Repairs on low-slope roof membrane systems

An industry-based joint effort produced a repair manual for low-slope roof membrane systems

The definition of roof slope is the angle a roof surface makes with the horizontal, expressed as a ratio of the units of vertical rise to the units of horizontal length--sometimes referred to as run. For English units of measurement with dimensions given in inches, slope may be expressed as a ratio of rise to run, such as 4:12 or as a percent.

Like any roof or roofing system, recommended maintenance is required and repairs are sometimes necessary. Therefore, to ensure the continued performance of one's roofing system, including low-slope roof membrane systems, building owners, facility and plant managers, contractors, and others now have the opportunity to refer to and use a new and comprehensive repair manual on this subject.

Organizations
In 1997 three major roofing industry organizations--the Asphalt Roofing Manufacturers Association, the National Roofing Contractors Association, and the Single Ply Roofing Institute--joined successfully in an effort to research, develop, and publish a Repair Manual for Low-Slope Membrane Roof Systems.

The manual was developed under the auspices of the three organizations' Repair Manual Task Force, as well as numerous individual companies, contractors, manufacturers, and facility managers. Special contributions came from the members of the Asphalt Roofing Manufacturers Association Built-Up Roofing Committee, the Asphalt Roofing Manufacturers Association Modified Bitumen Roofing Committee, the National Roofing Contractors Asssociation Technical Operations Committee, and the Single Ply Roofing Institute Technical Committee.

This manual details roof system inspection, maintenance, and repair. The major theme of prior publications was the inspection, maintenance, and emergency repair of low slope roof systems. As such, the previous documents were directed primarily at building owners and their maintenance staff. They also provided reference information for roofing contractors.

This new manual, while also addressing the same audience, is directed primarily at the professional roofing contractor as a guide for the identification and permanent repair of low-slope roof membranes.

This manual represents a significant effort on the part of the contributors to produce an end product that provides easy-to-use, step-by-step repair procedures, particularly for the roofing contractor. Of the many contributions made by roofing contractors and material suppliers, most notable is their ability to concur on how to best effect repairs that are doable, realistic, and not over-designed.

The format of the document highlights the individual types of membranes in four separate sections: Built-Up Roofing Membranes, Modified Bitumen Membranes, Thermoplastic Membranes, and Thermoset Membranes. Instructions for each type of repair procedure are shown on individual pages so that they can be removed from the binder, photocopied, and given to field personnel to follow. They also provide a reference guide for other users of the information. Photographs and details illustrate some of the particular repair techniques to assist the field mechanic in following the repair procedure. The repair procedures presented in the manual do not represent all of the methods available, but do represent those procedures considered to be the most reliable.

The primary purpose of maintenance and repairs for roof systems is to extend the roof's service life by eliminating leaks and foreseen problems so as to prolong and enhance the original investment made in the roof system. The underlying philosophy is that after discovering a defect that adversely affects the roof system, the root problem, and not just the symptom, should be repaired. Generally, band-aid approaches do not provide long-term benefits for either the roof or the owner and can result in more costly repairs in the future.

Depending upon the age, condition, and maintenance history of the existing roof system, the general level of repairs applicable to a specific roof membrane may be divided into three categories: spot patching, general repairs, and major repairs and maintenance.

Coatings can be beneficial in preventive maintenance programs for certain roof membranes.

Spot patching is applicable to a relatively new membrane that is in good condition, but has a few isolated sections that need to be repaired, upgraded, or reinforced to ensure long-term performance of the roof. Items that need attention may be, for example, a deficient seam, an abraded location in the field of the membrane, an open membrane base flashing, or similar.

Spot patching may also be applicable in the latter stages of a roof system's life. For example, an aged membrane that is weathered, worn, and nearing the end of its service life often can be kept functional with spot patching procedures to repair specific leaks. This extends the membrane's life a short time until funds are available or until the weather offers an appropriate window for reroofing.

General repairs
General repairs are more comprehensive than spot patching. They may involve repair of numerous deficiencies throughout the field, including various details and flashings of a roof system. The intensity of repair should be consistent with the expected useful service life of the roof. Designing or tailoring each specific repair to meet the need of each type of deficiency does this.

For example, an existing membrane may be expected to have two to four years of service life remaining, if a certain level of general repairs are performed to correct various deficiencies. With a given service life expectancy, a knowledgeable, experienced repair professional can design specific repairs or repair procedures to correct the deficiencies while accommodating the needs of that specific roof system. In other words, the professional would not design repairs to last for 10 to 15 years if the remainder of the field and flashings may only last another two to four years.

Major repairs and maintenance
Major repairs and maintenance can be viewed as a repair regimen designed in conjunction with various preventive maintenance procedures. For example, an existing smooth surfaced modified bitumen roof system may need maintenance in localized craze-crack areas, a few blisters repaired, some seams stripped-in, along with an application of the correct reflective coating to prolong the life of the membrane.

First, the membrane and flashings are repaired, then the maintenance coating(s) is applied to assist in protecting the repaired membrane from the direct effects of the weather. Coatings can be beneficial in preventive maintenance programs for certain roof membranes. For example, reflective coatings can shield the membrane from direct solar exposure, thus minimizing thermal cycling, and reducing the affects of heat aging.

The format of the document highlights the individual types of membranes in four separate sections.

When beginning a roof inspection, start at the interior of the building. Note signs of moisture infiltration such as stained ceilings or walls on the roof plan. Note also cracked, spalled, or broken masonry or concrete; water-stained, rusted steel or decayed wood members and any deteriorated roof decking. With respect to steel roof decks, certain phenolic foam insulations contribute to severe corrosion of the deck under certain conditions. Take extreme care to protect the roof membrane, the mechanic, and the building's occupants when walking on the roof deck if you suspect both this type of insulation and moisture to be within the roof assembly.

Such safety considerations are of primary importance in any maintenance and repair activity. Consider carefully the safety of the repair person, as well as the building and its occupants when planning any on-roof activity. Inspection of the roof should proceed only after identifying foreseeable safety hazards on the rooftop and taking adequate precautions. Workers who will perform the actual inspections and repairs should be trained in the procedures they will be using and in the use of mechanical, electrical, and propane-fired equipment needed to perform the work.

Thermoplastic materials require high-temperature air welders for seaming membrane material, while modified bitumen and built-up roofs may involve the use of open-flame propane torches or hot bitumens. Observe warnings and operating instructions for these tools and materials at all times. Thermosetting materials require adhesives and solvent cleaners that can harm both worker and bystander if used improperly. Read and observe the handling instructions and precautions for these products at all times. Review the appropriate Material Safety Data Sheets before starting the job and keep them on hand for easy access during and after the job.

One important factor in the success of the repair is the proper cleaning and preparation of the in-service membrane before any repair attempt. It can not be stressed strongly enough that proper adhesion of a patch cannot be achieved through a layer of accumulated dirt and grime. The specific repairs in this manual outline the proper cleaning steps needed for their success.

Ponding water is detrimental to any roof system. While most roof systems can tolerate minor ponding that dissipates within 48-hours of a rain during average drying conditions, address severe ponding as part of a maintenance and repair program. Give careful consideration to the installation of additional drains or scuppers or the installation of tapered insulation and crickets to direct the water to the drains.

The proper maintenance and repair of low-slope roof membrane systems, and the same for other types of roof systems, is a viable, vital part of any good roofing program--for the facility manager, the building owner, the plant manager, and the contractor.

Two other new Asphalt Roofing Manufacturers Association documents that will be of interest and use to plant service personnel are the Modified Bitumen Roofing Design Guide for Building Owners, and the Built-Up Roofing Design Guide for Building Owners. Both publications are intended to be a reference source for building owners that respectively address relevant aspects, issues, and concerns of modified bituminous roofing and built-up roofing systems and their associated components, substrates, and construction techniques.

The Asphalt Roofing Manufacturers Association is the national trade association representing the North American manufacturers and suppliers of bituminous-based residential and commercial fiberglass and organic asphalt shingle roof products, roll roofing, built-up roofing systems, and modified bitumen roofing systems.