Masonry Magazine June 1980 Page. 18
Walls can be calculated easily using the procedure given in Technical Notes 4 Revised, "Heat Transmission Coefficients of Brick Masonry Walls", or the ASHRAE Handbook of Fundamentals. The mass of the brick veneer provides the capacity insulation. It effectively lowers and delays the peak heating and cooling loads. The overall U value obtained for the wall assembly can be adjusted by the capacity insulation correction factor (M factor) given in Fig. 1 of Technical Notes 4B, "Thermal Transmission Corrections for Dynamic Conditions-M Factor". This adjustment of the overall U value will help the designer to more accurately predict the performance of the building envelope. The actual performance of brick masonry buildings shows that this adjustment is very conservative, but it is an improvement over the steady-state assumptions normally used in calculating heat flow.
Acoustical Properties
Brick veneer wall assemblies reduce sound transmission by two means. The mass reduces sound transmission by absorbing the energy of the sound vibrations. The discontinuity of construction prevents vibrations of the exterior brick wythe from directly vibrating the rest of the wall assembly, thereby retarding sound transmission to the interior.
Although there are no specific data available on the sound transmission characteristics of brick veneer wall assemblies, the brick veneer wall system shown in Fig. I has an estimated STC of 40 to 44. See Technical Notes 5A, "Sound Insulation-Clay Masonry Walls", for more information on the Sound Transmission Classification (STC).
SELECTION OF MATERIALS
# Brick
The brick for veneer should conform to ASTM C 62 or C 216. Because the brick wythe is isolated from the remainder of the wall, Grade SW is recommended when the brick masonry is to be used in freezing climates. The brick selected should have an average initial rate of absorption (suction) of not more than 30 grams per 30 in. (19 355 mm²) per minute. If the suction exceeds 30 grams the brick should be properly wetted prior to laying. Technical Notes 11B describes the procedure for wetting of brick.
The use of salvaged brick is not recommended. In general, masonry constructed with salvaged brick is weaker and less durable than masonry constructed with new brick. Salvaged brick is discussed in Technical Notes 15.
# Mortars
Portland cement-lime mortar is recommended for brick veneer because its performance usually is better and more predictable than that of masonry cement mortars. Many masonry cements contain air-entraining agents or other ingredients which sacrifice good bond for workability, color, etc. See Technical Notes 8 Revised, "Portland Cement-Lime Mortars for Brick Masonry", for information on portland-cement lime mortars.
Type N mortar is suitable for most brick veneer, however Type S or Type M may be required. Type S mortar is recommended where a high degree of flexural resistance is required and Type M is recommended where the brick veneer is in contact with earth. For further information on the selection of mortar, see Technical Notes 8B, "Mortar for Brick Masonry-Selection and Control".
Anchors and Ties
Empirically designed brick veneer is usually supported on the foundation with lateral support being provided by the ties and backup system. The ties providing the lateral support for the veneer must be capable of resisting tension and compression resulting from forces perpendicular to the plane of the wall, but permit slight vertical and horizontal movement parallel to the plane of the wall. Attachment of brick veneer to the backup system, which permits differential movement of the veneer and the backup is discussed in Technical Notes 18 Series.
The selection of ties depends on the backup system. Typical ties are shown in Fig. 2.