Frequently Asked Questions - Designers

Control Joints are intended to create artificial planes of weakness where stresses in the wall can form their own cracks, breaks, or fissures and at the location of the control joint. 

Atlas™ brick are not normally tested in the same manner as concrete block (CMU). Because of the lower compressive strength of the material, CMU can be tested in a 16" length using testing machines with capacities of 250,000 lb. ratings. Structural brick have unit strengths 4 to 5 times that of concrete block and therefore must be cut into smaller rectangular sections. This is done by cutting the unit in half and removing the 'dog ears' flush with the web to create a rectangular unit. Prisms are also done in the same manner. Testing machines must be rated in excess of 450,000 lb. capacity in order to break the brick within the elastic range of the testing machine. Machines with ratings lower than this may cause premature failure.

The testing machine must also have a spherically seated head that adjusts for slight distortions in the material. A gypsum capping compound is used to cap the units and the prisms to also level out any non-uniformity in the units. 

Unlike concrete products, fired clay brick colors do not fade. Color changes over the years are a result of atmospheric conditions. Soot, dirt, and grime all of which can be cleaned by remedial cleaners. 

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. 

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Visit a brick showroom near you to review your options. You'll have the chance to review hundreds of brick and mortar combinations. To locate a showroom, go to the online Member Directory. Also, be sure to check your local Yellow Pages under "Brick." hundreds of brick and mortar combinations. 

The thin set method omits the moisture barrier, wire mesh, and the scratch coat and only uses the setting mortar or bond coat to the brick. Use the thin-set method on interior surfaces only. 

Brick is the smallest dimension it will be in its long service life when it leaves the kiln. As it is exposed to moisture from a variety of sources including the air, wet mortar, rain and condensation, it will naturally expand since it is a clay product. Temperature will also cause brick to expand and contract. Consequently, it is important to incorporate expansion joints into brickwork to accommodate this movement. Expansion joints should be located where stresses or cracks are likely to develop in brickwork. Prime candidates for expansion joints include long expanses of walls, corners, offsets, setbacks, and parapets. Expansion joints should also be located below shelf angles to account for vertical expansion of brick. When accent bands of other materials such as precast or concrete masonry units are included in a wall, it may be prudent to include a bond break or slip joint between the two dissimilar materials if their coefficients of expansion are significantly different. Bond breaks are created by embedding a smooth sheet such as flashing materials in the mortar bed which allow the materials to move independent of each other. When determining where expansion joints should be placed, it may be necessary to calculate the amount of expansion anticipated. This can be done by knowing the coefficients of expansion of the brickwork and the parameters of its environment. For additional information on expansion joints, see Technical Notes 18 and 18A.

Certain brick colors have integral minerals that may be negatively effected by the cleaning process. Interstate has put together some general recommendations in our Technical Bulletin. Additional information can be retrieved from the BIA Technical Notes 20.

Interstate Brick manufactures a wide variety of shapes which provide architectural details not obtainable by saw cutting standard size brick. The least expensive shapes are extruded. Some shapes are hand formed and are much more expensive. If you do not see a shape on this web site, contact the manufacturer for available options. Link to shapes area of web. 

When structural brick are used, reinforcing in the brick work against the expansion of the brick to post-tension the reinforcing. This reinforcing also is used to transfer the bricks tension into the reinforcing. Spacing of expansion joints can be spaced at greater differences than those for brick veneer. Horizontally reinforced structural brick have performed well with expansion joints at 60 ft. centers. To prevent cracking at corners, continuous reinforcing should be used. Contact the manufacturer for specific recommendations. 

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.

The Quartette is an Atlas™ brick. Frequently a designer wants to scale down the visual appearance of the brick. In this case a slot is placed in the middle of the brick. To achieve a running bond pattern the brick must be laid in quarter or 3/4 bond. To allow the reinforcing to align, the coring must be modified and a starter unit is required at the corners. Quartette flier. 

Thin brick is unlike regular facing brick when it comes to expansion joints. Because of the thickness of the material, the substrate plays a bigger role in the movement of the wall. As most substrates and adhesion materials are concrete products, the primary movement of the substrate is shrinkage. Crack control is placed at the spacings and detail as required for stucco. 

A control joint in stucco is intended to relieve stress and limit or control the cracking in the membrane of the stucco only. Usually installed at a maximum of 144 square feet. It is not necessary and in fact can be detrimental to cut the lath behind the control joints. A control joint will not stop stucco from cracking if the stresses imposed upon the stucco membrane are greater than can be dissipated by the stucco and/or the control joint. 

ASTM C1063 requires that panel areas are no larger than 144 square feet. In addition, the maximum spacing of control joints should be less than 18 ft. The aspect ratio of the panel should also be held to a maximum length to width ratio of 2 1/2 to 1. 

An expansion joint in stucco is a two-piece slip joint that is installed at a similar expansion joint in the structure of building. When installing an expansion joint, the framing, sheathing and lath should be cut to create a true plane of expansion. Consult a stucco representative for proper placing of control joints. 

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.

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.

The standard size for a brick is normally considered to be the modular brick which is 3.625 wide x 2.25 high x 7.625 long. Call out brick using width x height x length. 

Atlas™ structural brick is a hollow clay brick product that was developed to permit the use of reinforcing to enhance the structural characteristics of brick. Brick is an excellent product to resist compression loads, but often masonry is required to act as a beam or wall to resist earthquake, wind or gravity loads. Reinforcing steel placed in the brick cells is grouted to create resistance to tension. Atlas brick are designed similar to Concrete block but with allowable design stresses 2 to 3 times stronger. For further information on Atlas structural brick see Atlas technical data brochure. 

Curtain wall is a term often associated with glass window framing. With glass, it is commonly understood that the glass has no ability to carry building loads. Wind, earthquake and thermal loads are transferred from the glass to mullions and girts. The brick curtain wall behaves in a similar manner. 

In the brick curtainwall, the brick are supported on the foundation and run past the floors with attachments at the floor which isolate the vertical deflection of the building from the wall. This concept eliminates the need for perimeter floor beams that are designed to carry the vertical load of the brick. The tallest building known to the author is 180 feet. The exterior brick wall is a continuous 180 feet tall, horizontally and vertically reinforced with no ledger angles. For more information see Crittendon. 

The temperatures of the air and the materials - thin brick, adhesive, and the surface to which the thin brick will be applied - must be between 45 degrees F and 90 degrees Fahrenheit. This temperature range must be maintained for 48 hours after the application has been completed. 

Both exterior and interior walls must be rigid (stiff). The maximum variation from plane is 1/8" in 8'0". In Enterior work, vertical and horizontal control joints must be installed every 18 feet or more frequently - not to exceed 144 square feet between control joints.

Expansion joints are placed in brick to allow the cumulative expansion to combine at the expansion joint causing a compression of the joint. Expansion joints are filled with a 50% compressible neoprene material. Expansion joints are generally spaced to accommodate twice the design expansion to allow for the expansion joint material. The expansion joint is typically between 3/8" to 1/2" thickness. 

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.

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. The Technical Notes present the most up-to-date information 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.

Atlas™ structural brick has a compressive strength of masonry f'm of 3000 psi or more depending on the color. The darker the color generally the stronger the brick. This value is compared to a typical design value of 1500 psi for Concrete block masonry. This means that a thinner brick wall can generally carry the same load as a thicker concrete block wall which saves building space and cost. 

Atlas™ structural brick has a compressive strength of masonry f'm of 3000 psi or more depending on the color. The darker the color generally the stronger the brick. This value is compared to a typical design value of 1500 psi for Concrete block masonry. This means that a thinner brick wall can generally carry the same load as a thicker concrete block wall which saves building space and cost. 

The number of brick required per square foot is based on the size of the brick. The larger the brick the fewer the brick required. To determine the number for a wall area, measure the area (Height x Length) of the wall to be covered. To determine how many- thin brick are needed multiply the wall area by the number of brick per square foot. For example: If the height of the wall is 10 feet and its length is 20 feet, the area of the wall is 200 square feet. About seven modular thin brick are needed to cover a square foot, so 200 square feet X 7 thin brick per square foot = 1,400 thin brick to cover the wall. Remember, there will be some losses because of cutting and damage, so order extra thin brick (most installers assume 5% waste). 

The color of a brick is determined by a variety of factors: the blend of clays, the temperature it is fired at, pigments such as Manganese and Chromite, and sometimes slurry coatings poured onto the brick before firing. Flashing is also a firing technique used to alter the color by reducing Oxygen which causes incomplete combustion in the kiln causing a darker shade to the brick.

Thin brick can be treated with water repellents in the same way they are applied to full thickness veneer brick. See Interstate Technical bulletin for recommendations. 

Atlas™ brick have special coring called cells that allow them to be reinforced and grouted as required by design. Those cells that are not grouted can be insulated using foam beads, Styrofoam inserts, and poured in expanded insulation. See the Atlas™ Technical Data Brochure for insulative values for various insulations. 

The model energy code requires an R-value of 5.7 for masonry walls for schools, offices and other buildings. When greater resistance to heat loss is desired, an integral pilaster design which consists of two wythes of brick separated by an air space with rigid insulation filling the  air space. This gives a rigid surface on both the exterior and interior wall. When a soft wall (drywall) is desired, rigid insulation is placed on the back of the brick and light gage framing studs are placed behind that to support the drywall. Flashing runs through the brick to the back side of the insulation and up the back of the insulation. Use closed cell extruded polystyrene insulation. 

Use over clean, sound, dimensionally stable masonry or concrete. If the walls are wet, the water source must be discovered and eliminated. Painted concrete should be brush hammered or heavily sand-blasted. Concrete and masonry surfaces should not vary more than 1 /4" in 8 feet. 

Expansion and control joints in a masonry or concrete substrate must be mirrored in the thin brick. If a metal lath is used, it must be cut at the expansion joint. Mere the thin brick system meets other materials, flashings must be installed to direct the flow of water clown and out. Do not rely on caulking. 

It is good practice to install a wire lath. Use galvanized or stainless steel wire lath for all exterior applications. 

Apply the scratch coat of mortar on top of the wire lath, masonry or concrete. Float surface of the scratch coat plumb and true and allow to set until firm. 

Apply the setting coat with the straight edge of the trowel, and then the notched edge of the trowel should be used to groove the coat just prior to installation of the thin brick. Then use the notched edge of the trowel to groove the setting coat just prior to installation of the brick. 

Backbutter or apply a setting coat to the back of the brick. 

Space thin brick 3/8" apart. Beat the brick firmly into position with a beating block or rubber mallet. All edges must be sealed with mortar so that there are no voids between the brick and the wall. 

Joints must be free of dirt, debris or spacers. Sponge or wipe dust and dirt from thin brick faces. Press the mortar into joints with a tuck-pointing tool so that they are full and free of pits and voids. Tool joints when recommended by mortar manufacturer. Use a masonry joint tool, screwdriver or other suitable implement. Keep the jointing tool clean and damp.

Install gypsum wallboard or concrete board to the exterior face of the studs 

Install a water resistant membrane on top of the wallboard. Lap and seal joints according to the manufacturer's instructions. Because the thin brick system forms the weather barrier for the structure in exterior applications, proper application of the water resistant membrane is mandatory. 

Install a wire lath over the water resistant membrane. Use galvanized or stainless steel wire lath for all exterior applications. In exterior applications, where the thin brick system meets other materials flashings must be installed to direct the flow of water down and out. Do not rely on caulking. 

Apply the scratch coat of mortar on top of the waterproof membrane and metal lath. Float surface of scratch coat plumb and true and allow to set until firm. 

Apply the setting or brown coat with the straight edge of the trowel, and then the notched edge of the trowel should be used to groove the coat just prior to installation of the thin brick. 

Backbutter or apply a setting coat to the back of the brick. 

Space thin brick 3/8" apart. Beat the brick Firmly into position with a beating block or rubber mallet. All edges must be sealed with mortar so that there are no voids between the brick and the wall. 

Joints must be free of dirt, debris or spacers. Sponge or wipe dust and dirt from thin brick faces. Press the mortar into joints with a tuck-pointing tool so that they are full and free of pits and voids. Tool joints when recommended by mortar manufacturer. Use a masonry joint tool, screwdriver or other suitable implement. Keep the jointing tool clean and damp. 

The need to control moisture is dependent on the location of the project. In humid climates the flow of moisture moves toward the interior as a higher humidity exterior moves water to low humidity interiors. In low humidity exteriors and high humidity interiors the flow is to the exterior. Couple this with environmental concerns such as rain or snow and the issues are complex. Because of this, it is important to involve a mechanical engineer to assess the dynamics of the wall system. 

In low rainfall climates, single wythe applications may behave without any problems. In high rainfall climates, the Atlas™ wall may require a drainage system consisting of vapor barriers and flashing. Contact your Interstate representative for more information. 

Unfortunately, there is no national database of brick colors and textures. However, a local brick distributor representing a wide variety of manufacturers will probably be able to match your brick if it is still manufactured. A good brick salesman will know which brick in his stock comes closest to yours. This web site also has links to manufacturers many of whom have brick displayed on their web site. For names of local brick manufacturers and distributors, see your local Yellow Pages under "Brick". 

The reason concrete block cracks is primarily due to the fact that concrete shrinks when it dries and expands when it gets wet. If you consider the dynamics of concrete, water is added to concrete in forming the block units upon curing or hydrating, the block shrinks. When the block are placed in the wall, water is added to the mortar which transfers to the block while they are wet which causes additional expansion. Grout may also be added to the concrete block which also causes expansion. This compresses the mortar joints while they are wet. From this point the wall begins to dry and as it does it shrinks. As the block shrinks, it pulls away from the surrounding materials which are also block. As these units dry together, the cumulative shrinkage creates forces in the block which exceed its internal tensile strength capabilities. Once this happens the units crack. Control joints are placed in the block at intervals of 30 ft. or less in an effort to keep the stresses localized forcing the crack at the control joint. Atlas™ brick on the other hand begin expanding as they exit the kiln. This is the smallest the brick is during its life. Brick are comprised of clays and with moisture these clays expand. Some shrinkage occurs with cold temperatures, but the predominant direction of movement is expansion. Instead of pulling itself apart as in the case of concrete block, the brick push on surrounding brick compressing all of the mortar joints making them more water tight. Cracking generally occurs at corners where the long wall tries to push the attached adjacent wall bending the corner and forcing tension at the corner which causes a crack if reinforcing isn't placed in the brick to take the tension. Expansion joints are placed in the wall to help prevent this cracking. See FAQ: " What are expansion joints?" for more information on this subject. For this and other reasons brick walls are more water tight than concrete.

In some brick, the color of the brick is defined by adding a pigment to the clays before firing. Other times a coating is poured onto the face and sides of the brick. In addition, the temperature of the kiln and the combustion in the kiln will create other colors. With many brick a change in firing temperature of 50 degrees will change the color of the brick. Brick are generally fired between 1900 and 2100 degrees Fahrenheit. 

Because of the shrinkage associated with clay during the drying process, we have not been successful at making a solid bond beam unit. These are most commonly placed as lintels for windows, doors and other openings. Instead, Interstate suggests using soldier courses at the lintel location. (See page 14 of the Atlas Technical Data Brochure under Special Reinforcing).

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 backside 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.

Atlas™ brick and Concrete block can be used together so long as both material properties are considered. Because Concrete block is a cementitious product and shrinks upon drying, control joints should be placed in the walls to accommodate the block shrinkage. The Atlas™ brick's primary movement is expansion which acts as a restraining element against the block. This restraint may create greater tension forces in the block which could cause shrinkage cracks to occur at more frequent spacing. 

Because Atlas™ are 2 to 3 times stronger than block, use block design stresses when combining both materials. Because of this, Atlas™ can replace a CMU building with little changes. Contact the manufacturer for suggested considerations. 

Brick is an all-natural building material that is made from a mix of clay and water that is then baked, or "fired," in a kiln until hardened. Different clays produce different colors, and there are many different types of clays. In addition, various natural coatings, such as sand and limestone, can also be added during the firing process to produce different colors, effects, textures and finishes. Even a brick's position in the kiln can affect the final look. When you combine these with the tonal varieties of today's mortars, you can see that your color choices in brick are virtually endless.