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by • February 19, 2015 • Building Science, Exteriors - Siding, Stucco, Brick, Stone, Wood, Metal, Housewrap & WaterproofingComments (8)15248

Brick Veneer – Best Practice for Waterproofing behind

Question: What type of weather resistive barrier (WRB)should be used behind brick veneer?

Answer: When determining the proper WRB for behind a brick veneer the first thing to realize is that brick is not a waterproof product. In fact brick is highly porous and absorbs water readily, so it cannot and should not be depended on to stop moisture from entering a wall system.  (Brick is among many materials like stucco & stone that are considered Reservoir Claddings.  For more a more in depth discussion on Reservoir Claddings and Solar Drive see this article from Building Science Corporation.)

The second thing to realize is that brick gives up its moisture pretty readily. That means that it dries quickly to the outside under most conditions. The one exception is when the sun beats down on moisture laden brick. In this case solar driven moisture from the brick is pushed into the airspace behind the brick, and unless the proper WRB is in place, the wall sheathing on the other side of the air barrier can be at risk.

I recommend using a WRB with a perm rating lower than conventional house wrap. A lower perm rating means that the WRB is less likely to let moisture from the airspace behind the brick reach the wall sheathing. A product like Tyvek CommercialWrap has a perm rating of 23 to 28, as compared to regular Tyvek HomeWrap that has a perm rating of 58. The CommercialWrap makes a better choice for WRB behind a brick veneer. When I’m applying a WRB to sheathing before installing a brick veneer, I like to put on a layer of CommercialWrap and then cover that with a layer of 15 pound felt as added protection.

Commercial Tyvek is a great WRB behind Brick.

Commercial Tyvek is a great WRB behind Brick.

Notice the base wall flashing wrapped UNDER the Tyvek and on top of the brick ledge.

Notice the base wall flashing wrapped UNDER the Tyvek and on top of the brick ledge.

I also do most of my work in the hot humid south. In these parts peel-and-stick membrane can be also used as a WRB behind brick veneer. These membranes typically have a perm rating less than one. An important caveat for this application is making certain that you do not have an additional vapor barrier inside the walls of the house, which can trap moisture and cause damage inside the walls.  This advice is mainly for buildings in the South and for buildings with more exposure such as this commercial building with no overhang.  

Commercial Building with Brick Veneer & CCW 705 Peel & Stick WRB

Commercial Building with Brick Veneer & CCW 705 Peel & Stick WRB

This detail works in the hot/humid South where we dry to the inside.

This detail works in the hot/humid South where we dry to the inside.

Drainage detailing with brick veneer is just as important as the type of WRB material that you choose. All penetrations such as windows and doors should have through-wall flashing that is integrated into the drainage plane at the sheathing. Through-wall flashing should also be used at the base of the wall along with weep holes to let any accumulated moisture drain away safely. And finally I always install mortar net at the bottom of the air space. This mesh product is designed to catch and trap an mortar that falls while the brick veneer  is being constructed to keep the weep holes free of debris.

Mortar Net catches the droppings in the air gap and ensures the bottom of the wall stays unclogged.

Mortar Net catches the droppings in the air gap and ensures the bottom of the wall stays unclogged.

(Image From MortarNet.com)  This shows how the keystone shape keeps the bottom weeps clear for air flow and drainage.

(Image From MortarNet.com) This shows how the keystone shape keeps the bottom weeps clear for air flow and drainage.

I hope this has been helpful!

Best,

Matt Risinger – Risinger Homes in Austin, TX

Visit my Blog at www.MattRisinger.com

Risinger Homes is a custom builder and whole house remodeling contractor that specializes in Architect driven and fine craftsmanship work. We utilize an in-house carpentry staff and the latest building science research to build dramatically more efficient, healthy and durable homes.

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  • Ben Chase

    Up here in Amarillo, new construction is almost exclusively brick with Zip System sheathing. At 12-16 perms, Zip System seems like it would work well if you follow your Zip Wall Tips & Advice, like the base wall flashing, etc. Do you see any issues with using brick veneer -> air gap -> 2″ EPS -> Zip System?

    • Ben, I’ve not used Zip with Exterior Insulation. I might coach you to add a strip of Zip tape verically every 16-24″ to create a drainage plane behind the Foam. I would expect this detail to work in your climate zone. Be sure to detail your penetrations in an air-tight manner like QuickFlash. Best, Matt

  • Niaga Artha Chemcons

    the article its very interesting, please read to our web on http://www.ahlibeton.co.id/2015/09/waterproofing-membrane-bakar.html

  • Neo Stefanides

    I am doing a new construction with thin veneer stone in New York……Water front (sound) on long island….My contractor wants to use 30 lb tar paper….what is your opinion of tar paper vs tyvec

  • Heath Bragg

    Having trouble finding flashing for brick ledge. Is 6 mil plastic acceptable. Can not find anyone in my area that has heavy vinyl. Also where do you get mortor net? Thanks!

    • Don’t use the 6mil plastic as a flashing. Not durable enough. Use a 40mil peel&stick membrane similar to an ice/water shield you would use on your roof. Here’s an example: http://amzn.to/2h2PUyH OR, have a piece of sheet metal bent. You can get the mortar net at any masonry supply house. In Austin TX I buy from MPI. Best,Matt

  • Your information is very informative. Have you suffer from the brick veneer. If yes take the advice from professionals.