Masonry Magazine January 1964 Page. 10
The Contemporary Bearing Wall
(Continued from page 9)
The system will bog down. Too often, completion schedules given by the contractor are unrealistic and are based upon satisfying the architect or owner at the time the contracts are let, rather than on a thorough analysis of job scheduling.
Whether the mason contractor uses the CPM aproach or not is academic. It is vitally important to his success, however, that he study carefully the requirements and operations of each job before it is begun. He must be able to schedule the operations, select the proper crew for each job, schedule delivery of necessary materials as they are required, and keep these materials supplied to his crew when and where they need them. The successful contractor is the one who carefully plans and organizes his jobs in advance and provides proper supervision to see that they are completed as planned.
SUPERVISION
Good job supervision by qualified people is a most essential part of the successful contractor's operations, no matter what type of work is involved. There seems to be a growing tendency, particularly among many of the sub-trades to let the job take care of itself with a working foreman in charge. While the working forman will usually keep the crew busy he normally cannot be expected to run the job with the precision and planning necessary to achieve maximum job economies, the most desirable construction schedules and the quality of workmanship desired. For the mason contractor the bulk of whose jobs are small, the added expense of providing additional supervision probably cannot be justified. However, for the larger jobs, competent daily supervision will more than pay for itself.
In major wall-bearing work, the construction schedule is critical and requires that full time supervision expediate all phases of the masonry work. Much of the superintendent's time should be devoted to close cooperation with the general contractor and with other trades that affect his work, in addition to seeing that the quality of the masonry work is maintained. He must plan for proper storage with protective covering for all masonry materials. It is important to keep units clean and dry. Dirty units will not only affect the appearance of the wall, but they will reduce the brick to mortar bond strength in the wall.
A good masonry superintendent will check the clay masonry units to determine if they should be wetted before they are laid. When there is no information available on the suction or initial rate of absorption of the units, there is a simple field test that can be used. Lay a quarter on the bed surface of the unit to be tested. Draw a circle around the quarter with a grease pencl. With a medicine dropper put 20 drops of water within the circle. The grease pencil line helps to contain the water within the circle. If all the water is absorbed into the brick in 1-2 minutes, the units should be wetted before laying. If not, the units can be laid dry. When the suction of the unit is controlled, the units will lay easier for the mason and better bond will result.
Close supervision is required for the batching and mixing of mortar on the wall-bearing job as emphasized in Section 1. The somewhat crude and inaccurate methods of measuring materials and batching mortar that are used on many jobs can be avoided with close supervision.
It is important to provide for proper protection of the masonry at all times during construction when the masons are not working on the wall. A plank or a few pieces of roofing felt thrown over the wall will not provide proper protection. The best solution is a canvas tarp weighted and draped over both faces of the wall.
Much of the damage to the appearance to masom walls during construction is caused by carelessness. Sc folds should be set far enough away from the wall to all mortar droppings to fall on the ground rather than adh to the wall because bracing is too close. On many jobs is possible to see where each frame height of scaffold v located because of the line of mortar stains. When mas brackets are used this problem is partly solved. However mortar droppings continue to accummulate on the maso foot boards. Good supervision will require that the pla nearest the wall be cleared of mortar each night and tips face down on the inner plank. If the planks are in the normal position with mortar droppings on them, a w driven rain will wash the mortar, dust and dirt on the w.
Quality workmanship assuring completely filled he and bed joints will be specified and required in wall-bear construction. One reason, of course, is to obtain the required transverse and compressive strengths of the wa.
The second reason is that such engineered brick we may, in many cases, involve the use of thinner clay sonry walls than those presently used in loadbearing wo. Good workmanship will therefore be most essential insure the maximum resistence to wind driven rains.
If the job is properly planned by the contractor, the superintendent will have a construction schedule or gra on the job, so that he can check daily progress against the estimated schedule. When a closely coordinated and ti construction schedule is necessary, as is the case with w bearing work, daily control at the job site is a must. U of the Critical Path Method requires that this tight control be accomplished.
Cost control and records are extremely important any job. The system should be developed and set up management. However, no cost system is any better th the records that are kept in the field. A good superint dent will look upon costing as a most important factor every job rather than a nuisance which is tolerated o because management demands it.
SUMMARY
There are many types of buildings in which wall-bear construction will be lower in cost and will make poss the earlier completion of the structure than will skele frame construction with non-bearing exterior curtain panel walls. Structural clay masonry units, with their inherently high compressive and tensile strengths and olumetric stability and particularly ideal for use in eng eered wall-bearing designs either low rise or high r. Because of their greater strengths, properly enginee walls built entirely with clay units can be thinner and be built to greater heights or to more stories than many the combination unit walls currently used extensive. There are available, today, as standard production ite all over the country, structural clay masonry units is variety of designs, sizes and shapes that will permit construction of ecnomical and structurally efficient w bearing buildings. Likewise, improvements in maso mortars and the development of a greater knowledge whate constitutes a better mortar and how to achieve makes the potentials inherent in the more extensive use clay masonry even more possible of achievement.
Providing adquate protection and heat for both the sonry work and the workmen during freezing weather be especially essential in wall-bearing construction. C siderable structural damage can result if the mortar allowed to freeze befoe it has achieved its initial set. provision of such protection in multi-story wall-bea work is not simple and will require considerable study.
MASONRY January, 19