A jumper for buildings

After years of trying to plug the holes in two of Oldham's best-known landmarks, the Crossbank and Summervale tower blocks, Colin Leddie finally gave up. The project manager of First Choice Homes, the landlord that manages Oldham's ex-council stock, called a halt to repairs and took an entirely different approach.

Although the blocks leaked only in bad weather, that's something Oldham gets plenty of. The Bison hollowcore floor slabs allow rainwater to track through them, so a leak can show up anywhere in the building by running through the slabs and down junctions with crosswalls. This made it impossible to locate where rainwater was getting in. "Like trying to find a needle in a haystack," says Leddie.

Instead, he decided to get around the problem by sealing the high-rises in Dryvit Outsulation – an overcladding system that will also insulate the buildings to modern standards, weatherproof them and give them a brand-new look. Although there are only a limited number of Outsulation installations in the UK, it has been used in the US for 40 years.

Outsulation is a barrier system of 1.2m by 0.6m expanded polystyrene boards covered with a 4mm-thick glass fibre mesh to give it rigidity, and an acrylic finishing coat to give a choice of texture and colour as well as protection. There are five standard textures, created by trowelling in aggregate, and 350-odd colours; custom textures and colour matches are available. Outsulation can also be moulded.

The new U-value of the blocks will be 0.28W/m²K, generating predicted savings in fuel and CO₂ emissions up to 20%. Insulating the outermost layer of a building with an external insulation system avoids cold bridging around windows and doors and the junctions of walls with floors and roofs. The warm wall construction also eliminates condensation. And in the case of Oldham's tower blocks, the Outsulation will put a stop to those leaks.

Enquiry number 202