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Williams-Goodco CMU Vent

Description: The Williams-Goodco CMU vent is an injection molded vent made from flexible polyvinyl chloride in an offset "T" shape. When inserted in vertical mortar joints between two bricks the slotted leg of the vent allows air to pass in and out allows water to weep out and prevents water from penetrating in.
Spacing of CMU Vents: Tests indicate that for interior/exterior air pressure equalization and for ventilation one Williams-Goodco CMU Vent to every 10 square feet of wall surface is acceptable. One per 100 square feet is a minimal number. For drainage of condensation and moisture the vents act as weepholes and should be placed directly on top of the thru-wall flashing. One vent for every 24 inches of horizontal flashing is acceptable to provide weephole drainage.  The vents are hardly noticeable after installation but a regular symmetrical spacing pattern gives the best appearance.
Functions: When rain contacts an exterior surface water can enter openings through any combination of the following actions: momentum of raindrops, capillary action, gravity and air currents. Cracks, joints between wall components, surface pores and inadequately bonded interfaces may provide the openings for water penetration through walls. Much of the water penetration through brick cavity walls is caused not by the driving wind and rain on the exterior face but by the suction created within the air cavity by the lower interior air pressure. This force is controlled by installing brick vents in sufficient frequency and size to allow almost immediate air pressure equalization. Since winds gust, rather than create steady pressure, vents must have enough opening area to allow a continuous exchange of air. Small tubes and wicks have generally proved inadequate because of their limited opening size and because they clog quickly.

Efflorescence: Efflorescence is reduced by minimizing rain wetting within the exterior wall. However, more absorptive CMU products  will hold moisture from exterior rain, or condensation on the back face resulting from air leakage from the building interior, and under certain environmental conditions (particularly in late Fall) this presence of moisture can trigger efflorescence.

Glazes, Paints or Silicones: When these materials are used, cavity walls are necessary to avoid serious problems. In most buildings, moisture laden air will leak from the building interior and unless some free passage is available to the outside, spelling, ice lensing or blistering can occur.

Test Reports: Tests have been conducted to determine the rates of air flow through the Williams-Goodco CMU vent and to indicate acceptable spacing for exterior walls. The test procedures and results are published and available on request.

Material Specifications: The Williams-Goodco CMU vent is manufactured from a polyvinyl chloride compound specifically designed for continuous exposure to weathering. This compound possesses excellent sunlight resistance, good low temperature properties and contains a polymeric plasticizer to ensure permanence. Physical Properties as determined on molded specimens by ASTM procedures:

Packaging: 100 vents per carton.

Color: Light gray.
Special Colors Available.

7-5/8", 11-5/8"
will fabricate special sizes

Short Form Specification: Williams-Goodco CMU vents as supplied by Williams Products, Inc. shall be installed in the vertical mortar joints in the exterior masonry brick wall...

(a) As detailed on the drawings. (b) Directly above all through-wall flashings at (spacing). (c) Throughout the wall in every (i.e. 4th mortar joint) horizontally and every (i.e. 10th course) vertically.

(1) Top-flap - overlaps two adjacent Blocks to stop mortar from falling into the air passage.

(2) Flexible Wings - to adjust to variation in mortar joint widths (5/16" - 3/4").

(3) Louvers - to allow air passages while creating a water barrier.

(4) Water ridges - when water buildup on the exterior wall surface is blown into the air passage these ridges create a barrier which directs the rain down and out of the cavity


Provide adequate opening for immediate air pressure equalization.

Act as weeper.

Provide neat, attractive appearance.

Install easily.

Impede passage of insects, din and rodents.

Block entrance to rain.

Resist clogging and the corrosive effects of masonry mortars.

Please contact us by;  
Phone:  Toll Free 800-521-9594    or      248-643-6400
Fax: 248-643-7117
Email: Wilpro@williamsproducts.net
Rubber, Neoprene, Foam, Gasket, Seal, Construction. To the best of our knowledge this published information is accurate, however, to determine suitability of material/product for a specific application is the user's responsibility.  Williams Products, Inc. shall not be liable for any loss or damage resulting from inappropriate usage.
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Contact Williams Products: Phone: 800-521-9594 or 248-643-6400 or Email: Wilpro@williamsproducts.net  Contact Information