Masonry Magazine December 1963 Page. 20
The Contemporary Bearing Wall
(Continued from page 11)
winter enclosure. It illustrates how the working area, as well as the masonry wall is protected. Heating units can be placed on the scaffold.
Figure 10 shows winter enclosure using tubular scaffold. At least one manufacturer provides a canted purlin for topping the enclosure. This allows drainage.
Polyethylene films are commonly used as enclosure materials. However, unless they are very thick, they are quite easily torn by the wind and need constant repair or replacement. Canvas tarps with grommets make good enclosures when properly anchored but do not provide daylight for the working area. The best solution seems to be a combination of opaque and clear materials. There is a considerable amount of solar heat gain within the enclosure on sunny days when clear materials are used.
Best results with clear or translucent plastic materials are gained when the plastic is reinforced with nylon or other fibers to strengthen it. While the cost of the material is considerably greater, the increased durability and lower maintenance should justify it.
Wind is the greatest enemy of winter enclosures. Careful attention must be given to proper bracing and connections to allow the scaffold to resist wind forces.
It seems apparent that considerable study is required to provide a proper solution for the protection of story height work in multi-story wall-bearing construction. It is hoped that work in this area will be pursued by the manufacturers of tubular scaffold.
The use of admixtures or antifreezes to lower the freezing point of mortars is not recommended. Such materials in amounts large enough to lower the freezing point of mortar significantly would result in a serious reduction in the strength of the mortar. Salts in these antifreezes will also contribute to efflorenscence.
Calcium Chloride may be added to the mortar to accelerate hydration during the protection period. However, it must not be added in amounts greater than two (2) percent of the portland cement by weight. When used it should be added to the mixing water and care must be taken to avoid high temperatures of the water. This combination can cause rapid setting of the mortar (flash set).
MISCELLANEOUS
The increased use of wall-bearing construction in high-rise buildings has aroused considerable interest among material and equipment manufacturers.
One significant development has been the prefabricated stair system. It is amazing, to say the least, to observe a job at its beginning with steel stairways rising five or more stories in the air before masonry work has begun (Fig. 11). These stair systems provide excellent masonry guides for story height coursing and provide considerable economy in the overall construction operation.
Other innovations are now beginning to appear on the construction scene. As greater design acceptance is given to true wall-bearing construction, new developments in construction techniques will encourage more true structural use of clay masonry.
Many structural designs will undoubtedly include both reinforced and unreinforced brick masonry. Reinforced brick masonry (RBM) can replace other structural materials and result in more work for the mason contractor (Fig. 12). The revival of wall-bearing masonry will certainly stimulate its use in all areas of design.
See Next Month's MASONRY
For Part III- Contemporary Bearing Wall Series
MASONRY
December,