DPR Uncovers Roof Issue, Devises Solution for Kaiser Permanente Laboratory Renovation

While working on complex, large-scale projects, the question is rarely whether unexpected issues will be encountered along the way; it’s usually how well you’ll handle them when you do. Though recent developments in technology, such as 4D CAD software, minimize surprises, DPR like all construction companies frequently finds itself uncovering new challenges as projects progress.

Recently, a 19,000-sq.-ft. tenant improvement project in Berkeley, CA, for Kaiser Permanente led a team to one of those unexpected discoveries. As the team started renovating the laboratory to make it suitable for cytology, gynecological and non-gynecological prep, flow cytometry, grossing, and research & development departments, deficiencies in the structure’s foam roof were found. The project team soon determined that on top of the expected scope, which included completely removing all the existing walls, ceilings and flooring from the building and then building everything back, they would need to remove and replace the foam that coated the metal roof of the 20-year-old, steel-framed, metal-sided facility.

Structural constraints required a lightweight roof, while California’s Title 24, which regulates energy efficiency standards for residential and nonresidential buildings, specified a R19 insulation value. After considering the options, including replacing the entire roof—metal panels included—foam was selected for the building.

“DPR hasn’t done many foam roofs,” said Ray Trebino, DPR project manager. “With a 20-year warranty, minimal impact on the existing facility and virtually no maintenance issues, foam roofing emerged as the best solution in this case.”

Crucial to the success of the new roof installation was total removal of the old foam and correct preparation of the metal to assure proper adhesion between the roofing surface and the primer. Once the existing foam was removed, DPR discovered that the coating on the metal roof was more resistant than previously thought.

To completely remove the foam and assure bonding of the new product’s primer, the team spent an entire weekend sandblasting the laboratory’s roof, taking extra care as they were just a few feet away from other occupied buildings. Once the residual foam was removed, the roof was primed and prepared for the new foam. To ensure it performed properly, and that its warranty would be honored, DPR carefully coordinated the application process.

Randy Eissner, DPR superintendent explained, “To guarantee performance with this product, we had to precisely follow the product’s specifications, even down to monitoring the roof surface’s temperature to make sure it was 60 degrees and rising before application. We also had to be careful to monitor moisture and humidity levels because the foam is very sensitive to moisture and will not adhere properly in its presence. This was particularly tricky because we were facing the roof project during November of last year, which was one of the wettest months in history.”

In addition to using blowers and brooms to clear any dew off the roof, the crew adjusted the schedule and worked overtime during the windows of dryness to pull in the schedule. The team also had to take into account the possible effects of another element—wind—which could cause overspray and inadvertently coat adjacent buildings or vehicles. To prevent this, a mobile enclosure was utilized in congested areas.

Once applied, the roof requires little maintenance, but heavy foot traffic can break down the foam. To preserve it, DPR installed walk pads around the mechanical maintenance areas, where the load will be heaviest. Because the acrylic finish coats are very slippery, a ceramic granule broadcast was used in the final coat to prevent accidents.

“This was an unusual project for DPR, since foam roofs are typically used on standard, no-frills ‘big-box’ type structures rather than the technically complex facilities that we generally build. However, through the process, we learned that foam roofs can be a good alternative for buildings with weight and insulation restrictions,” said Trebino.