Proper roof specifications require a thorough description of the roof component installation process. Without identification of all component material and installation procedures, the specification is open to contractor interpretation.
Proper roof specifications require a thorough description of the roof component installation process. Without identification of all component material and installation procedures, the specification is open to contractor interpretation. It has been my experience that when the specification is open to contractor interpretation the project is less than successful.
The ideal way for the designer to provide a thorough specification is to acquire knowledge of roof materials and their application requirements. This is best accomplished from experience and proper training. ARW is committed to providing tools for success in this area. Both our technical publication and monthly webinars focus on providing continuing education in roofing and waterproofing design.
Roofs are an integral component of the building envelope and although their initial cost constitutes as little as 5 percent to 7 percent of the total building cost, maintenance costs throughout the life of the structure typically exceed 60 percent. When taking these factors into consideration, the most economical choice would be to design a high-performance roof system at the outset. However, statistics prove that this is seldom the case. Over 50 percent of all construction litigation in the United States involves roofing. This is nearly four times more than the next highly litigated component (wall systems). Furthermore, 75 percent of all new roofs have reported leaks within the first five years and 20 percent of all roof failures are due to improper design.
Improper design of roof systems can be attributed in large part to a lack of substantial knowledge of the mechanics of system components. Currently, no major architectural program in the United States addresses roof design for more than a couple of hours of study. This leaves practicing architects to expand their role as a “generalist” tying in building components. Architects are often forced to rely on manufacturers to assist in roof system design. Problems in this relationship arise because manufacturers have limited analytical expertise in other manufacturers' materials and systems, and their vested interests in selling their own products, preclude them from being impartial.
In some cases, roofing contractors act as specifiers - often using systems for which they are the most familiar and of which they can make the biggest profit. Contractors lack knowledge, expertise, and resources to objectively evaluate the problems and suitability of materials that will perform best under field conditions.
A disturbing practice often utilized by roof designers is the insertion of manufacturers’ technical requirements as specifications. These documents - which are sometimes represented as specifications to designers by overzealous manufacturers’ representatives - are in fact only guidelines established by manufacturers to set tolerances for the application of their materials. Manufacturers state in these documents that they are not intended for use as design documents. The fine print attempts to absolve them of all liability in design issues. The guidelines and details provided by manufacturers often change. In fact, at least one manufacturer is considering discontinuing the distribution of annual technical publications due to the rapid detail changes employed throughout the year.
Reliance on manufacturers’ warranties as design criteria provides another set of problems. As I speak to architectural groups and designers throughout the country I have found there are common misconceptions that designers place on the value of these warranties. The concept of the warranties in the roofing industry initiated as a marketing tool for manufacturers who were placing new and unproven products on the market. Warranties limit the manufacturers’ liabilities and most warranties provide no more retribution than the coverage of material costs for roof leaks that are reported within 24 hours of occurrence. The limitations often exceed the coverage. The roof designer should read the fine print of all warranties and decide what type of warranty is best suited for the project. No warranties include coverage for design issues; this falls back to issue of manufacturers not taking responsibility for design.