Préserver l’histoire : L’Irvine Ranch Historic Park refait sa toiture
by Alex Pecora, director of residential product marketing, CertainTeed Roofing
(this article first appeared in the Sep/Oct 2016 issue of Western Roofing Magazine, and has been reused with permission)
Remodeling or reroofing government-owned historic structures requires a delicate balance of preservation and achieving compliance with modern day building standards. Though preserving the architectural style and appearance of the original structure is crucial, it is equally important for such projects to utilize building materials and design strategies that will bring the structure up to today’s building and fire codes. The project team handling the recent restoration of seven buildings on the grounds of the Irvine Ranch Historic Park in Irvine, California, was faced with this exact challenge.
The buildings, most exceeding 100 years of age, were located on 16,5 acres of original land from the Irvine Ranch, which was founded in 1864 and grew to be one of California’s most productive large-scale agricultural enterprises. The Irvine Company deeded the land to Orange County, California’s park department, OC Parks, in 1996 to be redeveloped as a park. In 2008, OC Parks moved its headquarters to the park. The department soon began making plans for the $5,8 million renovation of seven onsite buildings, including The Irvine Company’s original agricultural headquarters, an early office building, a mess hall, a ranch hand bathhouse, and three homes built for ranch foremen over the years. The buildings would provide much needed office space for OC Parks after completion.
Construction work began in 2013, with Thirtieth Street Architects, Inc., of Newport Beach, California, and general contractor Spectra Company, of Pomona, California, at the helm. The project involved reinforcing their frames, retrofitting them to withstand earthquakes, as well as the installation of wheelchair ramps, new electrical, plumbing and HVAC systems, and the restoration of windows and siding. And, with their advanced age, five of the buildings needed new roofs.
The project’s architectural firm studied each building to determine which roofing materials were used originally and which would be most feasible as the replacement roof material. One of the materials was not a good match with contemporary codes.
“For this project, the roofs were required by code to have a Class A fire rating, and the mess hall and early office building originally had wood shingles as their roofing material,” said Carrie Wilde, LEED AP, architect with Thirtieth Street Architects. “If we wanted to achieve the Class A fire rating, installing new wood shingles on these buildings, unfortunately, would not be possible. Thus, we began looking for an asphalt shingle that would display shadow lines and other features of the intended historical look while meeting today’s code requirements.”
This selection was not a stretch for the three foreman houses, which the architects believed had asphalt shingle roofs from the beginning. The bathhouse had a tin roof, which was not replaced. The foreman houses also stood out because they displayed more exterior color than the mess hall and office building. Therefore, finding historically appropriate shingle color blends that would complement the buildings also became a priority, Wilde said.
In the end, the architects specified CertainTeed® Landmark® designer shingles, which replicate the look of wood shakes, while offering the high fire and wind resistance of asphalt shingles. Working together with OC Parks, they then chose the best shingle color blends for the buildings.
Spectra Company, Pomona, California, subcontracted the reroof portion of the project to Pacific Single Ply Roofing, Inc., of La Habra Heights, California, a contractor whom they had worked with successfully on previous projects. Roof work began in mid-2014, with the general contractor and roofing contractor working closely together. Spectra Company’s crews removed existing roofing materials and reframed the buildings, making adjustments to help the roofs comply with building codes and roofing product manufacturer warranty guidelines. The existing roofs were in poor shape. The original wood shingles had been removed at some point, and the original sheathing was replaced with plywood and followed by asphalt shingles. The crew removed all of these materials. Spectra Company’s crew then replaced the rafters with more historically accurate, code-compliant rafters and new sheathing.
Due to sometimes ill-informed additions made to the buildings over the years, the crew ran into several irregularities, such as low valleys and low-slope portions butting up against steep slope portions. “We got into so many problems with the original roofs,” said Troy Parry, project manager for Spectra Company. “Every time we got started reframing a building, we would find something and have to correct it. We didn’t make any changes to the architectural style, just modifications to make a roof everybody could stand behind.”
“They would get a portion of a building done and move to the next one, so we could get back up there and keep everything as watertight as possible,” said Al Montoya, owner of Pacific Single Ply. “That’s very important with the old buildings because they can grow mold really quickly.”
On each building, Pacific Single Ply’s five-person crew nailed CertainTeed WinterGuard™ waterproofing underlayment to each wood roof deck and SwiftStart® starter shingles along the eaves. They then installed the Landmark designer shingles and Shadow Ridge® ridge cap shingles and finished with new flashing. The pitches of the roofs typically ranged from 6/12 to 7/12 and the height was often about 15 ft. off the ground, so the roofing crew used fall protection equipment to stay tied off and built small platforms on the roofs to keep roofing materials from sliding off.
Pacific Single Ply also encountered two low-slope roof portions and one irregular chimney flashing that required SBS modified bitumen roofing. For this, they recommended and ultimately installed CertainTeed’s Flintlastic® SA three-ply self-adhered low-slope roof system. This involved nailing down a Flintlastic SA Nailbase base sheet, followed by peel-and-stick applications of the Flintlastic SA Midply and Flintlastic SA Cap Sheet. All roofing materials for the project were supplied by Structural Materials Co., of Commerce, California.
“This was the first time we tried a self-adhering roof system, and I was pleasantly surprised by how well it worked,” Montoya said. “It was easy to install, stayed down, and the manufacturer rep from CertainTeed was very helpful.”
All in all, Pacific Single Ply installed 160 squares of roofing over nine months. The project was finished by the summer of 2015, and OC Parks occupied the buildings soon after. “The end result was very positive,” Parry said. “The project came out great, and the shingles looked wonderful. Pacific Single Ply did six roofs for us, and not one of them leaked.”