THINK SYSTEMS

by Jason Yana

A Guide to the Design & Detailing of Masonry Wall Systems

A Systems Approach

To successfully design and build masonry cavity walls and veneers, one must take a systems approach. A masonry wall is an organized assemblage of interdependent parts which work together to form a building envelope. The wall may be made of a combination of clay brick, concrete masonry units, stone, calcium silicate units, etc. The backup may be concrete masonry, wood frame construction, steel stud construction, concrete, etc. A good designer should know the intricacies of each material and what detailing implications those characteristics may require. This document is intended to aide the designer to make these decisions for some of the more common masonry wall systems used today.

Anchorage

All masonry veneers must be laterally anchored to the structural backup. Corrugated ties, adjustable anchors , and horizontal joint reinforcement are all examples of anchoring devices. Building codes require the architect to indicate specified type, size and spacing of all ties and anchors on the project drawings. Since the architect is responsible for the design of the anchorage strategy, she would be wise to understand the intricacies of veneer anchorage.

Movement control

All materials will undergo dimensional changes over time. The degree of expansion or contraction varies with the material in question. Brick, for example, is fired in a kiln and is as small as it will ever be. Once installed, a brick will undergo a slight degree of irreversible moisture expansion. Conversely, concrete masonry is cured by hydration, and will shrink over time. To control this shrinkage in concrete masonry, hot dipped galvanized joint reinforcing is set in bed joints at 16" o.c. vertically. Control joints are created to control cracking in concrete block while expansion joints are placed in brick walls to allow expansion.

Moisture Control

All 4" unreinforced masonry veneers are expected to allow some wind driven rain to penetrate, most likely through hairline cracks between brick and mortar. For this reason, an airspace is designed between veneer and backup to allow moisture to drain down the cavity and exit at flashing and weep holes. All of these systems require proper flashing details to perform correctly. See "Flashing...Tying the Loose Ends" published by the Masonry Advisory Council for more information on flashing details.