CASE STUDY 1

Photo courtesy of CertainTeed

The 17 roof decks of the IERBYS

Project: Interurban Electric Railway Bridge Yard Shop (IERBYS)
Location: Oakland, California
Architect: HNTB Corporation
Roofing Contractor: Westech Roofing

The History: Sitting on the edge of the San Francisco Bay, the Interurban Electric Railway Bridge Yard Shop was built in 1938 at the eastern terminus of the San Francisco-Oakland Bay Bridge. The facility was built by Interurban Electric Railway Company as a service shop for its electric-powered cable cars and trains cars, which operated over the Bridge Railway on the lower deck of the iconic bridge.

The western span of the bridge was replaced in 2013, and the shop itself also underwent a major renovation. The $9-million Bridge Yard Seismic and Renovation Project turned the structure, listed on the National Register of Historic Places, into a dramatic exhibit and public assembly space.

The Challenge: Because the cavernous 24,000-square-foot building with a distinctive windowed sawtooth roof was considered a historic structure, the challenge was to retain the historic properties while utilizing modern, durable materials. Use of nonhistoric materials and methods could put the structure’s eligibility for listing in jeopardy. This meant that the building exterior was required to match the look of the building when it was first constructed. For the roofing system, this presented several challenges, including attachment of roof flashing to the exterior corrugated asbestos panels.

The Solution: The original roofing system was a built-up roof system applied with hot asphalt. The design and contracting teams considered installing a hot asphalt system to match. However, site-specific considerations, including limited roof access, high winds from the bay, and the excessive need to move the kettle in order to access the 17 separate roof decks, quickly eliminated this option.

The solution was to use a self-adhered three-ply system that included a mechanically attached base sheet with a film surface engineered to bond with self-adhered ply or cap sheets, a self-adhered base or interply sheet (used as an interply in this system), and a self-adhered membrane with factory-applied granule surface. The challenge of the roof flashing still remained.

On each of the 17 roof decks were two instances where the roofing was to be attached to the asbestos siding. This meant that the roofing team could not disturb the panels while installing the flashing. The solution, which met the challenges perfectly, was to use a liquid flashing.

The self-adhered bituminous system and liquid flashing met the client requirements of not jeopardizing the projects historic designation while keeping workers safe from harmful exposure to asbestos. In addition, this roofing system choice benefited the contractor by offering many safety benefits, including no torches, hot asphalt, fumes, or mess.

The new roofing system on the IERBYS not only provides the proven durability of an asphalt roof, but it also contributes to the historical integrity of the structure. The Bridge Yard Seismic and Renovation Project in Oakland won the Outstanding Historical Renovation Project Award from the San Francisco Section of the American Society of Civil Engineers.

How to Specify a Cost-Effective, Quality Low-Slope Roofing System

In order to write a specification that reflects a client’s goals for performance and cost, it is important, considering the skilled labor shortage, for architects and designers to consider both materials and labor. In other words, an architect must balance a roof system’s material costs and intended performance as specified on paper with comprehensive and current-condition labor costs that reflect actual performance once the potential for human error is introduced on the roof. The following are a few guidelines to assist in the process of specifying a cost-effective, quality roofing system while considering the skilled labor shortage.

Identify Materials Proven to Meet Performance Goals

Roof system performance goals include reliability, resistance to puncture, fire and chemicals, and ease of maintenance and repair. The lifespan of a roof depends on many factors, beginning with proper installation, but proven performance of the roofing materials must be a consideration for specification.

Single-ply TPO roofing systems have been on the market since the early 1990s. While single-ply systems have gained popularity, this product has not been time-tested in the field for as long as other roofing types. Additionally, the relatively thin, single-layer of waterproofing protection increases the system’s risk of failure from multiple potential factors over multilayer solutions.

Modified bituminous roofing systems have been in use in one form or another for more than 100 years and thus are well-known for their durability, stress resilience, and low maintenance. In addition, because of their multi-ply makeup, these systems provide better protection from damage by sharp objects than PVC or EPDM, which—although durable—are still only single-ply membranes.

Understand the Impact of Design on Product Selection and Cost

As an architect or designer, your choices regarding roof design can play an important role in determining the best product and the installed cost of your client’s roof. Across all types of roof coverings observed in the study, base flashing and equipment curbs required more labor and time to complete and can represent a significant percentage of the total project labor costs. However, some products require more labor time on roof features than others.

Overall, the labor impact of flashing details were found to be 24 percent of the total man-hours on the multilayer bituminous systems and 31 percent of the total man-hours for the single-ply coverings. It can be concluded from this data that specification of a multilayer modified bituminous roofing system can offer labor cost savings on projects with a high number of flashing details.

Understand the Local Roofing Contractor/Labor Market and Crew Factors

Understanding the local roofing contractor and labor market is becoming increasingly important for architects and designers when trying to meet client cost expectations. A little research can go a long way in determining the skillset and reliability of local contractors. Many roofing contractors are in the position of taking on more work than they can handle and then using any warm body they can find to get the work done. However, in some markets, savvy contractors are realizing the benefits of balancing a skilled, professional, and reliable crew with the amount of quality work they can complete.

Beyond the skill level of the employees, the study also found multiple other factors that impact the efficiency of a roofing crew. These include:

Climate

Climate, including both extremes of hot and cold, can have a great impact on the efficiency of a roofing crew. Cold weather creates added time and additional work for heating adhesives, relaxing rolls and to weld all types of membranes. Workers can be inhibited in movement and accuracy with heavy and cumbersome cold-weather clothing and gloves and may require longer or more frequent break periods to warm up.

Heat can also affect crew efficiency by slowing installation because of heat-related fatigue and the need to hydrate and take regular breaks to avoid heat illness.

Another consideration is geographical areas that experience frequent storms, especially summertime thunderstorm activity, which can lead to increased costs because of disrupted workflow.

As an architect or specifier, these factors are outside of your control but should be considered when specifying a roof system in line with the client’s budget. Some roofing products and application methods may be impacted greater than others by project geography.

Crew Management

A roofing crew’s efficiency is impacted by how the crew is managed. Not surprisingly, unorganized or unmanaged crews will generally increase total installed costs. Important factors to consider when understanding local roofing contractors include:

• The communication methods and style of the crew and foreman
• Whether the contractor uses specialized teams
• How the tools and materials are staged
• Whether the foreman has effectively managed crews
• How much unproductive time a crew incurs (15.6 percent according to the study)
• The effectiveness of quality control measures to catch and fix mistakes

As a specifier, and considering the current labor market, investigating roofing contractors’ abilities and track record before making final decisions may aid in minimizing issues when it comes to installation.