Tony Betts, MD of sealant application specialist MHD Group
What was the problem?
The £430m, 800-bed hospital is being built by Carillion for the North Bristol NHS Trust and is due for completion in 2014. Reconstructed stone cladding is being installed on all the external walls, which had to be sealed using a high-performance weatherproof joint sealant. Access to the facades was restricted at ground level due to ongoing road works and ground works, materials deliveries and the site’s already tight footprint, so there wasn’t enough space for us to park a cherry picker.
What was your approach?
The roof was already built, so we were able to deploy a team of trained abseilers, who lowered themselves on ropes attached to an aluminium support frame held in position on the roof. We had two guys abseiling at a time and a technician on the roof lining up the ropes, checking safety and ensuring that no one tampered with the ropes. The abseilers used suckers to anchor their ropes into position, then applied the Sikaflex-Pro 2HP sealant to the 20mm joints between each precast concrete panel and the stone slab on the front. Each man was able to complete about 25m2 of cladding a day.
What was the biggest challenge?
Coordinating with the roofing contractor, which was installing upstands on roofing panels and tarmac coating the roof. It required daily meetings to ensure we were always launching from a different part of the roof. Carillion was very strict on quality, we had to ensure that work was carried out at the correct temperature — the mastic will not seal unless it is above 5oC and they even drilled holes to insert a camera to check our jointing behind the panels.
Are there any drawbacks with abseiling?
Neatness is more of a challenge when hanging from a building, especially in the wind or rain, but our operatives undergo five years of training and can handle all types of problem, whether it’s capping that needs screwing into curtain walling, painting drainpipes, or sealing joints under balconies.
