Barrel Roofing the Boston Convention Center
I recently had the opportunity to witness aerial-roll-forming panel fabrication in progress at the Boston Convention Center. My host was Nathan Daniel, corporate safety director of the Hartford Roofing/Titan Roofing joint venture, the roofing contractor on the project. When I arrived at the site, the BEMO Mobile Panel Forming Mill was already hoisted and installed at the roof edge and running flawlessly. It is engineered to form straight, curved or tapered panels of most common roof metals to virtually any length desired.
The whole process was technologically sound, deceptively simple and obviously profitable. The sheet metal crew was well trained and already had several days of experience in the panelizing process. The winds off Boston Harbor were calm and dry and the temperature for late November was bearable, in the low 40s.
To date, the Boston Convention Center is an $850 million project located near the perimeter of South Boston’s Big Dig, just five minutes from Logan International Airport. It will contain a total of 1.7 million square feet of commercial exhibition, meeting and administrative spaces. It is just part of a larger $944 million private- and state-funded development package that may or may not receive adequate investor support. The “big picture” is to build and renovate hotel, meeting and exhibit spaces, shops and parking facilities around the BCC and throughout Massachusetts. But with the City of Boston and the state legislature already contributing over $150 million to the project and the Big Dig
significantly overrunning it’s budget at $14 billion, the state’s coffers, as well as its constituency, are strained to the breaking point .
The Massachusetts Convention Center Authority called for a halt to all design work in January 2001 when the structural steel bid came in more than 50 percent over budget. Originally quoted at $650 million, many design revisions and deletions were implemented to reduce final costs, including a 100,000-square-foot reduction in the exhibition space. The MCCA has suffered much media criticism for its insufficient and/or inadequate management practices. The capital costs (still $100 million over budget), schedule (completion moved from 2003 to 2004), site location (over 100 miles of deep, driven piles to bedrock) and site conditions (widespread hazardous soil contamination) required all of the prime and subcontractors bidding the work to pull back and critically revise their material, labor and equipment quotes. The sounds of No. 3 pencils being sharpened reached far into the night.
The BidThe roof bids were particularly sensitive not only to the reduced budget, but also to the critical-path schedule that marked the waterproofing/roofing phase in the late autumn/early winter months. In New England along the coast, that can be challenging, to say the least. The MCAA subsequently issued change orders to lower the cost of the membrane, which included changing the originally specified metal flat roofing to membrane.
The BCC’s flat roofs — located over the offices, meeting rooms and mechanical areas on the east/west sides — constitute 476,130 square feet and were changed to Firestone TPO roofing mechanically attached to metal deck and fully adhered at the concrete deck locations. It was obvious that the roofer with the best price on the barrel roof over the main exhibit hall — who could also convince the battle-scarred MCAA and the owner’s rep that the project was not going to run over budget or beyond completion date — would most likely be awarded the bid.
The main exhibit hall roof is a segmented barrel with a north/south center ridgeline and a variable radius of 558 feet (15 percent tangent) on the north end to 971 feet (9 percent tangent) on the south. The architect’s original specification of 0.040-mil aluminum standing-seam roof panel remained unchanged. The recommended suppliers included Merchant & Evans Inc. (Zip Rib), Overly Manufacturing Co. (Overly Metal Batten) or Bemo-USA (BEMO 400 Panel).
Material- and labor-cost savings were to be the name of the game. The circumference of the irregular chord of the barrel is approximately 300 linear feet, while the north/south eaves are more than 1,500 feet long. With a total of 457,033 square feet of roof area, and a center ridge to eave elevation differential of over 37 feet, running continuous, seamless panels was the best design to prevent the risk of rain penetration and uplift. There is also a very complicated 318 stainless steel parapet-gutter-leader system and a bullnose coping, which were integral to the ironworker’s bolt-on eave and soffit frames and will eventually prove labor-intensive under the best of conditions.
On a professional basis, the joint venture roofing contractor was understandably reluctant to disclose any final per-square-foot installed rates or work/time studies. Depending on a variety of site conditions and process details, I would speculate that, all other factors being equal, BEMO’s aerial-panel-forming process could provide 10 percent to as much as 20 percent savings on roof labor alone compared to conventional standing-seam panel installations. Additional savings could be estimated by minimizing crane time on the project, reduced lay-down area required for on-grade panel storage, fewer ground and roof crews, and less waste removal and disposal fees from shipping dunnage and panel crating.
It is obvious that the joint venture roofing crews were becoming well versed in the panel handling and delivery techniques required for aerial panel forming. Any crew with more than one BEMO job under its belt could certainly prove increasingly profitable.
The AwardBy early April 2001, Clark/Huber, Hunt & Nichols/Barry awarded the roof bid to the joint venture of the Hartford Roofing Co. Inc. (HRC) and Titan Roofing Inc. (TRI). With corporate offices in Glatonbury, Conn., HRC has satellite offices in Stoughton, Mass., Providence, R.I., and West Haven, Conn. A sister office has been established in Orlando, Fla., as Hartford South Inc. The company has more than 75 years of commercial and industrial experience and employs over 500 roofers and sheet metal workers in New England. HRC is the second largest privately owned commercial roofing company in the United States.
Under the safety direction of Nathan Daniel, the site-specific job-hazard analysis and safety and health program for this project was designed and implemented and then submitted to the general contractor for approval. HRC is providing the overall project site superintendent, site safety and health auditing as well as a competent person foreman on the barrel roof.
TRI, established in 1978, is one of the larger roofing contractors in the Northeast. As such, it was well-positioned to form a joint venture with HRC. Its engineering capabilities enable the company to easily coordinate with other firms and maintain an upgraded work site regardless of structural conditions.
The HRC/TRI joint venture provided up to 45 roofers and sheet metal workers to install the substrate above the steel N-deck, including the vapor barrier, structural insulation panels, and snow-and-ice shielding membrane.
The sheet metal workers next apply all the aluminum panels, clips, flashing, coping, gutters, bullnose eave trim, and miscellaneous roof accessories (snow guards, personal fall arrest anchors, roof vents, etc.). While both HRC and TRI are of sufficient size to complete comparable projects almost anywhere in the world, this was a substantial job right in their own back yard. The management and infrastructure of any project is much simpler to handle when the distances, communications and responses are not limited by great mobilization distances, unfamiliar labor sources and first-time subcontractors. Both firms already have a close New England partnership — they are members in and leaders of the Northeast Roofing Contractors Association.
In addition to the design and development of the Roofing Industry/OSHA 12-hour Outreach Training Program, a “Zero Accident” safety mission and a budget-driven schedule became crucial to the project’s substantial completion.
Shaughnessy Crane Service was subcontracted to provide the labor and equipment to supply and suspend its panel fabricator above the roof. The late 2002 season roof start date and late summer 2003 completion date necessitated that the vendor could provide a flexible fabrication and supply schedule. This was obviously weather-dependent upon the onset and depth of winter 2002-03. BEMO-USA submitted its lump-sum quote based upon an agreed number of production days with a broad range of options to demobilize and remobilize as required. They also guaranteed a continuity of quality control, with the same two-man operation team throughout the project.
According to estimators for the joint venture, BEMO’s immediate response to their design RFIs, comprehensive on-site consultation, technical design assistance, estimating comparisons and take-off capabilities quickly set them apart from their competitors. As everyone knows, timely response and direct face-to-face assistance from vendors on a large pre-bid project can often make the difference when product and service is finally selected. Before long, it was apparent that BEMO-USA was up to the physical, as well as the fiscal, challenges of the BCC. They were awarded the metal panel supply contract by the HRC/TRI joint venture by the end of April 2002.
The BEMO SubroofThe barrel subroof system began in mid August 2002, soon after the ironworkers had “puddle welded” almost 10 acres of steel N-Deck over the 300-foot-long arch trusses. The product from the subdeck to the finish panels was all produced and provided by BEMO-USA. The roofers began by installing a continuous vapor barrier (Sarnavap® 10-mil polyethylene VB) over the conditioned areas below. Next they installed over 1,400 staggered 4-foot-by-8-foot-by-33/4-inch composite insulation panels. Each panel consisted of 3 5/16-inch polyisocyanurate insulation laminated to a 7/16-inch OSB panel and weighed approximately 48 pounds. These were fastened down to the galvanized steel N-deck using Olympic self-drilling/tapping screws with 3-inch plastic washers. The quantity depended on engineered uplift exposure.
This panel installation was followed up with BEMO’s 60-mil adhesive, self-sealing rubberized, fiber-reinforced “snow-and-ice” underlayment (GAF Metalmate HT). This product was selected for its ability to remain exposed, undamaged to the elements for longer periods of time before the finish roof is applied. It is also resistant to the higher temperatures generated in the warm months underneath the metal panels. Since the prevailing east winds can average 30 mph with gusts to 40 and above, the roofer’s material handling procedures had to be monitored carefully to prevent any loss or injuries.
There were two expansion joints dividing the barrel into three sections approximately 350 to 400 feet long, with a lower and narrower 400-foot barrel projecting over the Summer St. entrance. Each expansion joint ran 300 feet over the barrel and was sealed with a rubber membrane and covered with a hazard yellow metal skin and 3/4-inch CDX plywood bridges for material, labor and equipment crossing.
The BEMO Roll-formed Panel SystemThis is the first time HRC/TRI had worked with the BEMO-USA roll-formed panel system. BEMO is an international metal roofing firm founded 30 years ago in Stuttgart, Germany, and currently operating in 11 countries. The company recently completed the largest stainless steel roof in the United States for a 1-mile-long hanger at the Detroit Metropolitan Airport. The U.S. operations were established in 1996 and now operate three mobile rollers with an average output of several million square feet per year.
Within the first week, approximately half of the project’s BEMO halter clips (more than 50,000) were installed over the snow-and-ice shield along lines 15 3/4 inches apart parallel to each edge of the pans at approx. 40 inches on center. These were drill/driver fastened with 5-inch stainless-steel self-tapping fasteners through the composite insulation boards and into the N-deck.
The BEMO Mobile Panel Former, which was constructed inside of a steel-ribbed shipping container, may be easily trucked from site to site or delivered overseas. This particular 20-ton unit was powered by a ground-based Denyo 45-kilowatt diesel generator, which provides a 440-volt, three-phase power supply to the suspended box through an insulated umbilicus.
The ground man gave me a tour of the unit while stationed on the ground to be reloaded with another 1,500- to 2,000-pound coil of 0.040 aluminum stock. The coil is placed by a Lull all-terrain industrial lift truck onto a four-way hydraulic clipper loading platform, which takes the coil through a large access door in the side of the container and places it on the de-coiler spindle at the rear of the panel former. The field roll former can also be ground-installed on a hydraulically inclined flat bed with scissor lifts, scaffolding and conveyor sections to form and deliver metal panels to a lower roof edge.
All air-driven operations such as the decoiler, brake and former controls are simply pressurized by a small electric air compressor partially hidden by the maze of wires, pipes and panels on the opposite side of the panelizer rollers and formers. The ground man enters the unit on the ground to load the coil and feed the stock into the former and perform any maintenance, adjustment or repairs necessary. He also controls the hoist with the aid of a tagline until the container is secured to the roof’s edge or grounded at the landing site (controlled access zone). There are 12 sets of adjustable 12-inch-diameter stainless-steel forming dies over a roller bed, through which the coil stock runs and is finally formed.
Each 400-millimeter-wide pane has a male and female edge, including a 2 9/16-inch-high standing-seam form, which interlocks during installation of the halter clips on the roof deck. At the end of the forming bed is the automatic pneumatic shear. The computerized telemetric controls have been preprogrammed for each panel length, as the radius and panel lengths change at various points along the roof’s length. Individual panels are produced in a reverse order from a predetermined starting point on the roof and the stockpiling of these panels proceeds back to the fabrication point at the crane staging area.
A typical panel leaves the BEMO roll former through a small opening at the discharge end of the container at 125 to 150 linear feet per minute. The mill produced a typical panel in less than two minutes. The panel stock is finished with a PPG Duranar XLE® silver metallic coating with a 1.35-mil poly clear coat. The sealant glue applicator — located just beyond the shear — micro-sprays a 300-degree adhesive to the underside of the female (upper) locking edge. Drying to tack within the first 10 feet of horizontal run, it is meant to adhere the male edge of the adjoining panel during installation and crimping to provide a waterproof seal to the joint.
The BEMO operator on the roof is equipped with a full body personal fall arrest system and shock-absorbing lanyard suitably anchored. The operator remains 100-percent tied off during the positioning of the unit at the roof’s eave beyond the gutter parapet, while retrieving the control pendant from the unit, which simply controls the on/off functions.
Begun in early November, the four-week first phase of the barrel roof job projected that approximately half (45 percent) of the BEMO 400 panels (580 panels or 228 squares) could be installed if the late November weather cooperated. These phase-one panels were fabricated, stockpiled and secured in seven-unit piles up to the mid length of the roof barrel in five days, thereupon releasing the crane, operator and oiler until phase two. The individual 300-linear-foot panels were lifted off 15 4-foot-by-2-foot roller beds, attached to 32-inch saw horses, and set on 15 four-wheel heavy-duty roof carts padded with two blocks of 4-inch polyisocyanurate foam. A total of seven panels were loaded and tied down with nylon straps before the crew began moving the carts by pulling, steering and pushing.
At the delivery point the carts are wheel-chocked and the roofers cross over the panels and unload them, one at a time, onto a stack blocked up between roof halter clips approximately 3 feet away from the cart line. This allows for the future installation of the panels without repetitive handling. The longest delivery was over 750 feet and took the crew less than 30 minutes to unload and return to the staging area. During this time, the BEMO crew deployed the mill to the ground, reloaded a new coil of panel stock and hoisted the container back into position on the roof’s edge.
Once an adjoining panel is placed on its mate, a manual hand crimper is used to hold and stabilize the new panel at each halter clip. Then a BEMO mechanical seaming tool is attached to the rib to be seam locked. This is a variable-speed, 110-volt electric, UL-approved device that is locked down on the panel seam before operation. It is powered by 10-gauge GFCI-protected lead chords less than 100 feet from the portable Honda generator. While the front nylon wheels guide the unit, the rear steel wheels form the material into a locked position around the halter clips and a continuous waterproof, structural seal. A deseaming tool must be used to unlock seams for future panel removal or replacement.
Once the seaming tool is started, the nylon forming wheels send it up over the barrel radius to another worker on the other side who shuts it down, locates the unit on the next seam and sends it back again. A factory-adjusted, lubricated seamer with seams free from debris and obstructions can cleanly close 300 linear feet of standing seam in a few minutes. The properly applied and finished panel roof is warranted by BEMO for a 20-year finish and — when all flashing and gutter seams are tig/mig solid welded — for 30-year watertight integrity.
BEMO’s mobile panel former, seamer and panel material are well designed to reduce crane time, material handling and potential fall hazards while increasing profit and productivity respectively. Once the spring weather arrives, phase two (four to six weeks) will require remobilizing the crane to the north end of the roof where the balance of the roof panels will be formed, located and installed from the halfway point back toward the north end of the barrel. The barrel roof job is scheduled to be completed by July 2003.
The Lift PlanThe Shaughnessey’s operating engineer and competent person was Al
Moulton, who has more than 29 years of crane experience. Earlier in the project, the joint venture safety director renegotiated the crane pad location with Shaughnessey and the general contractor. This location was inside a concrete access ramp under construction, which would have restricted the crane to a hazardous “high-stick” position and required the crane to rotate on the truck to “blind” set the panel former box on the opposite side of the ramp. While typically this lift can be done by a 125-ton crane, the crane for this operation was a 360-ton hydraulic Liebherr, Model 1300/1-36e.
To facilitate the lift and minimize hazardous exposure, it was agreed that the crane was best located on the opposite side of the access ramp, and the lift involved only boom in/out and load up/down without the risk of rotation. The crane site soils were field tested by Briggs Engineering using certified radiological compaction testing equipment. The soil’s density and compressive strength were calculated. However, as the hydraulic soil conditions were saturated, the competent-person operator called for four oversized pads for his four outriggers, including 8-foot-by-8-foot solid oak beam “rafts” covered with curbed, 1-inch steel plates.
The “non-critical” lift plan was developed by the HRC/TRI joint venture and Shaughnessey Crane and submitted to Carl Ricks, safety manager for Clark/Huber, Hunt & Nichols for approval. The Liebherr has a maximum 151 feet of boom and operates in all lifts at a stationary vertical boom angle of 60.1 degrees (at the roof) and a cab rotation 76 degrees off center truck. It utilized approximately 78 feet of boom at the final lift position and 66 feet with the box landed. The BEMO panel former and steel container grosses about 41,500 pounds fully loaded with a 1,500-to 2,000-pound coil of aluminum.
According to the crane lift-capacity charts, with only partial counterweights, the maximum-rated load of the lift was 76,000 pounds. The lowering/loading/inspecting/lifting phase of the pick takes 20 to 30 minutes. When in the raised position, the panel former bears its discharge end on a reinforced landing deck at the eave. The load line was then reversed until the four-bridle wire-rope sling inclined the box back from the roof edge at approximately 3 to 5 percent from horizontal. This negative pitch to the mill closely matches the variable tangent of the roof for ease of placement.
The Site Safety ProgramThe joint venture’s safety department collaborated early in the project to analyze the roofing procedures for potential hazards. Their tool of choice was the job hazard analysis system. I have written extensively about the JHA (also called a job safety analysis) over the years, but before encountering Hartford roofing a year ago, I have seldom audited any construction firm where this procedure formed the backbone of the construction management plan as well as the owner’s mission statement.
JHAs for the BCC project were produced and analyzed during the months prior to prebid and continue through this date of publication and beyond. In a JHA, the field supervisors itemize the phases in the bid and break them down into their sequential steps. They then analyze the individual steps for existing and potential hazards. JHAs enable the employees and the safety committee to institute engineering hazard controls, safe work practices and suitable personal protective equipment and training to eliminate or reduce most hazards. OSHA naturally prefers that the employees have input into their own safety and health, and there can’t be hazard awareness without hazard communication.
After review, the joint venture submitted its final site-safety plan and hazard communication program to Joseph Salerno (project manager) and Carl Ricks (safety director) for their review and subsequent approval. Those unsafe acts or conditions that could not be totally eliminated (such as windy conditions) were best approached by constantly training higher awareness levels in the roofers and thereby reducing them to lower hazard exposure levels. Then all of the employees on the site were trained on the emergency action plan for the project. Safe roof evacuation procedures were modified as the production of the roof proceeded. An emergency rescue plan to remove an immobilized accident victim using a caged litter (either carried by personnel down the access way or by crane over the roof) was initially developed by the general contractor and approved by the joint venture.
Early in the preconstruction phase, the safety director for HRC/TRI had several informal technical meetings with Titan management, representatives of the Operating Engineers and Sheet Metal Worker’s locals as well as Pat Griffin and Dave Grafton from the Braintree OSHA area office. In these meetings, all the project’s job safety issues were discussed, modified for site conditions and thoroughly reviewed for OSHA compliance. Several advisory recommendations were made by the compliance officers to facilitate the standard operating procedures on the job, including:
Safe roof access from the mechanical roof below was to be provided by an 8-foot-by-12-foot system scaffold tower with integral stairs and railings
A fall protection program was instituted that includes a guardrail system with 1/2-inch aircraft cable top rail at 42-inch-high run through 2-inch-by-2-inch-by-1/4-inch angle iron anchored to the 24-inch high parapet (mid rail and toe board) at 10 feet on center. A mid-rail cable was installed at 21 inches on the guardrails over the barrel gable ends.
The crane lift pad was relocated to eliminate the need to swing the boom, reducing pedestrian hazards inside the controlled access lift zone.
Minimum acceptable criteria were established for crane site compaction tests.
A controlled hoisting access zone was established below for the rigger/oiler to maintain site security
In accordance to its standards, OSHA would not allow any personnel inside the unit while it is suspended by the crane. On the first day the mill had a mechanical failure which required the on-roof operator to manually trip an emergency off button with 4-foot rod then hand-shear the first half of the panel without ever entering the box.
All the union labor on this job was drug-tested prior to hire, as per the joint venture’s safety and health program in which all of the workers were trained. In a relatively short period, the joint venture had great success in implementing a new and vigorous safety culture on the job. With the continuous employee input, an empowered safety committee and ultimate support of management, the joint venture’s priorities are becoming, in order, safety, quality and productivity. From the CEO on down, there simply is no compromise on safety. Their untiring attempts will ultimately result in zero accidents, an ever-decreasing accident rate and experience modification rate, lower workers compensation payments (eventual self-insurance) and higher profitability.
Up to the submission date of this article, there have been only two weather-related, non-emergency roof evacuations into the building. Boston weather is monitored using an on-site weather station, and Accu-view Doppler Radar Instrument readings are recorded at pre-shift every workday by the project supervisor. Emergency NOAH weather radio and phone alerts are available from the general contractor.
The material-handling hazards that are greatly reduced or avoided completely include struck-by, caught in/between and ergonomic. In combination with high-tac, cut-resistant gloves for the sheet metal workers, the forming mill also de-burrs and dulls the edges of the aluminum stock, thus eliminating lacerations.
According to the sheet metal foreman, some of the best site-specific safety suggestions are made by crewmembers during the weekly safety “toolbox” talks. One such safety suggestion was the use of Tingley® rubber overshoes over their workboots to significantly improve traction and steady footing on damp, slippery membranes and metal. Roof edge change-out also prevented tracking clay mud up from the yard and roads onto the roof deck. Security and productivity were immediately and visibly increased.
This type of employee participation in their own health and safety is just one of the benefits that HRC and TRI are achieving in this joint venture. The safety vigilance on a project the size and scope of the Boston Convention Center is certainly intense and ongoing, but the results indicate a healthier and more profitable partnership between labor and management as well as general contractor and subcontractor. The project safety director holds monthly on-site project safety meetings where everyone’s input is encouraged. At these meetings various existing and potential roof hazards are discussed and appropriate controls anticipated and implemented without putting schedule or productivity ahead of worker safety.