It has been said that water is the enemy of architecture. Water will do everything it can to penetrate your building’s exterior and wreak havoc on the interior. Rest assured, water will move up, down, sideways, diagonally, or any other direction it needs to in order to compromise your building. So, how do you keep water outside of your buildings where it belongs?
Meet Your New Best Friend: Water Resistive Barriers
Water resistive barriers are synthetic sheet products that are installed in exterior wall systems to help control air infiltration and divert water out of the exterior wall. Fluid applied air barriers are another type of barrier system that performs similarly to water resistive barriers. They are designed to function like a water resistive barrier, however they have the added feature to control varying levels of water vapor transmission from outside the building to its interior, or vice versa.
This article will focus on sheet products that address water and air infiltration movement within the exterior wall assembly. This type of barrier is commonly referred to as a Water Resistive Barrier (WRB). Tyvek and GreenGuard MAX Building Wrap are two examples of WRBs. WRBs are typically sheet materials mechanically fastened to the outside face of the exterior wall sheathing. Their primary function is to back up the outermost veneer layer (i.e., brick, stone, metal panel, wood, etc.) and serve as a protector of all the other materials used to construct the exterior wall such as the sheathing, wall framing, insulation and drywall.
WRBs are applied to the sheathing system as large, unrolled sheets. You can tell when they’ve been installed because the building looks like it has been wrapped like a present, but the final outermost layer of the building exterior hasn’t been applied yet. WRBs are a critical component of exterior wall systems because water will travel through porous brick and mortar as well as through the joints of wood and metal wall panels. When installed properly per manufacturer recommendations, the WRB will divert water back to where it came from and prevent air from penetrating any further into the building.
Getting It Right the First Time
Before a WRB is installed, it’s important that the architect and general contractor meet and discuss how the WRB will be installed and coordinate any other trades whose work will interact directly with the WRB. This meeting should cover all the potential detailing and construction issues related to the WRB, from actual product specification to construction sequencing.
Once application of the WRB begins, the design and construction administration team should be paying special attention to its installation and detailing on-site. It’s important that they are actively investigating the condition, penetrations, and installation of the WRB, because any oversight in construction is a potential weak point—and water loves to find those weak points!
Before the WRB is covered up with the final layer of exterior wall materials (brick, stone, metal panel, wood, etc.), the design team should perform a punch. Where a higher level of quality control is desired, commissioning of the WRB system in addition to a punch list can also be performed. A punch is essentially a very detailed and thorough visual inspection of the condition of the WRB system and is performed by the design or construction administration team. This includes a list of corrective action items to address any issues or defects in construction or application that should be fixed before exterior veneer materials start to get applied. Commissioning involves water testing and blower door testing by an independent authority (not the designer or constructor) to make sure that the WRB performs as designed by the manufacturer.
A punch list is usually built into the project design or construction administration fee, while commissioning is often an additional expense. Both the punch and commissioning are efforts to make sure that the WRB is as perfect as possible before it is covered up by the final exterior material forever. Fixing a problem after that final exterior layer has been applied is incredibly costly and time consuming. In addition to the punch or commissioning, it’s a great idea to get the WRB product representative on-site to get his or her expert opinion on the installation.
Speak Now or Forever Hold Your Bucket
Remember that water wants to ruin your building! Figuring out where and how water is getting into your building after construction is complete is incredibly difficult and potentially expensive. That’s why it is critical to make sure that a WRB is effectively designed, detailed, and constructed in your next building project. If you aren’t sure how your WRB is being designed or constructed, ask. If your design and construction team doesn’t have a very detailed and thorough response, well, let’s just say you might want to invest in some buckets!
For more information or to talk about a specific issue you might be facing, please email Bob Sanderson or call 260-422-4241.