Vapor-Retarding Membranes for Back-Up Walls Modesto CA

Applying a rubberized asphalt membrane over the surface of the concrete masonry would make a more effective vapor-retarding membrane than would an application of an asphaltic paint in Modesto.

Design Masonry Group
(209) 466-6646
4500 E Fremont St
Stockton, CA
 
O'Donnell Plastering
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2318 Lafayette St
Santa Clara, CA
 
Ovels Masonry
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8576 Ferncrest Way
Elk Grove, CA
 
Modular Masonry Inc.
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Roy'S Concrete Construction & Masonry Inc
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22223 Mariposa Ave
Torrance, CA
 
Solano Chimney Sweep
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128 Charles Ct
Vallejo, CA
 
Hawksley Masonry
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2624 Verne Roberts Cir Ste 106
Antioch, CA
 
Free Lance Masonry
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15432 Hanover Ln
Huntington Beach, CA
 
Astro Enterprises
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420 Humboldt Rd
San Francisco, CA
 
Ed'S Landscaping
(626) 793-5296
3320 Mills Ave
Glendale, CA
 

Vapor-Retarding Membranes for Back-Up Walls

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Source: MASONRY CONSTRUCTION MAGAZINE
Publication date: November 1, 1999

I have heard people recommending asphalt coatings for the exterior face of the concrete masonry back-up wall in cavity wall construction to act as a vapor-retarding membrane. This is particularly true with an exterior wythe of glazed brick. If the intent is to create a vapor-retarding membrane on the surface of the block, wouldn't it be better to use an impervious sheet membrane, such as rubberized asphalt? The surface of the concrete masonry is typically very rough, and an asphalt coating would typically contain pinholes.

Applying a rubberized asphalt membrane over the surface of the concrete masonry would make a more effective vapor-retarding membrane than would an application of an asphaltic paint. However, before applying any coating, you must ask yourself whether this is the proper place for a vapor-retarding membrane. A vapor-retarding membrane should be on the warm side of the insulation. Therefore, over a large portion of the United States, the heating season dictates that the vapor barrier be on the interior side of the insulation. For insulated cavity walls, this would be the exterior surface of the concrete masonry backup wythe. However, when insulation is not placed in the cavity, it would typically be either within the cells of the masonry backup or on the interior surface of the concrete masonry.

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