The Benefits of 6-inch-wide Masonry Units

Brief 

Rising material costs have made 6-inch-wide concrete masonry units an attractive option for interior and exterior wall construction for schools or mixed-use and residential properties, Philippe Ledent writes. Ledent covers many of the benefits of 6-inch CMUs, including optimal fire resistance and sound transmission.

Insight

In terms of structural concrete masonry unit (CMU) construction, the predominant unit sizes are nominally 8-inch and 12-inch-wide units. However, with rising material costs, 6-inch-wide units are ideal for interior and exterior wall construction depending on wall heights and design loads.

In terms of interior partition walls, ungrouted and unreinforced CMU wall construction is often the most cost-effective solution compared to other building systems. In addition, CMU construction provides superior fire resistance and sound transmission performance.

Unreinforced masonry partition walls are typically designed for lateral forces prescribed under the International Building Code (IBC) and the American Society of Civil Engineers’ Minimum Design Loads and Associated Criteria for Buildings and Other Structures (ASCE 7).

These lateral loads typically include a minimum horizontal load specific to interior walls and partitions included in IBC Section 1607.15.

IBC Section 1607.15 Interior walls and partitions. Interior walls and partitions that exceed 6 feet (1829 mm) in height, including their finish materials, shall have adequate strength and stiffness to resist the loads to which they are subjected by not less than a horizontal load of 5 psf (0.240 kN/m2).

Relative to the partition lateral load, recommendations are provided in The Masonry Society’s (TMS) Strength Design of Masonry publication. “There is not a direct strength load combination that addresses the partition load.

Use 0.9D for flexural tension to be consistent with other strength load combinations where the dead load is acting as a ‘resistance’ and use 1.6 as a load factor for out-of-plane partition load (live load).”

Based on this minimum interior wall and partition horizontal load, a maximum wall height is calculated based on the mortar type specified and the density of the masonry units.