Masonry Magazine April 1965 Page. 24
Contemporary Bearing Wall
(continued from page 23)
into the ground in a series of lines or paths rather than in point loads as occurs in structural frame buildings.
Wall Types and Details
Almost all commonly used masonry walls have some loadbearing ability. However, in order to fully take advantage of the bearing-wall system, high strength masonry materials such as brick or heavy duty structural clay tile are required. Bond beams are desirable at wall and floor junctures to receive and transmit stress. It is absolutely necessary that the construction details provide structural integrity for this system. The floors and walls must be joined so that they will work together each giving support and bracing to the other.
The problem of keeping water out of the building may be somewhat more severe than in our widely used curtain or panel wall constructions with cavity walls. It is not, however, insurmountable. With careful, waterproofing and systems of flashing and drainage can be provided. Cavity or masonry bonded hollow walls can be used which provide water drainage channels. These cavities can be insulated if desired. Often, these hollow spaces are desirable in the interior walls to accommodate mechanical equipment.
Bond breaks should be provided whereever possible between concrete floors and masonry walls. Usually there will be sufficient frictional resistance to meet the structural requirements. Metal ties may be used to bond the wythes of the wall together. Tests indicate that strength is maintained while resistance to water penetration and ease of construction are improved. Cost is often reduced.
Economics
Bearing-wall buildings are often more economical than structural frame buildings. This is particularly true when the building is such that there are repeating walls and partitions with floor spans less than 40 feet and when the floor plan of each story is much the same. The savings come about primarily through elimination of the structural frame. But also contributing is the simplicity of constructing these buildings in which elaborate formwork is eliminated.
Cost studies have been prepared on a typical bay of a 6-story building. This bay was designed and cost estimated for steel frame, concrete frame and brick bearing wall structural systems. In this comparison it was assumed that the structure was an apartment building. Included were the structural elements of the building and their interior finishes, as well as exterior walls for the bay. The costs have been reduced to equivalent costs per square foot of floor area. It was found that the steel frame superstructure cost $3.02 per square foot of floor area, the concrete frame superstructure cost $2.96 per square foot of floor area, the 8-inch brick bearing walls, exposed both sides, cost $2.81 per square foot of floor area, and the 6-inch brick bearing walls would be $2.77 per square foot of floor area. The masonry solutions could be further reduced by using larger sized units. Savings in excess of 8 per cent were found for the 6-inch bearing wall solution versus the structural steel frame system.
These figures are theoretical, actual figures are always more conclusive. In the 1950's, the Corps of Engineers offered alternate designs on a standard dormintory; one being a concrete frame dormitory with walls and partitions built of concrete block exposed and painted. The second being a brick building with brick and tile loadbearing cavity walls and loadbearing tile partitions. The contractor bidding these dormintories offered a lower price in 49 out of 53 of them on the leadbearing alternate.
The construction of loadbearing buildings is easy and relatively simple compared to that of a structural frame building. And, surprisingly enough experience has been that in many cases these buildings go up faster and offer earlier occupancy than do structural frame buildings. The construction of tall bearing-wall buildings is much like building a one-story building over and over again. The walls are built, the floor is poured or placed, and a one-story building is built on top of that. The scaffolding is simple, ordinarily requiring only one lift per floor height. So that, in effect, for half the wall height the mason is working off the floor. Scaffolding like that used for a single story residence is suitable in many cases. Overhand laying of brick is suggested to avoid scaffolding the outside of the building. There are other developments such as prefabricated metal stairs which assist in the construction of loadbearing buildings. The stairs are set before the walls are started and the landings become bench marks for the floor construction.
Brick masonry in conjunction with small amounts of reinforcing steel can span large openings. Such reinforced lintels offer lower maintenance costs, eliminating painting of exposed steel and additional safety because the reinforced brick lintel has built-in fire proofing.
Examples
Some of the U. S. designers, who have done brick bearing buildings in the last few years, include Weese & Associates, Chicago. They have designed schools in Chicago and Columbus, Indiana, in which bearing walls and brick piers carry the loads.
Architects Collaborative of Boston have designed several bearing-wall dormitories in recent year. One is 8 stories in height, located at Brandeis University.
Hugh Stubbins & Associates also of Boston have designed bearing-wall dormitories for Princeton University.
Colorado Architect, William Muchow, has a handsome bank building with two-story bearing piers in Loveland, Colorado.
St. Louis Architects, Hellmuth Obata & Kassabaum, designed Our Lady of The Snows Housing For The Aged using brick and structural tile bearing walls. One of the buildings is 5 stories tall.
Curtis & Davis of New Orleans used 10-inch reinforced brick masonry bearing walls with a clear span of 15 ft. 4 in. on their New Orleans church, St. Francis of Cabrini. Reinforced brick masonry and shear
About the Author
James G. Gross
James G. Gross, Director of Engineering and Technology for Structural Clay Products, is a graduate of North Dakota State University with a degree in architectural engineering. He worked for three years as a field and staff engineer before joining the national office as a staff engineer in 1957. In 1961 he was named Associate Director and in November of 1963 he was promoted to his present position. He is co-author of "The Ultimate Cost of Building Walls", a report which has been widely used by the construction industry.