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Masonry veneer wall vent details & specifications

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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.



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Brick Veneer Wall Through-Ventilation - Airflow Removes Moisture?

Cracks in brick veneer wall (C) Daniel Friedman

[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.

Brick veneer cavity wall showing air space behind the veneer, adapted from Arumala 2007 (C) InspectApedia.com

[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:

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) 

Reader Question: Brick veneer vents extending in a straight line from foundation to roof?

(Apr 18, 2014) Rodney Thompson said: Have you ever heard of a weep hole extending in a straight verticle [sic] line from the foundation to the roof?

Reply: not quite, but ...

Rodney,

Not exactly, Rodney. But in some veneer and cavity wall construction, indeed vents are placed at intervals in upper sections of the wall. These vents are in addition to, not in place of veneer wall bottom water drain and vent openings.

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". Just how much air moves in that path is debatable, as we discuss at BRICK VENEER WEEPS BLOCKED or MISSING.

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

Or see BRICK WALL DRAINAGE WEEP HOLES - home

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