Frequently Asked Questions - Architects

BIA publishes a series entitled Technical Notes which contains our most current information available on brick. This series covers a broad range of topics including design, specifications, properties, and construction. TheTechnical Notes present the most up-to-date in formation available on brick from BIA staff engineers. Most of the topics and answers given in this Frequently Asked Questions feature are derived from the Technical Notes.

Homes have been built for hundreds of years with the knowledge that brickwork is not impervious to water. Water can migrate into brickwork. Brickwork handles this moisture by either having a cavity or separation between itself and the wall behind it or by being so thick that it acts as a barrier to the water.

For a drainage wall, water travels down the backs ide of the brick in the air space and is then channeled out with flashing (metal or plastic sheet) sloped toward the face of the wall and weep holes (small openings or tubes) spaced every few brick at the mortar joints. These flashing and weep holes should be located above all doors and windows, below all window sills, and above the ground at the base of the wall. In a barrier wall, the mass of the brickwork keeps the interior of the wall dry by allowing water to evaporate before proceeding all the way through the wall. Only under prolonged exposure to sustained moisture or rain will a barrier wall exhibit moisture on the interior. When this occurs, the moisture then drains down the back of the wall into flashing at the base which channels it out through weep holes.

The overwhelming majority of brickwork is properly detailed and constructed, experiencing no moisture problems. In the few instances where moisture is a problem, it can be attributed to poor construction or detailing in the brickwork. It is important to maintain a clean space behind the brick in drainage walls. Full contact between mortar and bricks and proper installation of flashing and weep holes are also important to ensure the highest water penetration resistance. Applying and maintaining a proper sealant around window and door openings also plays a vital role in keeping moisture out.

For additional information on water penetration resistance of brick, see Technical Notes 7, 7A and 7B.

For additional information on cleaning, see Technical Notes 20.

ASTM C 67 contains a freezing and thawing test which is presently the industry accepted standard. This test should be conducted prior to delivery of brick to the job site. Bricks pass the test if, after 50 freeze/thaw cycles, they do not exhibit significant weight loss, breaking, or cracking. The test is designed to be performed on brick that have not yet b een built into a wall.

There are many factors that contribute to brickwork's ability to withstand cyclical freeze/thaw including workmanship; the mortar type, its air content and consistency when laid; and the degree of saturation in a wall. These factors cannot be tested for in ASTM C 67 since they involve other elements outside the brick itself. 

Consequently, it is not a forgone conclusion that a brick that passes the test will not experience adverse effects when incorporated into brickwork. Attention to proper design, detailing and workmanship can assure a durable wall assembly.

ASTM C 67 contains a freezing and thawing test which is presently the industry accepted standard. This test should be conducted prior to delivery of brick to the job site. Bricks pass the test if, after 50 freeze/thaw cycles, they do not exhibit significant weight loss, breaking, or cracking. The test is designed to be performed on brick that have not yet b een built into a wall.

There are many factors that contribute to brickwork's ability to withstand cyclical freeze/thaw including workmanship; the mortar type, its air content and consistency when laid; and the degree of saturation in a wall. These factors cannot be tested for in ASTM C 67 since they involve other elements outside the brick itself. 

Consequently, it is not a forgone conclusion that a brick that passes the test will not experience adverse effects when incorporated into brickwork. Attention to proper design, detailing and workmanship can assure a durable wall assembly.

A flashing material must be impervious to water, tough enough to withstand construction abuse and yet flexible enough to conform to the desired shape, and not deteriorate while in service. It should also not react with mortar or corrode and should be compatible with joint sealants.

Traditionally, copper sheet has been used as flashing in masonry walls. Stainless and galvanized steel sheet have also been used as flashing. More recently, plastics and combination flashings have found their way into masonry walls. While there are pros and cons to each type of flashing and a range of cost associated with each, they will all perform satisfactorily as long as they meet the basic criteria for a flashing material.

For additional information on flashing, see Technical Notes 7A.

There are two primary reasons steel stud parapets are advised against. The increased possibility of water penetration and resulting corrosion is one issue. A parapet is externally exposed on three sides making it one of the most vulnerable areas of a building. Furthermore, it is insulated differently than the wall below and can potentially be subjected to more thermal-related issues than other parts of a wall. Water penetration is also more likely due to rain or condensation. This water penetration could lead to corrosion and other future problems.

The second issue deals with the differential movement of the brick and steel stud. The stud can expand at a much higher rate than the brick. This could effect the coping used on the top of the wall and surrounding mortar joints. 

Obviously, these issues can be dealt with in design and construction, but BIA has seen some problems in the past with this type of assembly.

Brick costs more than some other commonly used siding materials because brick is a premium product, but it's not nearly as expensive as you might think. In many parts of the country, a new brick home will cost you only a small percentage more than a comparable vinyl-sided home. Other products, such as artificial stucco, cost about the same as brick, but are far less durable and require much greater maintenance and upkeep.

Brick is a building material that has exceptional "thermal mass " properties. Thermal mass is the ability of a heavy, dense material to store heat and then slowly release it. For you, this means that during the summer months your brick home stays cool during the hottest part of the day. During the winter, brick walls store your home's heat and radiate it back to you. Vin yl, aluminum, wood or EIFS (artificial stucco) are all thin, light building materials that don't have good thermal mass properties. The superior thermal mass qualities of brick have been known for centuries. Most notably, the Pueblo Indians in the Southwest used adobe masonry to moderate weather extremes and keep their homes comfortable.

Single-face fireplace dimensions including the firebox depth, width and height along with the proportionate flue size are given in Technical Notes 19. This Technical Notes also addresses all the necessary features in a brick fireplace and their relationship to one an other. Additional details are provided in Technical Notes 19A while proper chimney construction is outlined in Technical Notes 19B.

A brick's color can be attributed to its clay composition, any added compounds, its firing temperature and any surface treatments. Because brick is composed of naturally occurring materials, all brick will not necessarily be exactly the same. For this reason, some brick may be of a slightly different color than others in a given batch. Usually, this adds character to a wall, but occasionally it is desired to blend these brick with other brick in the wall. This can be done by individually staining the brick in question.

Staining is a common practice and is usually done by a professional with expertise in its application. The stain itself is a proprietary product made specifically for brick. A local brick supplier in your Yellow Pages should be consulted for a product and professional applicator. Since the surrounding mortar joints must be masked, it is a time consuming process and is usually only done when a limited number of brick are involved. If staining is done properly, it should have no detrimental effect on the bricks and should provide a long lasting finish.

Since the primary ingredient in brick is clay which is fired to around 20008 F, it is a non-combustible material. As such, it is an excellent cladding choice to resist or confine fires. A brick wall's fire resistance rating can be calculated. This is done by extrapolating from known fire resistance periods for a given thickness of wall. Refer to Technical Notes 16B for further information on how to calculate fire resistance ratings for specific brick walls. Currently, there are four Underwriters Laboratories tests which have assigned fire resistant ratings to specific wall assemblies. They include U302, U418, U425 and U902. U302 yields a 2 hour rating and involves a brick veneer drainage wall with wood studs and gypsum sheathing and wallboard. U418 and U425 vary in rating between æ to 2 hours and are brick veneer drainage walls with steel studs and gypsum sheathing and wallboard. U902 consists of a drainage wall with brick veneer and concrete masonry units and has a 4 hour rating.

For further information on fire resistance of brick, see Technical Notes 16 and 16B.

Generally, water repellents are only an interim solution to any water penetrating a brick wall since they loose their ability to repel water after 1 to 10 years. However, in cases where all other options have been exhausted, it may be considered as long as one is aware of the inherent nature of water repellents.

There are basically two t ypes of water repellents: films and penetrants. Films such as acrylics, stearates, mineral gum waxes, urethanes and silicone resins form a thin membrane over the brick. Penetrants such as silanes, siloxanes and blends actually penetrate the brick surface. Films are good at repelling water but poor at permitting water vapor transmission which allow the wall to breathe. Penetrants, on the other hand, are good at both. They will usually have a matte finish while films may produce a higher sheen. Penetrants are more acceptable since they allow any water present in the brick to exit the wall. However, penetrants will not provide graffiti-resistance to a wall while some films will. 

Application of a water repellent does not negate proper brick construction and detailing procedures. Any deficiencies in a brick wall such as inadequate flashing, weep holes, mortar joints or broken brick should be corrected prior to the application of a water repellent. The wall should also be cleaned and allowed to th oroughly dry before administering a water repellent.

For additional information on water repellents, see Technical Notes 6A.

ASTM C 67 has a method to test for efflorescence, but it is meant to be conducted before the brick are shipped to the job. While it will not result in a quantitative amount of efflorescence present, it will indicate if the brick effloresces or not. Unfortunately, this test is not appropriate for brick that have already been built into a wall.

Chemical tests on existing efflorescence could be done to find the type of salt present. A masonry consultant should be contacted to make this determination.

For additional information on efflorescence, see Technical Notes 23 and 23A.

Cleaning is much easier if care is taken during application to avoid smearing mortar on the faces of the thin brick. Special grout release chemicals may be applied to the brick before the joints are filled to make cleaning easier. 

Water may be used to remove much of the adhesive and mortar before they have set. Remove cementitious mortars according to recommended cleaning procedures for thin brick. Procedures vary due to color and texture' Remove other mortars according to manufacturer's instructions. Remove dried adhesive according to the adhesive manufacturer's instructions. Do not saturate the surface or smear. Never use muriatic acid, wire brushes or other abrasive methods to clean thin brick. 

As always, the wall should be thoroughly saturated with water before and after any cleaning application. Also, a small inconspicuous area of wall should be tested to confirm that any solutions used will not harm the brick. Freshly applied paint can be removed with a solution of trisodium phosphate mixed with water at a rate of 2 lb. per gallon of water. Apply the solution to the brick; allow it to soften paint; and remove with scraper and stiff bristle brush. Proprietary chemical compounds are also available through local distributors to remove fresh paint. Existing paint which has been in place for some time is more difficult to remove and may require using abrasive techniques with non-steel scrapers or sandblasting by a professional. Certain brick should not be sandblasted. Proprietary chemical compounds from local distributors in the form of a gel solvent may be necessary to soften existing paint. Numerous applications may be necessary depending on the number of paint layers. For additional information on removing paint from brickwork, see Technical Notes 20.

Most stains and discoloration can be removed from brickwork if the proper cleaning technique is employed. There are essentially two categories of stains; those which are externally applied to the wall and those which originate from within the wall. Those which come from within a wall may need additional investigation to prevent the stain from returning. As always, it is important to thoroughly saturate a brick wall before application of any cleaning solution. As a general rule, acidic cleaning solutions should only be applied to red brick with no surface finish such as sand. Also, an inconspicuous area of the wall should be tested with any cleaning solution for compatibility prior to application on the entire wall. Any cleaning solutions should be thoroughly rinsed from the wall. Most stains can be dealt with by thoroughly washing the wall with a common household or kitchen cleanser dissolved in water and applied to the wall with a stiff bristle brush. If this is ineffective, a poultice which dissolves the stain and pulls it into an inert material may be necessary. The inert material can be talc, whiting or fuller's earth while the solvent will vary based on the type of stain. Proprietary cleaning agents can also be employed to remove specific stains. Sandblasting and pressure washing brickwork can also be options for certain brick when especially stubborn mortar or externally applied stains are involved. Bricks with coatings such as sand or slurry finishes should not be cleaned in this manner. Sandblasting and pressure washing should usually only be undertaken by a competent professional with experience. If improperly executed, either of these methods can permanently damage the brick. For more information on stain removal, see Technical Notes 20.

To answer this question, you need to understand the consequences of leaving or removing plant growth. This growth on brick can potentially damage it by forcing root tendrils into the mortar joints. Moisture can then find its way into the wall and freeze-thaw action or other moisture related events can occur resulting in damage. However, ivy also sheds rainwater and reduces the surface temperature of the wall. Properly constructed walls with good workmanship and well-tooled joints can also resist tendril intrusion better than poorly constructed walls. 

When existing plant growth is removed from a brick wall, it may also remove part of the mortar from the joint. This could result in the wall having to be repointed by removing any broken mortar and repacking with new. Further, complete removal of the tendrils is difficult. Failure to do so may result in stains on the wall. 

Therefore, it is an evaluation which is best made by the owners taking these as well as the aesthetic and economic considerations into account. While plant growth can shorten the life of brickwork, a well-constructed wall should still last for many decades. 

Additional information on plant growth on brickwork is available by ordering Engineering and Research Digest #621 from the Brick Bookstore

Weep systems in use include wicks, oiled rods, weep tubes, open head joints, and vents. BIA does not advocate one type of weep system over another. Wicks should be spaced at 16" o.c. with the remainder of the weep systems spaced at 12" o.c. Rope wicks can be made from cotton sash cord. Drainage materials used at the bottom of the cavity are most effective for open type of weep holes like open head joints, weep tubes, etc., however it could be used with rope wicks. It is important to maintain a clean, open cavity for weep holes to function properly. If mortar droppings are anticipated, then it is best to detail a drainage material that will catch any mortar like pea gravel or mesh.

For additional information on weep holes, see Technical Notes 7.