Installed Correctly, Brick Veneer Lasts a Long Time
Brick-veneered houses need good moisture details
Most new brick houses are actually wood-framed buildings with a thin masonry facing. Brick is a low-maintenance, durable siding choice, as long as it's installed with details designed to handle moisture intrusion. If installation errors are made, however, repairs are usually very expensive.
The expense and the weight are two main drawbacks to brick-faced wall assemblies. The energy used to transport such a heavy product drops it a few notches down on the green scale. Setting brick is labor-intensive, and skilled masons may not be as easy to find as carpenters who can install other types of siding.
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AIR SPACES AND FLASHING
Choosing flashing for brick
Although the flashing used on commercial installations of brick veneer is often made of stainless steel or copper, residential masons usually install EPDM or self-adhering rubberized asphalt flashing. Polyethylene, housewrap, and asphalt felt are not acceptable flashing materials. Aluminum corrodes when embedded in mortar, so it should never be used for flashing brick.
Timeless and time-tested
Brick has been around for thousands of years and is still a popular building material in many parts of the world. Although the embodied energyEnergy that goes into making a product; includes energy required for growth, extraction, and transportation of the raw material as well as manufacture, packaging, and transportation of the finished product. Embodied energy is often used to measure ecological cost. of a brick-clad wall can be more than twice that of one with wood siding, a well-detailed brick wall will go for decades with minimal maintenance.
One undervalued principle of green building is that an aesthetically pleasing building is more sustainable; people tend to take care of beautiful things. Brick structures can have a character and mass that signify permanence more than other materials.
Although the graceful proportions of a well-designed brick home can provide timeless appeal, it's also important to pay attention to water-management details that ensure the longevity of a brick facade.
Flashing at windows
At a window head, install through-wall flashing that includes a vertical leg covered by the water-resistive barrierSometimes also called the weather-resistive barrier, this layer of any wall assembly is the material interior to the wall cladding that forms a secondary drainage plane for liquid water that makes it past the cladding. This layer can be building paper, housewrap, or even a fluid-applied material.. The flashing covers the steel lintel and projects beyond the vertical plane of the brick veneer. Weep holes are required at window heads.
At window sills, the through-wall flashing begins at the the rough sill, has a vertical leg, and then projects to the exterior beyond the plane of the brick veneer.
Ventilation and flashings are the law
The proper installation of masonry veneer is covered in IRCInternational Residential Code. The one- and two-family dwelling model building code copyrighted by the International Code Council. The IRC is meant to be a stand-alone code compatible with the three national building codes—the Building Officials and Code Administrators (BOCA) National code, the Southern Building Code Congress International (SBCCI) code and the International Conference of Building Officials (ICBO) code. Section 703.7, with common installation details shown in accompanying Figure 703.7. All masonry veneer must be over an approved water-resistive barrierSometimes also called the weather-resistive barrier, this layer of any wall assembly is the material interior to the wall cladding that forms a secondary drainage plane for liquid water that makes it past the cladding. This layer can be building paper, housewrap, or even a fluid-applied material. and anchored to the underlying substrate with corrosion-resistant metal ties spaced a maximum of 24 inches both vertically and horizontally (703.7.4). Additional ties are required around window and door openings (703.7.4.1.1). The veneer should be separated from the sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. with a 1-inch to 4 1/2-inch air space (703.7.4.2), or alternatively, the space can be filled with mortar or grout (703.7.4.3).
Flashing directs infiltrated water
Corrosion-resistant flashing must be installed between any means of support and the first course of brick or stone above it (703.7.5) and include 3/16-inch weep holes every 33 inches immediately above the flashing (703.7.6). Flashing must also be installed over windows and doors, over projecting wood trim, above roof intersections, and anywhere a wood framing interrupts or attaches to the veneer, including porches, decks, and exterior stairs (section 703.8).
Depending on the area’s seismic activity and the percentage of exterior walls covered by structural sheathing, the height and weight of the veneer may be limited (Table 703.7).
Good water-management details ensure durability
Facing a wood-framed building with brick is a good way to get the look of traditional masonry at a lower cost than traditional construction methods. Brick is fire- and insect-resistant, needs very little maintenance, and is one of the most durable wall claddings available — as long as flashing and moisture details are well thought out and executed.
Brick veneer is an attractive option from an energy standpoint because its lighter weight translates into lower transportation costs and simpler foundations. It is easier and faster to install than full-thickness brick. If the installation is carefully detailed to handle water intrusion and inward solar vapor drive, thinner brick should prove durable with a minimum of maintenance.
Because brick is so durable, salvaged brick often can be reused. But check it carefully and make sure it's sound. Not all salvaged bricks should be used outside where freezing temperatures can be expected.
MORE ABOUT BRICK
Brick-veneered walls must be painstakingly detailed to prevent water intrusion, because fixing problems, especially faulty flashings, is extremely expensive once a house is built.
A necessary air space. Brick veneer is installed with an air space behind it to drain any water that penetrates the invisible cracks in bricks and mortar. The space also provides a capillaryForces that lift water or pull it through porous materials, such as concrete. The tendency of a material to wick water due to the surface tension of the water molecules. break to interrupt the flow of water to the interior of the wall. It is the mason's responsibility to prevent accumulated mortar droppings from clogging the air space; verifying this component of the work is one of the most problematic aspects of brick-veneer construction.
Weep holes. Weep holes at the base of a brick-veneered wall allow water to drain out and ventilating air to enter the wall. The easiest way to make weep holes is to leave out the mortar from some of the head joints between bricks. Weep holes have to be above grade, and homeowners should be warned against burying them with landscaping mulch.
Base flashing is code mandated for brick veneer jobs. The flashing must be installed to direct water running down the water-resistive barrierSometimes also called the weather-resistive barrier, this layer of any wall assembly is the material interior to the wall cladding that forms a secondary drainage plane for liquid water that makes it past the cladding. This layer can be building paper, housewrap, or even a fluid-applied material. (WRB) through the weep holes to the exterior. Flashing and weep holes are also necessary above projections like bay-window roofs.
Inward solar vapor drive. Brick is a reservoir claddingMaterials used on the roof and walls to enclose a house, providing protection against weather. , meaning that it absorbs and holds water after a rainstorm. Once the sun comes out, the wet bricks try to dry in both directions, which can push moisture into the building, a phenomenon known as inward solar vapor drive.
A well-detailed brick veneer installation requires vapor-impermeable housewrap or sheathing to slow inward solar vapor drive. In most cases, extruded polystyrene or polyisocyanurate foam are the best sheathings to use under brick veneer. Vapor-permeable sheathings like Celotex should never be used behind brick veneer.
For more information on inward solar vapor drive, see When Sunshine Drives Moisture Into Walls.
A DIFFERENT MIX FOR DIFFERENT BRICKS
Some types of brick call for wetter or drier mortar
All bricks absorb water through microscopic pores, and they do so at different rates. The rate at which bricks absorb water from mortar is called the initial rate of absorption (IRA), and knowing the bricks' IRA can reduce the amount of cracking and separation that occurs later.
If the brick absorbs water too quickly from the fresh mortar, little water will be left to adequately hydrate the portland cement in the mortar, and subsequent cracking within the mortar may occur. If the brick absorbs too little water, however, a weak bond forms, causing the mortar to separate from the brick.
Mortar recipes can be adjusted, if necessary, to accommodate the brick's IRA, which can be obtained directly from the brick manufacturer. A brick that has an IRA above 25 grams per minute per 30 square inches is considered very absorptive, and an IRA below 5 grams per minute per 30 square inches is considered low. For a very absorptive brick, make one of these adjustments:
Add a little more water to the mortar, and wet the bricks before installation (except in cold weather).
Add more hydrated lime within the limits of ASTMAmerican Society for Testing and Materials. Not-for-profit international standards organization that provides a forum for the development and publication of voluntary technical standards for materials, products, systems, and services. Originally the American Society for Testing and Materials. C270.
Use a workability-enhancing admixture that conforms to ASTM C1384.
For a low IRA, the brick manufacturer's recommendations may include one or all of the following adjustments:
Reduce the amount of water used in the mortar.
Keep the brick dry before installation. For more details on bricks, mortars, and techniques, contact the Brick Industry Association (703-620-0010; www.bia.org) and the American Society for Testing and Materials (610-832-9585; www.astm.org).
—from Fine Homebuilding
- Don Mannes/Fine Homebuilding #142
- Roe A. Osborn/Fine Homebuilding #142
- Dan Morrison/Fine Homebuilding #192
Mar 31, 2010 1:32 PM ET
Mar 31, 2010 12:07 PM ET