What are weep holes and do I need them?

Posted on March 29, 2011

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Many homeowners first discover weep holes while observing the exterior brick veneer of their home. I get questions like these…Did the bricklayer forget to fill these holes in the bottom of my house? Can’t mice and insects enter thru these openings? Can you fill them in for me? [In the interest of full disclosure, addressing this whole problem is why I invented and partnered in the development of the BrickVent moisture control system.]


Karen Shaw

Photos:Karen Shaw                            Christian Meyn                                            Karen Shaw


Your bricklayer did NOT forget to put mortar in between some of the brick along the bottom of your house out of your brick wall. As a bricklayer myself, I will admit that while the typical mason tends to be a breed apart, large holes in brickwork are not something he is typically going to miss. No, those holes are there for a reason. Whether or not they are serving their intended purpose is another question.

Brick is in no way waterproof. As a matter of fact, because brick (and stone) is a porous material it actually behaves much like a sponge. During a rain event, the masonry wall  absorbs a tremendous amount of water and and stores it. The weep hole is designed for two purposes. 1. It provides an opening to allow water to drain out through the bottom of the wall. 2. It is intended to allow ventilating air to enter behind the wall to help dry the structure.

Weep holes do have some serious drawbacks though. Varying according to local codes, typically these 3/8” openings are spaced apart every 3rdor 4thbrick along the bottom of the wall. These openings are equivalent to a tiny sized welcome mat and open door. They are large enough to allow mice, roaches and other pests to enter the structure of the house. My next door neighbor called me over one day terrified. She had witnessed a snake slithering thru a weep hole in her house and wondered if I could get it out! In my best Dr. Leonard McCoy impersonation, I told her, “I’m sorry Lady, but I’m a bricklayer, not a herpetologist!” Seriously though, with these openings there is nothing standing in the way of all sorts of critters taking up residence in your home. Check out this cute video illustrating the problem on you tube: http://www.youtube.com/watch?v=-2m7Z0OvGX4

Another serious drawback of weep holes is the lack of adequate ventilation. Modern homes are built more air-tight than ever. In the past, moisture was allowed to move freely from the interior of the home to the exterior and vice versa. This allowed the structure to “breathe.” Modern homes have lost this ability and moisture that enters through the outer masonry wall can become trapped. This can lead to disastrous consequences such as mold, spalling and deterioration of the masonry structure itself. The home industry has attempted to address the problem through the installation of weep holes. The problem is that in relation to the overall size of a masonry wall these small opening cannot provide the ventilation needed. For an illustration of the problem click here: Brick Ventilation

Three things you can do… 1. You can install weep inserts into your existing weep holes. For more on weep inserts click here: Weep Inserts 2. If you are experience moisture problems in your home BrickVents can be installed along with the application of a siloxane water-proofer. This will help, if not solve, many moisture problems by keeping the majority of water out and allowing the wall to expel the rest through proper ventilation.  3. Before building a new home, explore the possibility of installing BrickVents for a low cost insurance against future moisture (or critter!) problems For more info visit: brickvent.net

By Ernie Alexander

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