Vent openings or holes in brick & other masonry veneer walls:

This article discusses ventilation in the cavity behind brick or other masonry walls in veneer wall construction and the use of intermediate and wall top air vents or intermediate drains in some veneer wall designs.

This article series 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.

Brick Veneer Wall Through-Ventilation - Airflow Removes Moisture?

[Click to enlarge any image]

Above: wall vents placed mid-height in a tall brick veneer wall on a Vassar College building, Poughkeepsie, New York USA.

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.

[Click to enlarge any image]

Shown above the blue indicates the air space behind a brick veneer wall with weep openings at bottom (circled in green ) and sealant at the wall top (circled in dark blue). Some veneer walls include vents at intermediate and upper levels of the cavity wall as well as the basic drain/vent openings at the wall bottom. This illustration is adapted from Arumala (2007).

Typically and as recommended by the BIA, we see 2-inch (51mm) air space between the inner face of the brick or stone veneer and the surface of the building sheathing.

Special Corrosion Concern with Air Leakage in Veneer Walls on Metal Stud-Framed Buildings

Watch out: corrosion problems in metal stud framed walls behind brick veneer walls has been a problem in some buildings and appears related to even low rates of air leakage and flow in the wall cavity. (Arumala 2007 in turn citing others).

It has been reported that the brick veneer steel stud wall system is vulnerable to moisture damage [Cowie (1990)]. In environmental studies done on the wall system, it was found that corrosion of the galvanized steel studs was detected a few days after the start of the tests and at a low rate of air leakage flow [Drysdale et al. (1989)].

Gumpertz and Bell (1985) evaluated the wall system and reported the investigation of problems with brick veneer steel stud walls on twelve buildings. All the reported corrosion problems on the wall system were traced to the effect of water and water vapor penetration of the wall system.

In fact excessive moisture penetration into and accumulation in the cavity and the condensation of moisture in the wall have the potential of causing corrosion in:

• the brick-tie connections to the studs,
• the studs themselves,
• the threads of the fastener screws

BIA Technical Notes 28B give guidelines for design and construction of the system including the selection of materials, ties, studs, vapor barriers and air retarders, proper installation of weep holes and flashings, insulation and placement of expansion joints to minimize this problem.
- (Arumala 2007) 

Research & Standards on Brick Veneer Wall Vents

• Arumala, Joseph O. "Brick Veneer Steel Stud Wall Systems: State-of-the-Art." The Masonry Society Journal (2007): 9-19. Illustrations used in this article series include adaptations from this article and from BIA Technical Notes 28B shown below.
• Brick Industry Association, [BIA], "Brick Veneer / Steel Stud Walls, 28B", [PDF] Brick Industry Association, op.cit. (December 2005), retrieved 2016/06/21, original source: http://gobrick.com/Portals/25/docs/Technical%20Notes/TN28B.pdf Excerpt included in the article above
• Also seeReferences or Citations for this article

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Question: Leaks & mold growth in brick veneer walls that admit water during flooding

(Mar 13, 2012) WEill said:

if water enters the weep holes during a spell of high water, and allows some water into the building. if the sheet rock is not wet, will mold still grow inside the wall? if so how should i dry it out?

(Feb 18, 2013) Levertis Steele said:

Water rises above the weep holes when it rains in my backyard for several hours. Water seeps in from somewhere and covers most of the room it enters. After the rain stops and the water level outside recedes, the water drains from the room in the same direction from where it came. I thought that it was coming through the weep holes. What is wrong?

Reply: lower the water or raise the house

Will:

Even with a lot of experience with mold detection and remediation in buildings I can't say for certain that mold will or won't grow at a specific location on a house I've never seen. But certanly drywall is very mold friendly. If drywall is wet or even if it's not, if there is water inside a wall cavity that sends moisture higher in the wall cavity to where drywall is located, you can expect problematic mold growth to show up.

You can explore the suspect area for visible mold by making a test cut into the most-suspect location. Check the cavity side of the drywall for visible mold and also check nearby wood framing and insulation.

Levertis:

Periodic area flooding that is submerging a building wall to heights above the top of the foundation wall suggests some more serious steps are needed to control floodwaters, or if that's not going to be reasonable or reliable, to live with water entering the property, structural design changes are needed.

In an area of very limited water and rot problems on a flat site in New York, I addressed a water entry and related rot/insect damage problem by chopping off the bottom two feet of a wood frame wall and building up the wall base with a couple of courses of solid concrete block.

Question: ok to cover up weep openings ?

(Sept 11, 2012) Anonymous said:

I have weep holes located on the 2nd floor of my house. above and below a window and also a few towards the base of the 2nd floor. Can these be covered up?

Reply: no, probably not

Closing off weep openings in a masonry wall, presuming that they were properly located, installed, and flashed in the first place, risks trapping wind-blown rain or other water inside the wall cavity, inviting structural damage, rot, or mold contamination.

Question: Masonry wall weep holes vs Wind-blown rain water entry

(Sept 22, 2012) dena said:

we have water after a blowing rain coming over the brick ledge which sits on the basement foundation .the water did not drain out due to the builder installing the flashing wrong it is on the outside of the tyvak.the moisture caused the vapor barrier to condense and now we have a mold problem. can we remove several couses of brick to repair the flashing?

a builder wants to remove all the brick around the house which is very expensive and money we don't have as we are senior citizens and in bad health.

a masonary man says he can remove several courses by leaving some of the bricks every 5 feet.can this be done?

Reply:

I think your mason may have more experience with brick veneer than the builder, and his suggestion is worth a try. But be careful. 5 feet as the drainage opening interval may be too big a gap.

An unknown is the number and spacing of ties to the wall structure. If the wall is not supported enough and thus cracks you'll end up removing it all. Try working on just one segment at a time and perhaps leave more bricks loose but in place, removing the temporary support ones just briefly during repair and re- flashing. Send me some photos and perhaps we can comment further.

Question: flashing snafus mean leaks blamed on weep holes

4-17-2014 Ted said:

I have weep holes above my windows and door. The rear of the house is exposed to blowing wind and rain. I have leaks in three windows, one easily seen dripping from the top window frame the others I suspect are running down around the edge of the window and coming out below the window from the lower trim, running down the inside walls.

I had the windows caulked and as an add on the contractor, as a favor, added metal wrap to the lentil and caulked around that too. First really heavy wind and rain storm came and now the leaks seem worse.

I suspect the flashing must have been run out through the lentil and that wrap and caulk job are the reason it's worse. Am I correct in that thought? Should I take the wrap off of the lentils? How should I check for proper flashing as I had leaks before the wrap and caulk job?

Reply:

Ted, I agree that it sounds as if the flashing above windows and doors was omitted or not properly installed or punched or damaged during construction. I can't see how to fix this easily without some exploring into the wall cavity to see what's going on. Check out Carson Dunlop Associates' page top sketch (click to enlarge any image) to see what the flashing position should be.

Keep in mind that even if the flashing is properly installed, if a lot of water is leaking into the wall from higher-up, the water might be running down the wall sheathing and behind the flashing and out from underneath it. That diagnosis is what's needed before we try to fix anything.

Watch out: Certainly we don't want to just close off weep openings or caulk in the wrong place or we risk either water accumulation in the wall or severe rust and lintel damage.

Question: do weep hole vents extend from foundation to roof line?

4/18/2014 Rodney Thompson said:

Have you ever heard of a weep hole extending in a straight verticle line from the foundation to the roof?

Reply:

Rodney,

A weep opening in a brick veneer wall is placed at intervals and at one or more location heights always including the wall bottom and possibly at higher points in the wall depending on how the wall is constructed.

The open space behind a brick veneer wall is typically intermittently partially obstructed by extrusions of mortar in the veneer, depending on how the wall was built, but hopefully nowhere is the air space totally obstructed across the whole width of the wall - so moisture can find its way to a weep opening for exit.

SO yes the air space behind a veneer wall extends, though irregularly, from wall base to wall top. But no, not explicitly in a "straight line".

The "wall top" may not extend to the roof line - that depends on how the building is designed and how high the veneer wall extends.

Question: when to close off weep or drain openings in walls

(June 4, 2014) Virginia P. said:

I am converting my front porch into a room. The contractors says we can leave the existing brick walls with the weeping holes in place. He wants to keep the wall, and built over it. Some people tell me we should have the brick wall removed so moisture will not built up and create mold. The contractors says its not necessary. I don't know what is correct. What should I do?

Reply:

Virginia,

I don't understand how your existing porch is constructed nor where the weep holes are located in it. If you are describing drain openings in a masonry wall that is earth filled, over which a porch slab was poured, leaving them in place is harmless. In any event the intent of drain or weep openings is to allow rain or other water penetration to exit the structure.

Sealing them, in general, risks future trapped water and a moisture problem or in freezing climates, frost damage.

Question: increasing the length of brick wall weep tubes: owner pouring water behind brick to test for leaks

(July 22, 2014) Anonymous said:

Stucco Tec / I am a brick mason we are laying 60000 brick and using weep tube the home owner has been running water behind are brick to see if the weep tub is working 80% of them are working the others are plugged with mortar that has fallen behind the brick which will happen I am now going to make my tubes longer what do you think is a good idea. Thank You Stucco Tec

Reply:

Anon,

I think the owner is not doing a very good thing to pour water in volumes far greater and at a greater rate than the brick veneer wall design would anticipate - a result risks leaks into the wall cavities, floors below, mold, insulation damage.

It is common for some weep hole openings to become clogged with fallen mortar. If it's just a very few and if weep openings are frequent enough along the wall bottom, it's not likely to be a concern. More important is proper flashing at the wall base to be sure that water is directed out to the weep openings.

However if you detect a clogged weep opening before the mortar is hard-set you might be able to just clear the existing opening or cut it bigger and insert one of the retrofit weep opening products in this article.

Longer tubes at weep openings may still become mortar clogged and certainly you don't want the end of the tube to be jammed up against the sheathing of the exterior wall.

What do you think about using some of the other weep opening products shown in the article above. There are products for both original installation and for retrofit.

Question: how to stop interior wall rot *& plaster damage behind brick walls in Salt Lake City

(Sept 1, 2014) Susanora said:
What can I do to stop the wall rot (interior crumbling plaster & also some crumbling of interior ferrocement) behind my 1938 brick - lath walls?

The brick frame house has no weep holes, and the problem is only on the west side along about a 15 feet section, all above grade. I think condensation may be part of the issue - this is in Salt Lake City and driving rains are not frequent.

I have had the house for 24 years and the problem has been continuous - I repaired the interior plaster several times, then gave up & hung cloth over the mess. No mildew or mold, but it is a significant cosmetic problem. Is there any way I can add ventilation from the inside of the house to the airspace behind the brick? It is so arid here (average humidity 15% - 20%) wouldn't it be possible to ventilate the cavity from inside of the wall?

Reply:

Rot, which refers to organic materials like wood, is caused by a combination of water and wood destroying fungi, often basidiomycetes, sometimes more serious Meruliporia.

The right epair is to stop the source of water entry and to determine if structural repairs are needed.

I'd also look for insect damage in the same areas.

If you think condensation is occurring in the wall from indoor humidity I'd look for and fix any sources of indoor moisture and I'd seal penetrations into the wall such as around receptacles.

I would not try venting the wall cavity to the indoors - you may invite IAQ problems.

I would look at some of the brick veneer drain retrofit products we describe in this article.

Question: why need flashing as well as brick wall weep or drain openings?

(Sept 6, 2014) JJ said:
Why is there both weeping holes AND flashing? Can't water get out through flashing alone? I am not understanding the logic: do they both perform the same function? Thanks!

Reply:

No the flashing would be sealed by the mortar course.

The weep holes are the water exit; the flashing is the water director.

Question: ok to omit masonry wall drainage openings in short sections?

7 January 2015 Anonymous said:
I have a long brick exterior wall. Near the end of the wall is a double door and then just a few more lengths of brick prior to the termination of the wall into hardi-plank. Is it needed to install a weep hole in the brick in this short length. There isn't one currently.

I feel there is plenty of weep holes on this wall on the other side of the door to allow for air pressure equalization, but I don't see how moisture could escape between the door and the end of the wall (moisture can't go up and over the door opening to the other side to travel out of those weep holes).

Reply:

Anon

The weep holes' job is less air pressure equalization and more water drainage.

Obviously we don' t need continuous weep openings at the bottom of a masonry wall, the openings are spaced at intervals. However an individual wall section bordered by other structural elements, that is not connected to drained wall sections, should have its own weep openings even if only one is fitted.

Having a weep hole in even that short wall section would reduce the chances of water accumulation therein and thus related building damage.

You can make a further risk or needs assessment if you can inspect the building interior walls below the section you are talking about - e.g. from a basement or crawl space where you'd look for leak signs, and you can also assess risk by noting conditions outside that increase the risk of leaks into that section of wall cavity such as an un-flashed or leaky window, door, or cracks in the brickwork.

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Continue reading at BRICK VENEER WALL LEAKS in FLOOD PRONE AREAS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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  • BRICK VENEER WALL THROUGH-VENTILATION
  • BRICK VENEER WALL LEAKS in FLOOD PRONE AREAS
  • BRICK VENEER WALL REPAIRS in FLOOD PRONE AREAS
  • BRICK WALL DRAIN, FLASHING, VENT SOURCES

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