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Weep holes in brick walls: this article explains the purpose of drainage openings & rain screens in solid brick walls and in some brick veneer walls: brick wall weep holes and recommends their use in new construction and in some brick wall repairs or retrofits. Weep holes in building exterior masonry walls (brick or stone) are a drainage system that is used in cavity wall or rain-screen wall construction methods to get rid of water that has penetrated the outer wall skin or surface. We explain how these weep or vent openings in brick walls work, where and how they should be installed, and what special products such as opening screens & flashings are available.
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Watch out: Both structural brick walls and veneer brick (or stone) walls may be designed either as a barrier wall or a cavity/rain-screen wall. Before you can evaluate the condition of a wall you need to understand how it was built. Our page top sketch, courtesy of Carson Dunlop Associates, shows both the reasons for and the typical design details used in weep openings on brick walls.
The beautiful Flemish-bond structural brick wall (left) on the Vassar College Campus was constructed with very subtle drain or weep openings at the wall bottom. It has survived intact even though the building is located in a seasonally wet and freezing climate.
To diagnose a building water entry or moisture problem originating at its exterior walls we must first understand the construction concepts that were used to build that wall: two very different concepts apply, though they often appear mixed or even confused in buildings: barrier wall construction methods (the wall exterior skin keeps out water) and cavity or rain-screen wall construction (the wall is designed to handle and get rid of water that penetrates the outer skin). See WALL CONSTRUCTION BARRIER vs CAVITY for definitions and explanations of barrier wall construction compared with cavity / rain screen exterior wall construction methods, objectives, and damage vulnerabilities.
Definition & Images of Veneer Wall or Masonry Wall Weep Openings
Weep openings are drainage holes left in the face of a brick veneer wall [and possibly some other constructions] in order to allow water that has penetrated the wall to escape downwards through the wall cavity and out to the exterior of the wall surface through the weep openings.
This escape passage and wall design are a method for reducing water intrusion into the structure interior. According to the Masonry Design Manual, weep holes are
At left we illustrate the most basic brick wall weep opening.
At below left we show a brick wall (a veneer in this case) with weep openings at regular intervals at two heights above ground level. Below right is a closeup of one of the drainage openings. Veneer wall weep openings are placed at least at the very bottom of the brick veneer wall cavity. We suspect that the wall cavity does not extend lower than the weep holes in our photo - why? The lower brick courses were probably laid tight, with no cavity at all, against a solid concrete or masonry block foundation wall.
Not All Brick Veneers Lacking Drainage are Damaged - Some of these are Barrier Walls not Cavity / Rain Screen Walls
At left we illustrate a double-fault at a brick veneer wall weep hole found on a New York Home. This "Do-it-yourself" excuse for veneer wall drainage is too small, placed above the level of the wall base flashing, and is completely clogged. All of the weep holes we found in this wall were in the same condition.
Faux Bond Courses May Confuse the Identification of a Brick Veneer Wall - but is it a problem? Not Necessarily.
The brick walls of the New York home in our photo at below left contain no weep openings. Bricks were laid tight against a solid masonry block wall with "faux" bond courses to the left of the chimney and all stretcher brick courses to the right of the chimney.
Walls both left and right of the chimney were constructed with no drainage. Bricks were mortared against the masonry block structural walls of the home with no air space and no drainage provision.
This is a brick veneer on block structure approximately 30 years old. While the mason omitted weep openings, we did not find any evidence of water or frost damage to the brick veneer except at another wall where splash-up from roof spillage had worn mortar joints. This is a barrier wall design, not a cavity / rain-screen wall designed structure.
Traditional structural brick walls such as at the building shown at above left are comprised of two or more wythes [defined below] of brick laid in parallel and reinforced by bond courses at regular intervals. Such walls typically include an air gap between the exterior wythes of brick - the wall outside surface, and the wall interior. At above right the mason actually built a brick veneer wall over solid masonry block.
That space allowed water that leaked into the wall to run down the wall interior and drain at the wall bottom - provided that the wall bottom included weep openings or drainage. At BRICK FOUNDATIONS & WALLS we describe the collapse of the structural brick walled building shown at right.
Definition of wythe or brick wythe
If you look at a brick masonry wall, one brick thickness of the wall is one wythe. A brick veneer wall constructed using full-dimension bricks will be one brick wythe in thickness (of the veneer). The total wall thickness will include the veneer wythe plus the thickness of the wall structure itself.
A structural brick wall is normally two or more wythes of brick in thickness, usually separated by an air space of about an inch to form a thicker, more dry wall. In the cross section of the collapsing brick structural wall at above right you can see multiple wythes of brick. More brick and brick wall definitions and details are at BRICK VENEER WALL Loose, Bulged.
How are brick veneer walls usually supported?
Carson Dunlop Associates sketch (blelow) illustrates the usual manner in which a brick veneer wall is supported.
On occasion we find an "add-on" brick veneer supported by a steel lintel bolted to the building structural wall bottom.
Details about brick veneer wall support, bulge & damage, fasteners, and repairs for attached veneers on wood frame construction are found at BRICK VENEER WALL Loose, Bulged.
Where do the brick wall weep holes go? At the wall bottom, but above ground level.
Carson Dunlop Associates sketch (below) illustrates that it's a bad idea to backfill against a building so that the wall's weep openings are below grade.
This mistake traps water inside the wall inviting frost damage, building water entry, and insect attack on the building sills and floor framing.
Tom Tamlyn, a residential building products manufacturer, sent us the two plastic weep hole covers shown below.
At below left we show a brick wall weep hole cover intended for new construction. The openings are intended to keep critters out of the veneer wall; At below right we show the same device from the back so that you can see its construction.
At far left is a similar weep hole cover intended for retrofit use in existing brick walls or brick veneer walls. We include the new-construction weep opening cover at right so that you can see the difference in how these products are constructed.
Other masonry product manufacturers (such as Airolite® and Brickvent™) provide a larger vent openings by replacing entire bricks along the wall bottom to provide improved wall drainage and moisture ventilation, especially if combined with wall top moisture vents described below.
Watch out: several errors or omissions in a brick wall drainage or venting system can contribute to building moisture, water entry, and damage to both structural brick and veneer brick walls, including:
In addition to providing weep openings to permit moisture or water drainage out of brick veneer walls and some structural brick walls, modern construction practices may include a more effective means of moisture removal from an attached veneer wall used in wood frame construction: vent openings are provided at the top of the wall before the brick veneer wall is constructed against the building.
These wall top openings behind the brick veneer vent into the building's attic or roof space to permit moisture to escape from behind the veneer. Air entering through vents at the bottom of the veneer wall flows upwards behind the brick veneer, passing through openings at the wall top into the attic or roof space where it is vented outdoors through a ridge vent or other roof venting system..
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Frequently Asked Questions (FAQs) About Weep Holes & Drainage in Brick Walls
Question: Where can I buy weep inserts?
Hi I'm like to know where I can buy weep inserts for the bricks around my house. - J.S.
Several manufacturers provide brick wall weep hole systems that assure that moisture or water behind the brick wall or brick veneer can drain out of the wall while at the same time insects or larger critters are kept from entering the walls. We describe Tamlyn brick wall weep opening inserts used in new wall construction and a second product used in retrofits at Guide to Brick Wall Drainage Opening, Flashing & Ventilation Products.
Here are some brick wall weep insert product sources:
Questions & answers or comments about the requirements for drainage in brick walls, both structural brick & brick veneers..
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