Perspectives
A Quarterly Information Source from Benchmark, Inc.
Volume 37 September 1999

Low Maintenance Roofing Systems

by Tom Irvine, RRC

As roof consultants, we are committed to controlling our clients' roofing costs at every opportunity. One way we carry out this mission is by closely examining future roof maintenance considerations when recommending and designing roofing solutions.

Generally, the less dependent a roof system is on maintenance, the longer the roof will perform without requiring repairs or replacement. By prolonging the roof's service life and minimizing the need for repairs, the cost per year of roof ownership can be substantially reduced. In the absence of regular maintenance, this design philosophy will also postpone interior leak development, as well as moisture infiltration into the roof system.

• building usage
• types of rooftop equipment and associated equipment maintenance procedures
• presence of manufacturing by-products/debris
• anticipated levels of foot traffic
• presence of non-roof related construction traffic on the roof
• planned future rooftop equipment modifications
• type and condition of flashing substrates, adjacent walls, and roof penetrations
• proximity of roof to overhanging trees, salt water, pollutants, etc.
• roof drainage characteristics
• probability of vandalism
• other site-specific factors affecting the roof

Low Rise Mixed Use Plaza
The client owned a five building complex consisting of leased offices, restaurants and shops. Tenant turnover was fairly high, with interior renovations occurring on a regular basis. As such, roof penetrations were often added and removed by a wide variety of subcontractors. All buildings had gravel surfaced built-up roof systems. While these systems do have the advantage of being traffic resistant, the gravel makes quality tie-ins difficult to construct at new penetration flashings and repair areas. As a result, the property manager was constantly chasing roof leaks, most of which resulted from tie-in problems. In fact, the facility's roof repair contractor had a contractual obligation to dispatch a repair crew to the property whenever it rained.

Pulp and Paper Mill
This client owned an older pulp and paper mill in the southern United States. In response to catastrophic roof leakage and an overwhelming backlog of roof replacement work, the owner elected to install single-ply EPDM roof systems due to the low cost and volume of work that could be performed. This solution was in essence designed for high maintenance. The high frequency of adjacent construction work, debris/cleaning, roof traffic, and incompatible chemical discharge, lead to rapid membrane puncturing and saturation of the roof insulation. To avoid repeating roof replacements within 4-8 year timeframes, extensive repair and maintenance work had to be completed on a regular basis.

Roof Related Sheet Metal
Sheet metal components provide the first line of defense against water intrusion at roof perimeters and penetrations. When leakage first occurs in a roof system, it commonly originates in either of these two locations. Investing in a "belts and suspenders" approach typically pays off, if the objective is long-term ownership.

Parapet walls and expansion joints can be wrapped with a single-ply membrane prior to installing metal coping caps and expansion joint covers. If joints in the metal open up over time, the building and roof system will be isolated from water entry. Without the membrane underlayment, this water could run behind the flashings and into the building.

Perimeter counterflashings are typically either surface-mounted or function as part of a wall system. Surface mounted counterflashings rely on a bead of caulking to keep the water out. Integral wall counterflashings are typically cast into a masonry wall, or secured within a metal panel or stucco wall system. Integral wall flashings are also added after the fact by saw cutting a reglet joint and using this groove to secure and seal the top of the counterflashing.

As surface mounted counterflashings rely on sealant maintenance to protect against leakage, we opt for the integral style whenever possible. The integral style relies on watershedding ability and placement of the top edge of the metal within the wall assembly, which are more reliable in the absence of roof maintenance.

Types of metal and fasteners specified also affect the longevity of roof terminations. Proper fastener types with corrosion resistant coatings will slow fastener corrosion compared to that of commodity grade zinc coated fasteners. Metal types and finishes also vary widely. A maintenance-free factory applied coating such as Kynar 500/Hylar 5000, or stainless steel will generally prevent corrosion and finish deterioration, compared to galvanized steel.

Flashing Terminations
The use of pitch pans should be discouraged, especially if other flashing options are available. Pitch pans are easy to install in the field, but need to be filled and repaired frequently. If this maintenance is not performed judiciously, water infiltration is highly likely. If pitch pans must be used, proper surface preparation, use of premium sealant material, and installation of a metal cover should be required to reduce maintenance concerns.

Where flashings are terminated with sheet metal, especially surface mounted counterflashings, a secondary line of defense is worthy of consideration. This ensures that water will not leak into the flashings should it get behind the metal. With modified bitumen flashings, this is typically achieved by top nailing the flashings and sealing the upper edges with roof cement and fabric. With single-ply flashings, this may be performed by installing water cutoff sealant behind the top of the flashing and installing a termination bar to attach the flashing and compress the sealant. This bar is then typically covered by the sheet metal counterflashing

Integral style counterflashing detail.

Conclusion
Many other opportunities exist to implement low maintenance roof system and detail design that are beyond the limits of this article. The point to keep in mind is that maintenance requirements and roof ownership costs can be reduced if key decisions are well thought out prior to installation of a roof system.

Several of Benchmark's clients have requested assistance in developing a standard operating procedure (SOP) to govern roof-related activities. These standards are typically implemented and enforced by facility management and maintenance personnel to minimize roof ownership costs, maintain good roof integrity, prolong roof service life, and maintain roof warranties. These clients have made it mandatory for all contractors, inhouse maintenance employees, and engineering personnel to follow SOP requirements.

Watch for a future article in Perspectives that provides a detailed look at SOPs, and the associated benefits.