D. C. Taylor Co. Reroofs Historic San Francisco Armory Barrel Roof
Used most recently as the headquarters for Armory Studios, former owner and entrepreneur Peter Acworth wanted to convert the 1914 San Francisco Armory’s 40,000-square-foot drill court into an entertainment venue for concerts and events.
In the 1920s, the 4,000-person concert hall of the brick Moorish Revival castle hosted prizefight boxing matches, earning it the title of “Madison Square Garden of the West.” It remains one of San Francisco’s largest unsupported enclosed spaces today. The building was placed on the National Register of Historic Places in 1978.
With the installation of a high-end wood floor in the drill court, it was imperative to keep the building watertight. General Contractor Yerba Buena Builders, Inc. subcontracted D. C. Taylor Co. to perform the roof replacement in spring 2017, having successfully worked together on other projects in the past and because the roofing contractor had previously performed roof maintenance at the Armory.
Scope of Work
D. C. Taylor Co. coordinated the removal of the existing foam and asbestos-containing built-up roof systems down to the wood deck with a tear-off subcontractor licensed to perform the work. The old 48,200-square-foot roof system was estimated to be approximately 40 years old.
Following the removal of the old roof, a 10-man crew cleaned the existing drains and prepared the wood deck for the new roof system. The new insulation system consisted of one layer of 2.5” polyisocyanurate insulation and a layer of ¼” DensDeck coverboard, mechanically fastened to the deck. The new membrane was Sarnafil 60-mil, S327 PVC, mechanically fastened to the deck. The D. C. Taylor Co. crew installed the G459 flashing system at perimeters and projections per manufacturer’s specifications and installed Sarnatred walkway at the designated traffic areas.
Challenge #1: Roof Access
A stair tower was erected to access the roof. Due to interior activities, it wasn’t practical to walk through the building and access the roof, although a door was available for a secondary means of egress. Access to the stair tower had to be secured and closely monitored to keep non-project individuals from trying to enter the work area. The crew quickly became efficient with their trips to and from the roof to avoid the six-story climb. The view from the top was pretty special though.
Challenge #2: Downtown building
Downtown San Francisco is very congested; it’s a tough environment to perform construction projects. There’s extremely limited parking and nowhere to stage materials. Crews had to contend with ongoing vehicle traffic while trying to move materials to and from the loading area, as well as a lot of foot traffic and a transient population creating the need to lock tools, port-o-johns, etc. to avoid theft and misuse of company/rented equipment.
The general contractor had to erect scaffold and close the sidewalk on one whole city block. Originally project planning called for full crane mobilization but D. C. Taylor Co. worked with Yerba Buena Builders, Inc. to install a second scaffold platform and debris chutes to avoid needing the crane and full street closures.
Challenge #3: Limited material staging
Materials were kept in the Armory’s basement, which originally contained storerooms for field wagons. What the crew needed was pulled out at the beginning of every day. D. C. Taylor Co. used two
powered smith hoists. One was placed on top of the stair tower, and then another on the flat part of the barrel roof to get materials loaded first from the ground to the roof’s edge and then to the center of the barrel roof. Material handling and debris handling was extremely challenging and labor intensive.
Challenge #4: Steep barrel roof
D. C. Taylor Co. crews had to execute the project while repelling. This required extreme safety precautions and vigilance. Several members of the 10-man crew had experience roofing Northern Michigan University’s Superior Dome and were familiar with the double tie-off fall protection that was necessary.
Crew members wore body positioning harnesses, where there was one single point of tie-off with a self-retracting lifeline (SRL) that would stop them if they fell and a second body positioning rope that kept them in position to complete their tasks. Workers were stationed at various points on the barrel roof forming an assembly line to pass the bags of debris up to the roof staging area and the materials down to people at the base of the barrel for installation. Tool lanyards were used to secure hand and power tools and electric winches were set-up if items were too heavy to safely pass by hand.
Except for the 3,000-square-foot flat area on top of the barrel, 100-percent tie-off was required. The project was completed over three months with no injuries.