Complex Restoration Requires Specialized Scaffold System
October 28, 2016
Working on a complex curtain wall restoration project at Milliken Mills Community Centre in Markham required multiple trade skills — and a special emphasis on safety.
On this project, contractor BRC Restoration employed a unique scaffolding system designed to work with the unusual architecture of the building.
The project, valued at just over $200,000, involved a masonry curtain wall repair and structural steel repair of a two-storey architectural feature wall constructed above the roof line. Although the building is just over 30 years old, flaws in the curtain wall system had become obvious as driving rain was penetrating the building and leaking into the centre’s library.
"There’s a masonry band directly above the curtain wall and columns," says Arran Brannigan, vice-president with BRC Restoration.
"We needed to strip off the masonry to expose the back-up, and then replace and repair structural steel components. The shelf angles were corroded and not properly installed, and we were replacing them with hot dip galvanized components to meet the current building code."
Below the curtain wall, BRC removed all of the snap caps and pressure plates and replaced them with anchors of anodized aluminum and applied new sealant. The masonry tie system was also inadequate with several ties missing or improperly installed.
"Putting the wall back together, we upgraded the insulation with rigid board and included a new membrane air vapour barrier," says Brannigan.
"BLOK-LOK masonry ties were used to stabilize the masonry system, but as a retrofit we had to drill pilot holes through the masonry at a major angle that was very unusual. We then had to use specialty self-tapping screws to install the anchors, which were made of stainless steel and brass. It wasn’t an off-the-shelf solution."
Working with BRC on the contract were prime consultant TSS Building Science and structural engineer Read Jones Christoffersen Consulting Engineers (RJC).
"It was tricky working within the existing steel framing, so we brought in RJC to do the structural design for the shelf angles and provide some practical solutions," says Brannigan.
However, an unusually shaped roof element jutting out of the feature wall and angling forward at the base required special consideration.
"Safety is everything for us," says Brannigan.
"We all have scaffold training but this wasn’t like traditional scaffolding that you build plumb. We had the challenge of contending with this sloped feature. It’s a requirement of the Occupational Health and Safety Act that any scaffolding over 50 feet requires a design approved by a professional engineer. In this case we were under no obligation to do that, but we wanted to invest the additional money to bring in a structural engineer to do this right and to protect workers and library patrons on the other side of the glass."
With the scaffolding methodology left up to the contractor, BRC obtained the services of CCI Group Inc. According to BRC’s design approved by the engineers, workers installed wood sills on the top of the sloping roof, then nailed the feet of the scaffolding passing over that area to the board. Horizontal and diagonal bracing extended from that portion of the scaffold to additional scaffolding fixed to the building roof.
"The scaffolding performed perfectly," says Brannigan.
"Part of the success of a project like this is knowing how to select the right team to leverage the needed expertise."
The project, which began in April, was completed on schedule in late September.