TYPE OF FACILITY

Dormitory Building

TYPE OF PROBLEM

Cracking and Distortion of Masonry Parapets

SIGNIFICANT FACTORS       

A. Expansion of masonry units due to absorption of moisture
B. Improper detailing
C. Creep strain in supporting concrete framing
D. Poor workmanship

Narrative

This project involved the design and construction of two dormitories for a college campus. The buildings were of twelve and three stories respectively. Construction of both involved a concrete frame (flat plate on concrete columns) with masonry and cavity (brick face and block backup) exterior walls. Each building was approximately 230 ft by 45 ft; the twelve-story building was topped by a 21- by 45-ft mechanical penthouse which divided the roof into two equal parts.

The initial problem which developed was one of distress in the masonry parapets of the twelve-story building.

Upon inspection, it was disclosed that where the parapet "panels" (sections between control joints) were isolated from the building corners and the penthouse (see Figure 3-2a), the parapets were leaning inward as much as 1 in. in the 3 ft from the outer joint where the membrane flashing occurs to the top of the coping.

The parapet masonry was essentially crack-free, although other signs of incipient distress were apparent. These included signs of deterioration at the inboard horizontal mortar joint directly below the coping, which indicated a potential point of weakness for water entry. Some gaps also were noticed at a number of joints along abutting coping stones. A severe crack was also evident at the east end of the penthouse wall from the coping level to the middle of the wall at the first control joint.

At the lower building, the parapets also indicated inboard leaning to the same degree as that evidenced on the larger building. Extreme amounts of efflorescence were noticed on the walls below the flashed joint. Block cells were filled with water and it was noticed, upon removal of one of the coping stones that the membrane flashing ended 1 to 2 in from the inside face of the parapet, thereby exposing block cells rather than covering the block completely and turning downward as a protective lip. Other problems included the fact that, instead of compressible filler running completely through certain control joints as detailed on the plans and specifications, mortar which had been used to set the coping stories made direct contact across the control joints.

The college called upon the architect, the structural engineer, and the contractor to conduct investigations into the cause of the cracking and to remedy the situation at their own cost The contractor immediately .wed an outside expert, who concluded that design deficiencies were the cause of the problems. Various bids for the remedial work ranged from $45,000 to $250,000.

The architect and the structural engineer, working jointly, retained an independent structural engineer to perform tests and prepare a written report detailing the causes of the failures. This report defined the major factors contributing to the masonry distress to the as follows:

1. The improper use of noncompressible filler under the relieving angles
2. The improper filling of the space from the toe of the relieving angle the face the brickwork with mortar

The report of the outside expert concluded that the cracks in the penthouse walls were directly related to these deficiencies. The walls were deemed unable to resist the inward forces generated by the attempted movement of the contiguous parapets, causing the joints to fail in shear and tension.

In regard to the three-story building, the distress was attributed to the narrowness of the installed membrane flashing below the coping. This deficiency, according to the experts, allowed water to enter the cells of the inner block wythe and penetrate the entire parapet construction. After several years of the freeze-thaw cycle, forces developed that caused displacement of the coping and parapet. While a similar construction deficiency (failure to cover the entire width of the parapet with the membrane flashing) was found throughout the taller building, damage from this deficiency was minimal, owing to the use of solid concrete (half) block in the top course directly below the coping. The expert's report concluded that had the walls and parapets been constructed in accordance with the contract documents, there would have been no masonry distress in either of the two buildings.

Meetings were thereafter held with representatives of the college and the contractor. The college representatives indicated that they would not take sides with either the design team or the contractor, preferring that the involved parties work out a solution whereby the damage would be corrected and the cost assumed by the responsible party or parties.

In this instance, no litigation ensued. Continuous meetings resulted in agreement by the contractor to assume full responsibility for repair of defects in the low-rise building. This left the problem of the parapet on the high-rise dormitory.

After numerous meetings, the contractor ultimately admitted that the problem with these parapets may have been attributable, in part, to improper construction.

The college had withheld $17,000 from the contractor under the retention provisions of the construction contract. Consequently, there was a financial stake on the part of the contractor to remedy the condition if he had any intention of recovering this retention. Finally, the general contractor agreed to complete the repair work on the parapet, and to submit a formal claim against the architect for the cost of this remedial construction. This claim sought the recovery of $63,000 for remedial work on the entire project, of which $43,000 related to the demolition and reconstruction of the parapets. To support this claim, the contractor pointed to an expert report he had commissioned which related the parapet distress to permanent moisture expansion of the brick utilized in the buildings. This was directly refuted by the expert retained on behalf of the design professionals. Accordingly, a decision was made to resist vigorously any attempt by the contractor to recover from the architect and engineer. A letter was thereafter written to the contractor on behalf of the architect, stating that his claim was denied in full and that he should expect vigorous opposition to any attempt to recover any of the costs incurred in the remedial work from the architect or structural engineer.

Apparently, this response, supported by expert analysis refuting the contentions of design error, was sufficient to preclude the contractor from pursuing any recovery via litigation. The matter ended with the contractor agreeing to assume all costs of repair.

Technical Analysis

The principal concern in this case was the development of an inward "lean," or stepped displacement, of the masonry parapets (see Figure 3-1) amounting to as much as 1 in. in the 3 ft from the outer joint where the membrane flashing occurred to the top of the coping. The lean is shown in dashed lines and generally developed as an abrupt angle change in those parapet panels (sections between control joints) which were isolated from other restraints such as those at the corners of the roof or the penthouse walls (see Figure 3-2a).

A second concern was the development of a cleavage plane under the coping, a potential point of weakness for water entry (see Figure 3-2b). Longitudinal displacement of the coping (or parapet and coping) of 1/4 to ½ in also was observed.

The contractor alleged that the observed movements were the result of expansion of the bricks due to the absorption of moisture. It is well known that ceramic bodies such as tile and brick (and concrete, as well) expand as moisture is absorbed and shrink as drying takes place. Displacement at corners of buildings and at intermediate changes in direction of walls and the associated cracking of masonry and of spandrel beams and columns are established occurrences.

Cases of up to 3 in of such expansion in a 200-ft length have been noted. This was cited as the cause of the observed horizontal displacement of the parapets and of the coping. Added to this effect would the the creep strain in the columns of the concrete building frame, resulting in a relative upward displacement of the brick facing with respect to the concrete frame, in turn resulting in the observed tilt of the parapets.

The engineers' and architects' representatives agreed that the tilt of the parapets was caused by relative upward movement of the brick facing, with respect to the concrete frame, principally due to creep strains in the concrete columns, perhaps abetted by temperature effects. However, they contested the idea of expansion due to moisture increase as the proximate cause, contending rather, that poor workmanship and improper supervision had resulted in conditions which invalidated the function and purpose of the vertical control joints and the horizontal relieving joints which had been provided in the facing specifically to control the type of distress which had been observed. They showed, for example, the following:

1. The horizontal relieving joints had been built with an incompressible filler, rather than as designed.



2. The functioning of the vertical control joints in the parapet had been invalidated by running the mortar bed under the coping stone through the control joint and by mortaring the control joints over the compressible filler. In some cases, "dummy" joints had been created by having mortar in the control joints, instead of a compressible filler, and applying the joint sealant over the mortar.

Comments

Designers must remember that what is obvious to them may not be understood by contractors and field personnel. Indeed, it is a frequent source surprise to designers to discover how little builders understand of considerations that go into designs. In this case, the control and relieving joints (assuming the allegations of the architect-engineer, as described, are correct) were built in a manner which invalidated their performance. This has to be because the person who built them did not understand their function, and it raises the question of whether or not the contractor (or at least the supervisory personnel) should be expected to understand function. Is the designer looking for blind conformance to plans and specifications (in which case they had best be perfect), or is the contractor a partner in the work? Does an owner buy from a contractor only hours of labor and pounds of material, or is the owner entitled to expect a certain "know how"?

The ideal answer to these questions is clear, The problem is how to get the contractor's input and understanding. One answer is prequalification of bidders. A more positive answer is the presence of the designers' representative on the job -- to a sufficient extent to observe day-to-day operations. This introduces a major problem in the design-construction progression. Many designers are unprepared and/or unwilling to undertake field inspection of their work. Owners are unwilling to support the cost of such an inspection. Both attitudes are understandable, but unfortunate. The observant reader will detect a common thread running through many of the cases in this book: The contractor (neither maliciously nor with intent to cheat or defraud, but out of lack of understanding) doesn't do something, or changes something - and a problem results. In the end, all parties are losers. In the thrashings and flailings of self-protection, everyone is besmirched; recovery of damages, even where clearly justified, is seldom complete and the costs of pressing or defending the suit falls upon all.

It is no answer to say that the contractor should simply follow the plans and specifications to the letter. First, the plans and specifications are seldom letter-perfect. More important, contractors (and the workers) have expenence and good ideas, too, and should the encouraged to suggest timesaving or cost-reducing ideas, and not be precluded from doing so. But the only one fully qualified to judge the merits of these suggestions is the designer. It is a mistake to shut the designer out of the construction process.

Covert violation of the plans and specifications is another matter entirely. Even full-time inspection by an army of inspectors cannot hope to detect every design departure - if the builder is indeed intent on deviation or violation. What is needed is inspection, preferably by someone with at least a modicum of design background (or lacking this, at least in close liaison with the design office), and certainly by someone with the agility to get into close contact with the work and with enough interest and motivation to climb, slog through mud, and endure the occasional physical discomforts which accompany a field job.

A second lesson to be learned from this case is a repetition of the old adage that "the details make the job."

Legal Analysis

Defending the architect in this matter involved negotiations with both the college, on the one hand, and the contractor, on the other. The college took the position that any responsibility for the remedial repair work belonged to the architect and the structural engineer and/or the general contractor. The college specifically refused to take sides or act as a mediator between the involved parties. From the standpoint of the architect, as agent of the owner, this posed a problem, since it gave impetus to the contractor's belief that the owner was not strongly standing behind the design team. Various entreaties to the college were unavailing, notwithstanding the fact that the architect had been commended on numerous occasions for excellence in designing the project.

It therefore became necessary to prepare a detailed analytical construct about the problems at hand and the factors which combined to cause the problems to the buildings. The immediate retention of an outside expert and coordination with the architect and structural engineer developed a dialogue which helped the design team re-create the causes of the failure.

Initial pressure had to be brought upon the contractor to admit that he had failed to use the proper sealant in the control joints and to agree that he would correct this deficiency at his own expense. The contractor was thereafter placed on the defensive, knowing that he had admitted liability to at least one failure. Subsequent meetings resulted in admission by the contractor that insufficient quantities of compressible filter (as called for in the plans) had been available and that he had resorted to asphaltic sealant with the intention of changing the sealant at a later point in the construction. It was pointed out to the contractor that a resident engineer for the architect had noticed, at a lower level of the building's construction, that the wrong sealant was being used. A written memo to the contractor called for the restoration of the correct sealant. It was ultimately discovered that this correction was never made by the contractor for the balance of the building.

This, of course, did create some problem for the architect, since, having once called the contractor's attention to this variance, there was no followup by the resident inspector to ensure further compliance with this request.

A decision also was made to have the outside expect for the architect detail his findings before the contractor, as well as meet with the expert who had been retained by the contractor. In this fashion, the carefully reasoned analysis and findings supporting the design were transmitted to the contractor and his expert for their consideration. This tactic also was designed to impress upon them the fact that any litigation would result in a vigorous defense on the part of the architect, in conjunction with an attack upon the obvious construction deficiencies, one of which had already been admitted.

During meetings with the contractor, it was pointed out that it was in his best interest to undertake the remedial repair work on his own, in order to avoid having the college put the repair job out to bid. This, undoubtedly, would have substantially increased the damages, a point the contractor chose not to disregard.

When the contractor did complete the repair work, and made an attempt to recover his out-of-pocket costs from the architect, a summary rejection of this claim by the architect was completely in order. Certainly had the matter proceeded to litigation, a counterclaim by the architect and structural engineer for their own out-of-pocket costs and additional work to remedy the brick distress may well have been successful. Accordingly, the ultimate decision by the contractor not to pursue any loss he sustained in repairing the project appeared to have been the wisest course of action.