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 Weep Holes, Drainage & Moisture Ventilation in Brick Walls
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InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
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.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
Weep Holes in Structural Brick & Brick Veneer Walls
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.
Readers of the article series BRICK FOUNDATIONS & WALLS should see these detailed articles on brick veneer walls and brick structural walls: BRICK STRUCTURAL WALL Loose Bulged and BRICK VENEER WALL Loose, Bulged and BRICK WALL DRAINAGE WEEP HOLES and also BRICK WALL THERMAL EXPANSION CRACKS. Also see this close companion article: FOUNDATION CRACK EVALUATION which discusses in detail the process of evaluating foundation cracks and signs of foundation damage by examining the crack size, shape, pattern, and location. And see BRICK VENEER WALL AIR LEAKS. For stone wall or stone veneer wall construction, diagnosis, repair advice see STONE FOUNDATIONS and STONE VENEER WALLS
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
Openings placed in mortar joints of facing materials at the level of flashing, to permit the escape of moisture, or openings in retaining walls to permit water to escape.
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.
Damaged Brick Veneer Walls - No Provision for Weep Openings
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 right 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.
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
- Each continuous vertical section of masonry one unit in thickness
- The thickness of masonry separating flues in a chimney - Masonry Design Manual
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 (far left) 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 Drainage Openings (Weep holes) Belong?
Where do the brick wall weep holes go? At the wall bottom, but above ground level.
Carson Dunlop Associates sketch (left) 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.
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Guide to Brick Wall Drainage Opening, Flashing & Ventilation Products
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.
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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:
- Missing weep openings: In traditional brick walls, omission of weep openings entirely, especially when wall materials or masonry admit wind-blown rain or leaks from roof spillage run down the wall. Similar problems may occur in stone masonry and particularly stone veneer walls. Vent openings in a veneer wall are typically placed 24-inches on center.
- Excessive trash mortar falling behind the brick veneer or inside of a structural brick wall cavity can block wall bottom vents, preventing proper wall drainage.
- Omission of wall bottom flashing to direct water out of the wall at the wall bottom risk building water entry, frost damage, and where wood sills are nearby, rot or insect damage
- Omission of veneer wall top vents to permit moisture to escape (see below)
- Omission of an effective moisture barrier or vapor barrier behind the brick wall
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Brick Veneer Wall Through-Ventilation - Airflow Removes Moisture
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.
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.
Reply:
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:
- Airolite BVC Brick Vents (extruded aluminum), The Airolite Company, LLC, PO Box 410, Schofield WI 54476, TelP 715-841-8757. Website: http://www.airolite.com/
- Brickvent™, Masonry Innovations, Masonry Innovations, 36 Woodview Drive, Pittsboro, IN 46167, Tel: 317.341.0882 or 317.695.0509, Email: info@masonryinnovations.com - the company provides this BrickVent™ moisture control system instruction sheet. , Website: http://masonryinnovations.com/
- Tamlyn building products, Tom Tamlyn, President, 13623 Pike Rd., Stafford TX 77477, Tel: 800-334-1676. Website: http://www.tamlyn.com
- Hohmann & Barnard, Inc, produces a huge range of structural ties and anchors, including for masonry repair and restoration, stone anchors, rebar ositioners, [Wing Nut 2-Seal™ Tie, wing nut veneer anchor seals air barriers], Offices in 8 U.S. cities, including H&B New York
30 Rasons Court,
Hauppauge, NY 11788
(P) 631-234-0600,
(F) 631-234-0683,
Toll: 800-645-0616, Website: www.h-b.com
- Other brick wall drainage product manufacturers are welcome to CONTACT us to be listed here. No fees are involved. InspectAPedia.com has no business nor financial connection with any manufacturer or service provider discussed at our website.
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
- [1] Williams, M.F., Williams B.L., "Water Intrusion in Barrier and Cavity / Rain Screen Walls", Water in Exterior Building Walls: Problems and Solutions, ASTM STP 1107, Thomas A. Schwartz, Eds., American Society for Testing and Materials, ASHRAE, Philadelphia, 1991, retrieved 8/10/12, Abstract:
Exterior walls are designed and constructed using barrier or cavity / rain screen wall principles. Exterior Insulation and Finish Systems (EIFS) are typically constructed as barrier walls; masonry is often constructed as a cavity wall. These wall systems are discussed along with common deficiencies that allow water intrusion to occur.
[Mark F. Williams and Barbara Lamp Williams are president and vice president respectively of Kenny/Williams/Williams, Inc., a building diagnostics firm at 945 Tennis Ave., Maple Glen PA 19002.]
- Airolite BVC Brick Vents (extruded aluminum), The Airolite Company, LLC, PO Box 410, Schofield WI 54476, TelP 715-841-8757.
- Brick Development Association, The Building Centre, 26 Store Street, London, WC1E 7BT, England, U.K., Tel: 020 7323 7030, Email: brick@brick.org.uk
- Brick Industry Association, 1850 Centennial Park Drive, Suite 301, Reston, VA 20191
Phone: 703.620.0010 Fax: 703.620.3928.
- Brickvent™, Masonry Innovations, Masonry Innovations, 36 Woodview Drive, Pittsboro, IN 46167, Tel: 317.341.0882 or 317.695.0509, Email: info@masonryinnovations.com - the company provides this BrickVent™ moisture control system instruction sheet. Web Search 02/16/2011, original source: http://masonryinnovations.com/Instruction_Sheet.pdf
- Canada Masonry Centre, 360 Superior Blvd., Mississauga ON Canada L5T 2N7. Tel: (905) 564-6622. Offers the CMCA Textbook of Canadian Masonry.
 Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides:
- Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
- Home Inspection Education Courses including home study & live classes at eleven colleges & universities.
- Home Inspection Education Home Study Courses - ASHI@Home Training 10-course program.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference Book, a reference & inspection report product for building owners & inspectors.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones.
Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.
- The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors.
Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
- The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones.
- Masonry Design Manual, James E. Amrhein & Walter L. Dickey, Civil & Structural Engineers, Masonry Industry Advancement Committee, Masonry Institute of America, ASIN B0006XMFZE
- Tamlyn building products, Tom Tamlyn, President, 13623 Pike Rd., Stafford TX 77477, Tel: 800-334-1676.
- "Concrete Slab Finishes and the Use of the F-number System", Matthew Stuart, P.E., S.E., F.ASCE, online course at www.pdhonline.org/courses/s130/s130.htm
- Sal Alfano - Editor, Journal of Light Construction*
- Thanks to Alan Carson, Carson Dunlop, Associates, Toronto, for technical critique and some of the foundation inspection photographs cited in these articles
- Terry Carson - ASHI
- Mark Cramer - ASHI
- JD Grewell, ASHI
- Duncan Hannay - ASHI, P.E. *
- Bob Klewitz, M.S.C.E., P.E. - ASHI
- Ken Kruger, P.E., AIA - ASHI
- Aaron Kuertz aaronk@appliedtechnologies.com, with Applied Technologies regarding polyurethane foam sealant as other foundation crack repair product - 05/30/2007
- Bob Peterson, Magnum Piering - 800-771-7437 - FL*
- Arlene Puentes, ASHI, October Home Inspections - (845) 216-7833 - Kingston NY
- Greg Robi, Magnum Piering - 800-822-7437 - National*
- Dave Rathbun, P.E. - Geotech Engineering - 904-622-2424 FL*
- Ed Seaquist, P.E., SIE Assoc. - 301-269-1450 - National
- Dave Wickersheimer, P.E. R.A. - IL, professor, school of structures division, UIUC - University of Illinois at Urbana-Champaign School of Architecture. Professor Wickersheimer specializes in structural failure investigation and repair for wood and masonry construction. * Mr. Wickersheimer's engineering consulting service can be contacted at HDC Wickersheimer Engineering Services. (3/2010)
- *These reviewers have not returned comment 6/95
- FOUNDATION CRACK EVALUATION discusses detail the process of evaluating foundation cracks and signs of foundation damage by examining the crack size, shape, pattern, and location.
FOUNDATION BULGE or LEAN MEASUREMENTS explains a simple method for determining how much bulge or lean is present in a foundation or wall,
FOUNDATION MOVEMENT ACTIVE vs. STATIC helps determine if the foundation movement is ongoing,
FOUNDATION DAMAGE SEVERITY discusses how we decide the severity of foundation damage and the urgency of further action.
FOUNDATION FAILURES by TYPE & MATERIAL describes the types of foundation damage, cracks, leaks, or other defects associated with each type of foundation material (concrete, brick, stone, concrete block, etc.).
- Masonry structures: The Masonry House, Home Inspection of a Masonry Building & Systems, Stephen Showalter (director, actor), DVD, Quoting:
Movie Guide Experienced home inspectors and new home inspectors alike are sure to learn invaluable tips in this release designed to take viewers step-by-step through the home inspection process. In addition to being the former president of the National Association of Home Inspectors (NAHI), a longstanding member of the NAHI, the American Society of Home Inspectors (ASHI), and the Environmental Standard Organization (IESO), host Stephen Showalter has performed over 8000 building inspections - including environmental assessments. Now, the founder of a national home inspection school and inspection training curriculum shares his extensive experience in the inspection industry with everyday viewers looking to learn more about the process of evaluating homes. Topics covered in this release include: evaluation of masonry walls; detection of spalling from rebar failure; inspection of air conditioning systems; grounds and landscaping; electric systems and panel; plumbing supply and distribution; plumbing fixtures; electric furnaces; appliances; evaluation of electric water heaters; and safety techniques. Jason Buchanan --Jason Buchanan, All Movie Review
- Masonry Design for Engineers and Architects, M. Hatzinikolas, Y. Korany, Canadian Masonry (2005), ISBN-10: 0978006100, ISBN-13: 978-0978006105
- Masonry Structures: Behavior and Design, Robert G. Drysdale, Ahmid A. Hamid, Lawrie R. Baker, The Masonry Society; 2nd edition (1999), ISBN-10: 1929081014, ISBN-13: 978-1929081011
- Masonry, Engineered: Using the Canadian Code, J. I. Gainville, Cantext publications (1983), ASIN: B0007C37PG
- Masonry, Non-reinforced masonry design tables, Hans J. Schultz, National Concrete Producers Association and the Canadian Masonry Contractors Association (1976), ASIN: B0007C2LQM
- Moisture Control in Buildings, U.S. Department of Energy
- Moisture Control in Walls, U.S. Department of Energy
- "Vapor Barriers or Vapor Diffusion Retarders", U.S. DOE: how vapor barriers work, types of vapor diffusion barriers, installing vapor barrier
- Ventilation for energy efficient buildings, Purpose, Strategies, etc.,
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
 The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
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- Building Failures, Diagnosis & Avoidance, 2d Ed., W.H. Ransom, E.& F. Spon, New York, 1987 ISBN 0-419-14270-3
- Building Pathology, Deterioration, Diagnostics, and Intervention, Samuel Y. Harris, P.E., AIA, Esq., ISBN 0-471-33172-4, John Wiley & Sons, 2001 [General building science-DF] ISBN-10: 0471331724
ISBN-13: 978-0471331728
- Building Pathology: Principles and Practice, David Watt, Wiley-Blackwell; 2 edition (March 7, 2008) ISBN-10: 1405161035 ISBN-13: 978-1405161039
- Construction Drawings and Details, Rosemary Kilmer
- Diagnosing & Repairing House Structure Problems, Edgar O. Seaquist, McGraw Hill, 1980 ISBN 0-07-056013-7 (obsolete, incomplete, missing most diagnosis steps, but very good reading; out of print but used copies are available at Amazon.com, and reprints are available from some inspection tool suppliers). Ed Seaquist was among the first speakers invited to a series of educational conferences organized by D Friedman for ASHI, the American Society of Home Inspectors, where the topic of inspecting the in-service condition of building structures was first addressed.
- Domestic Building Surveys, Andrew R. Williams, Kindle book, Amazon.com
- Defects and Deterioration in Buildings: A Practical Guide to the Science and Technology of Material Failure, Barry Richardson, Spon Press; 2d Ed (2001), ISBN-10: 041925210X, ISBN-13: 978-0419252108. Quoting:
A professional reference designed to assist surveyors, engineers, architects and contractors in diagnosing existing problems and avoiding them in new buildings. Fully revised and updated, this edition, in new clearer format, covers developments in building defects, and problems such as sick building syndrome. Well liked for its mixture of theory and practice the new edition will complement Hinks and Cook's student textbook on defects at the practitioner level.
- Guide to Domestic Building Surveys, Jack Bower, Butterworth Architecture, London, 1988, ISBN 0-408-50000 X
- "Avoiding Foundation Failures," Robert Marshall, Journal of Light Construction, July, 1996 (Highly recommend this article-DF)
- "A Foundation for Unstable Soils," Harris Hyman, P.E., Journal of Light Construction, May 1995
- "Backfilling Basics," Buck Bartley, Journal of Light Construction, October 1994
- "Inspecting Block Foundations," Donald V. Cohen, P.E., ASHI Reporter, December 1998. This article in turn cites the Fine Homebuilding article noted below.
- "When Block Foundations go Bad," Fine Homebuilding, June/July 1998
- Historic Preservation Technology: A Primer, Robert A. Young, Wiley (March 21, 2008)
ISBN-10: 0471788368 ISBN-13: 978-0471788362
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