Editor's note: This special edition of Troubleshooting is occasioned by a letter we received a while back from a Michigan architectural firm. The letter contended that the development of the cavity wall system has made masonry more complicated, more expensive, and more prone to problems than it was when solid walls were the norm. It suggested that a return to solid wall construction might be a good idea, and asked what problems such a plan might involve. We forwarded the letter to members of our editorial advisory board and asked for their opinions. Here, we're publishing excerpts from their responces.
Our company provides architectural services on jobs typically ranging from $5 million to $50 million. Masonry has traditionally been one of our chief material resources. Prior to the '60s, it was used as a matter of course with little concern for details. The mason knew what to do to make a wall work. Specifications were very detailed with few changes from job to job. Problems related to masonry construction were virtually nonexistent. With the development of cavity wall systems in response to the energy crunch of the mid-'60s, problems with water leakage, efflorescence, cracking, and movement increased dramatically. Members of our firm have spent many hours trying to improve our knowledge of masonry materials and how to use them. We believe we are on the cutting edge of the current technology, but now find the masonry wall to be expensive, hard to build, and highly dependent upon the technique of the mason. It requires intense supervision to assure that all of the elements are installed and in the proper order. For some time, the company's "Old Timers" have asked, "Why not return to the masonry walls of old when they didn't have all of these problems?" At first, we had all of the answers for them, but now we are wondering the same thing ourselves. When circumstances permit, we are proposing to build an exterior wall without an insulated cavity and provide the insulation, vapor barrier, and plaster on the inside wall surface. We don't intend to abandon the cavity wall in applications where it is the logical choice. We will still have flashings, weep holes, movement joints, anchors, and the like, but things would be much simpler again. We recognize that masonry materials are made differently today than they were years ago. We also realize that differential movements will be a great concern. Do you foresee any additional problems with returning to a masonry system that served us well for many years? Dick Sedlecky
Grand Rapids, Mich.
Changes in the masonry industry have been motivated by our desire to provide masonry that is competitive with alternate systems. The massive brick walls of yesteryear have given way to the thin masonry segments of today. Part of this resulted from the energy crunch you describe: we now need to provide structures that are more economical to heat and also to conserve the energy used during brick manufacture. The cost of labor is a factor also. Cavity walls are less labor-intensive than massive barrier walls. Recent interest in renovating old masonry structures and reusing them for other purposes has given us a chance to evaluate one consequence of the construction you describe. Insulation and vapor barriers have been added to the inside of barrier walls to provide interior climate control in keeping with modern standards. The insulation reduces heat flow through the masonry and the once heat-dried masonry is now completely at the mercy of the elements. Too frequently, the masonry units considered durable are now deteriorating due to freeze/thaw exposure. The vapor barrier counteracts the effect of adding moisture to the interior by abating its passage into the masonry segments. I am not sure how you anticipate returning to the masonry of yesteryear. Remember that products such as cement, lime, and units have changed; test procedures for evaluating products have evolved to reflect changing conditions; and today's labor costs are different. With change, one must question all aspects of the composite. Albert W. Isberner, Jr.
Consulting Materials Engineer
Both solid walls and cavity walls have advantages and disadvantages and the use of either type depends on what the designer is trying toaccomplish. According to Harry Plummer's 1950 and 1962 editions of Brick and Tile Engineering, cavity walls had been used extensively in the United States for 30 years (since sometime between 1920 and 1930). Based on these dates, I would hardly call cavity wall construction a new untried concept. The features generally stressed for cavity walls are their resistance to rain penetration, which results from complete separation of inner and outer wythes, and the thermal insulation provided by the cavity between the wythes, either as an air space or filled with suitable insulating material. Solid walls generally have higher strength. Neither type rates highest in all respects.
Table 1. Relative ratings of
cavity and metal-tied walls
Wall Cavity Metal-tied Rain
1 2 Thermal
1 2 Sound
1 2 Fire
S S Compressive
2 1 Transverse
2 1 Cost 2 1
Table 1 from Plummer's book shows relative ratings for both types of walls. In the table, rating 1 is superior to 2, and S indicates the same rating.You seem concerned that the cavity wall is too hard to build and has problems with cracking, water leakage, and efflorescence. But a properly designed wall with good workmanship should not have any of these problems. Both types of walls are sensitive to workmanship. In fact, it is the single most important ingredient to success. Solid walls not well constructed leak as much as poorly constructed cavity walls. The industry evolved the insulated cavity wall to overcome moisture problems inherent in the solid wall. Both types of walls need good workmanship to be successful, but the cavity wall provides better water resistance, thermal insulation, and sound transmission. The solid wall may be preferable for taller walls for which height is the governing factor. Seymour A. Bortz
Wiss, Janney, Elstner Associates Inc.
Multi-wythe walls of the past worked as mass or barrier walls. They stopped the inward migration of water by absorbing water or providing many barriers to water penetration. They typically were not insulated and did not contain vapor barriers. The walls could absorb considerable water without causing damage. Because no vapor barrier was provided, moisture entering the walls would dissipate either to the interior or to the exterio