commonly known in my area as buffalo board.  This fibrous sheeting will not hold a tape.  Liquid applied flashing, though not perfect, is the best option.

Do whole house fluid applied WRB’s have a perm rating?  In a northern climate, they have to, especially in Minnesota where the use of polyethylene sheeting on the warm in winter side of the building assembly is common.  The only drying potential is to the exterior.  Be sure to know the product to be used.  A fluid applied product designed for a southern climate may have a low or no perm rating.  A great choice for them, a bad choice for a cold climate.

A residential fluid applied whole house WRB product I am aware of for use in a northern climate is Tremco’s Enviro-Dri.  This WRB is required to be installed by a certified installer and the product has a perm rating of 13.  As far as liquid flashing go, there are many on the market.  I have personally used Zip’s Liquid Flash and will soon be using Henry’s Air-bloc LF liquid applied flashing.  Prosoco’s R-Guard Fast Flash is another popular choice.

Henry’s VP 100 WRB and Air-Bloc LF

As I said earlier, I believe liquid flashings used in spot applications for hard to seal and waterproof transitions will be common in the future, whereas whole house fluid applied WRB’s will be more common on the high end home market.  I will be posting the use of the Henry Air-Bloc LF liquid flashing (along with Henry’s VP 100 self adhering WRB) on my own home in a future blog posting…stay tuned.

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