Masonry Magazine February 1982 Page. 33
SILLS
When prefabricated brick, pre-cast concrete, or stone sills are used, they should have section lengths as long as is practical. The lengths will be determined by ease of handling and erection and the sills' ability to resist erection stresses. The length of sill sections should be limited to a length that can easily be handled by equipment already on the jobsite. The joints between long sill sections should be constructed using a soft joint. It may also be necessary, in very long runs of sill, to provide expansion joints at the ends where the sill abuts the jamb.
SOFFITS
# General
Detailing of soffits for brick masonry requires special considerations. The primary function of a brick masonry soffit is to enclose the building while providing an esthetically pleasing appearance. There are two primary considerations in addition to esthetic value in the detailing of soffits: the structural stability of the system and whether it can be easily and economically constructed using conventional methods.
Though prefabrication has not been widely used for total projects, it has been successfully used in many specialized applications and is considered a conventional construction method. Prefabrication has been widely used in the construction of soffits and may provide the most economical approach on certain projects. Construction of soffits in place often requires expensive forming and shoring. However, if there is only a small area of soffits involved on a given project, this may be the most efficient method.
# Materials
Soffits generally are reinforced and grouted in some manner, whether built in place or prefabricated. Several projects have been constructed using reinforced and grouted hollow units, conforming to ASTM C 652. See Technical Notes 17 for information on reinforcement and grout. Properties for brick and mortar are discussed in Technical Notes 7B.
There are several high bond mortar additives available which may allow the designer to eliminate the reinforcement and grout. However, it should be noted that the high bond mortars do not work well with all brick units. The instructions of the additive manufacturer must be strictly followed, and a pre-design testing program should be carried out, see Technical Notes 39A.
Design
There are several questions which must be answered when designing soffits. Some deal with esthetic value, some with structural stability and some with construction. The primary esthetic concern is configuration. Should the soffit be horizontal, or sloped, should it be integral with the spandrel or separate? The primary design concern is structural. How should it be detailed to assure structural soundness, under all loading conditions, including any loads imparted during erection? This may require detailing and construction practices unfamiliar to the designer and contractor since this is not like a wall and demands careful consideration. One of the earliest decisions to be made about the construction of the soffit is whether it will be best to construct it in place, or to prefabricate it. The configuration, structural and economic considerations may dictate the method of construction to be used. See Figs. 7 and 8.
Details
General. Each soffit entails its own unique detailing problems. These may include: configuration, support available from the surrounding structure, space restriction on built in place soffits and construction sequence.