Q: Plans for a new building specify a 4-inch-thick, 10-foot-high screen wall around an outdoor garden. The drawings show the concrete masonry wall is not to be reinforced. This seems a bit high to me for a nonreinforced wall. Are there standard design requirements for screen walls?

A: You are correct. A 4-inch-thick, nonreinforced concrete masonry screen wall should not be built higher than 6 feet, 8 inches unless it is supported laterally in the horizontal or vertical direction every 6 feet, 8 inches. The National Concrete Masonry Association technical note (NCMA-TEK 5) gives the maximum spacing of lateral supports for different screen walls. The supports must be provided at these spacings in the vertical or horizontal direction, but not necessarily in both directions. Lateral support may be obtained from steel channels or beams or reinforced concrete masonry pilasters. If lateral supports are not provided, concrete masonry screen walls cannot be built higher than the distance allowed between lateral supports.

Minimum Thickness and Maximum Span
for Concrete Masonry Screen Walls
Construction Minimum
Nominal Thickness of Walls
4" 6" 8"
Maximum Distance Between Lateral Supports
Exterior 4" 10' 0" 15' 0" 20' 0"
Interior 4" 16' 0" 24' 0" 32' 0"
Exterior 4" 6' 8" 10' 0" 13' 8"
Interior 4" 12' 0" 18' 0" 24' 0"
Reinforced* 6" NR** 12' 6" 16' 8"
Nonreinforced 6" 9' 0" 12' 0"

*Total steel area, including joint reinforcement, not less than 0.002 times the gross cross-sectional area of the wall, not more than two-thirds of which may be used in either vertical or horizontal direction.**Not Recommended.Source: "Concrete Masonry Screen Walls," NCMA-TEK 5, National Concrete Masonry Association, 2302 Horsepen Red., Herndon, VA 22070.