Rain Resistant Architectural Concrete Masonry

Integrally colored concrete masonry is commonly used as an architectural material in the Pacific Northwest. By combining different block sizes and shapes, colors or surface treatments, architects have designed many striking buildings. The interest in architectural block led to the development of industry recommendations for rain resistance. This updated technical note addresses the design and specification of a concrete masonry wall system for the western portion of the states of Washington and Oregon where rain resistance is a major concern. Some of these recommendations may not be applicable to the more arid regions of the Northwest.

This publication focuses on weather-exposed, single-wythe concrete block walls. These walls are assumed to be coated with a clear water repellent rather than an opaque coating for aesthetic reasons. They are designed as barrier walls and reinforced and grouted to withstand the forces of wind and earthquake, making the use of internal wall flashing impractical.

Smooth-Face Architectural Concrete Masonry

Architectural concrete masonry units (CMU) are available in a wide variety of sizes, shapes and surface treatments. Integral color can be added to concrete masonry units further increasing the design potential. Integrally colored concrete masonry block units provide a long lasting, low maintenance, attractive finish to masonry structures.

A proper understanding of the benefits and limitations of integrally colored CMU can assist in meeting satisfactory expectations for the finished masonry wall assembly. This will help to avoid possible disappointment in the wall’s appearance.

Concrete Masonry and Sustainable Design are a Natural Fit

The sustainable building movement has gained momentum over the past several years. Rating systems such as LEED and Green Globes have helped to drive this movement. Masonry materials can contribute significantly toward rating system compliance. (See Figure 1.)

Now we must consider the implications of new green building codes that are being developed. ASHRAE/USGBC Standard 189.1 has been published as has the International Green Construction Code (IGCC). At times there have been unintentional consequences of using the rating systems. Most notably, in their misapplication in the form of requirements rather than providing guidance. Codes and standards on the other hand are legal documents with mandatory provisions that can be directly adopted by a city or state government.

Control Joints for Concrete Masonry Crack Control

Cracking in buildings normally results from restrained movement. This movement may originate within a building material due to temperature change or shrinkage or may result from movement of adjacent building elements. In most cases, movement is inevitable and must be accounted for during design if cracking is to be controlled.

Control joints placed in concrete masonry walls are one method of crack control. Control joints are vertical separations built into a concrete masonry wall to reduce restraint and permit longitudinal movement. They are located where cracking is likely to occur due to excessive tensile stress.

For more information, see our Tek Note below, updated April 2023.