anchester’s commercial office stock has been transformed over the past 20 years. The city’s traditional Victorian-built environment remains and has been joined by world-class architecture with huge regeneration projects, such as Spinningfields, creating whole new business districts.
It’s not just the historic and the contemporary that have joined forces to create an eclectic property landscape in Manchester; some of the city’s tired, mid-century office buildings have also been upgraded and updated to meet the needs of post-Millennium occupiers.
One of these is Piccadilly Gate. Envisaged as a new ‘gateway’ landmark as visitors arrive at the city’s main Piccadilly station by train, the 10-storey building was refurbished in 2010, transforming the 1960s-built ‘Rail House’ into an office building that complements the city’s ambition and striking urban landscape.
Since the refurbishment, it has not only become one of the most prominent office buildings in Manchester but is also home to Government departments based in the North West. Boasting the longest escalators in Europe when it was completed, the refurbished building achieved a BREEAM ‘Excellent’ rating on completion, with a green roof on level three contributing to its accreditation.
Unfortunately, however, the single-ply membrane specified for the 2010 refurbishment failed long before the end of its predicted service life due to installation issues. This not only affected the level three green roof but also the roof on level 10, where the building’s extensive air handling plant is located and the level four roof, which sits above the building’s giant escalators.
To address these issues, Piccadilly Gate’s Building Surveyor, Abigail McArdle, took advice on the best way to address the issues within a fully occupied building. She brought in building technology and facade consultant, Alan Brookes, which recommended the installation of a Kemperol cold-applied liquid waterproofing system as an overlay, providing a solution that would minimise disruption while offering an excellent service life.
Minimum disruption
While leaks on all four roofs needed to be addressed, it was the leaks on the level four roof that were most problematic. Here, two rainwater outlets had been incorrectly installed and had not been sealed by the original waterproofing membrane. As a result, they had leaked from the first day of occupation, which had begun to cause unsightly staining of the ceiling tiles above the escalators, where it was very noticeable to both occupants and visitors.
Meanwhile, seam integrity issues on the level 10 roof were exacerbated by a drainage channel and the level three green roof installation made it difficult to investigate the cause or extent of the membrane failure beneath it.
Abigail McArdle comments: “The idea of using a wet-on-wet liquid membrane as an overlay was very attractive because it meant we could avoid all the disruption and expense of a strip-out while replacing the existing system with an alternative that has no seams and could not, therefore, be vulnerable to a repeat of the issue.
“The fact that the Kemperol system has a 25-year, BBA-accredited service life was also very attractive. We had the additional peace of mind of knowing that any repairs could be carried out by simply cutting out the affected area of membrane and resealing it.”
Castle Contractors was brought in to carry out the work and collaborated with Kemper System to finalise the specification for the overlay. While Kemperol V210 was selected for the level three and level four roofs, the decision was taken to use solvent-free Kemperol 2K-PUR for the level 10 roof due to the location of the air handling plant.
Abigail continues: “There is substantial air intake at level 10 and we were keen to avoid any nuisance odours for the building’s occupiers. Because Kemperol 2K-PUR is an odourless system, it completely avoided this potential issue.”
Flexible installation
Kemperol 2K-PUR was also an ideal solution for the vertical surfaces of the drainage channel on the level 10 roof.
After cleaning and preparing the existing roof surface, Castle Contractors applied a Kempertec primer before applying the Kemperol 2K-PUR resin in a single wet-on-wet process. The Kemperol 2K-PUR resin was applied to the substrate followed by a flexible reinforcement fleece, which was laid directly onto the wet resin. This was immediately followed by more resin to ensure complete saturation of the reinforcement fleece. Once cured, the resin forms a seamless, elastomeric waterproof membrane that cannot delaminate, is UV stable and bonds directly to the substrate.
On the level four roof, Castle Contractors began by removing the failed rainwater outlets and replacing them before preparing the roof surface and applying the cold liquid system in the same wet-on-wet process. This time, however, Kemperol V210 was used and applied in the same configuration of primer, resin-fleece-resin.
For the level three roof, the contractor had to remove the green roof before the overlay could be applied to the existing failed membrane. However, retaining the green roof was an important part of the brief. As a result, Castle Contractors carefully took up half of the green roof and prepared the roof surface beneath it, applying the Kemperol V210 membrane in a single wet-on-wet process. Once the new membrane had cured, the first section of green roof was replaced and the process was repeated with the remaining half until the whole level three roof had been reinstated.
Abigail adds: “Kemperol V210 has been used extensively in green roof build-ups and we were confident that using a waterproofing membrane with proven root resistance would provide a long-term solution for the level three roof.”
Long-term solution
The roof refurbishment was carried out at three different levels with no disruption to the building or its occupiers and no aesthetic changes to its appearance. The result is an overlay scheme that has not only put an end to the damage that leaks were causing but has also removed any possibility that similar issues might recur.
