The Utility Wall

Overview

The Utility Wall is the name given to a special type of wall that is technically classified as a Masonry Bonded Hollow Wall in some building codes. The utility brick is a modular unit with nominal dimensions of 4” x 4” x 12” (3 1/2” x 3 5/8” x 11 5/8”) and is used throughout most of the walls.

Section:Utility Wall

Masonry Bonded Hollow Walls are different from Cavity Walls in that wythes of Masonry Bonded Hollow Walls are bonded with masonry headers, as the name implies, while wythes of the Cavity Wall are bonded with wire ties. The headers create an 11 5/8” thick composite wall where both wythes move together when subjected to external forces.

Due to a greater strength in bending, the Masonry Bonded Hollow Wall, or Utility Wall, is allowed a higher ratio of unsupported height (or length) to thickness (h/t) than the Cavity Wall in most empirical building codes. This allows the Utility Wall to qualify as a loadbearing wall in a majority of industrial and commercial buildings, warehouses, and public buildings where high walls are required.

The coursing is typically 1/3 bond for 5 courses and a special bonding, using headers, for the 6th course. The headers are started 24” from the left outside corner on each wall.

Laying out the perimeter dimensions in increments of 4” can help reduce the amount of brick cuts the mason may need to make. As a rule of thumb for a four sided building, make each wall an even number of feet plus 4”; i.e., 21’ - 4”. The same criteria is used for the wall lengths between the control joints. The location of doors and windows, measured from the corners, can be in any length of 4” increments.

Closure brick may be needed depending on the wall length. The distance of the brickwork between doors or windows can also be in any 4” increment. If the building has offsets, then the length of each wall meeting at the internal corner should be in increments of even number of feet; i.e., 21’ - O”.

The Utility Wall must be supported by an independent footing with both wythes of the wall bearing upon a common foundation. Normal flashing and weephole guidelines should also be used for this wall system.

Utility Walls require control joints (expansion joints) to allow for the change in wall lengths due to moisture and temperature movements without developing stress cracks. For a four sided building, control joints spacing on a straight wall should not exceed 40’ - 4” and 30’ - 4” maximum around the corners. If there are offsets, then the spacing of the control joints around the internal corner should not exceed 29’ - 8”. These suggested lengths may be reduced by one foot increments. Control joints should not be placed alongside a window or door jamb when a lintel supports the brick over the opening.