Effect of spatial variables on bricklaying productivity and ergonomics.

Abstract

This research demonstrates that spatial variables in the bricklaying environment can have significant impact on masons' productivity and ergonomics. Spatial variables considered were distance above the work surface on which the mason stands and distance to either side of the brick and mortar supply. Seventy-four masons completed a bricklaying ergonomic questionnaire that asked masons to indicate their perceived discomfort, perceived speed, and material layout preferences for different vertical locations in a brick wall. Ten bricklayers constructed ten brick veneers, each 13'-8 wide and as high as they could physically reach, which varied from 5'-7 to 6'-8. Time spent installing all bricks was recorded and quality of completed veneers was measured at different vertical and horizontal locations in the brick veneer. The questionnaire showed that masons' perceived discomfort and likelihood of developing musculoskeletal injuries in the back and upper extremities were greatest when bricklaying was done above shoulder height and below knee height. Masons generally preferred a material supply at wrist/hand height throughout construction of an entire wall. Analysis of vertical distance showed that masons had the highest productivity about 1'-7 to 4'-0 above the working surface. Productivity decreased significantly above and below the 1'-7 to 4'-0 range. In comparing the upper and lower extremes, masons were more productive working down low than working up high. Analysis of horizontal distance showed masons' productivity was not as sensitive to horizontal distance as vertical distance. Results showed that the central section of the veneers, near the material supply, had the highest productivity. Productivity was lower in the left and right extremes of the veneers, which ranged from 3'-8 to 6'-4 from the center of the material supply. Inspection of quality of constructed walls showed that deviations in head joint and bed joint thickness, horizontal and vertical levelness and alignment of bricks, and rotation of bricks were greatest in the upper-most and lower-most courses in the veneers. Overall results showed that avoiding or minimizing bricklaying in the upper and lower extremes of walls reduces masons' levels of perceived discomfort and musculoskeletal problems, increases masons' satisfaction by accommodating their preferences, increases masons' productivity, and increases masons' quality of work.