Stuart Hicks, from cold liquid-applied wet-on-wet waterproofing specialist, Kemper System, discusses the problems caused by a failed waterproofing system at a luxury residential development near Brighton and outlines the project undertaken to replace it.
You only need to see a picture of The Grand Ocean Hotel in Saltdean, near Brighton, in its heyday to capture a glimpse of a bygone era of glamourous seaside elegance in surroundings that epitomised contemporary design.
The Grade II listed building first opened on a four-acre site in 1938 with 344 bedrooms and a dining hall that could seat 300. Its crescent-shaped white facade with a bulbous central pillar makes it a classic of Art Deco architectural design.
Now the central building from which a development of luxury apartments takes its name, this costal landmark has had a varied history, which includes being requisitioned by the Auxillary Fire Service during World War II, used as a Fire Service college after the war and becoming a popular honeymoon destination in the 1950s after it was acquired by holiday camp pioneer, Billy Butlin in 1953.
While Butlins sold the iconic building in 1999, it remained open as a hotel until 2005 when planning permission was granted to convert it into luxury apartments with an additional four new build apartment blocks within the grounds.
Design of the new build blocks was in-keeping with the main hotel building and every attention was taken to preserve the original structure in line with its listed status. However, problems with the integrity of the originally specified waterproofing system became apparent even before refurbishment of the main hotel building had been completed. This led to a change of roofing contractor and, eventually, a replacement roofing system too.
Both the existing hotel building and the four new builds are of a flat roof design and the architect had specified a liquid waterproofing membrane to maintain the listed building’s appearance while providing a neat finish for the new builds.
Unfortunately, the system originally selected was not robust enough to adhere seamlessly to both the roof and all upstands and outlets as a permanently elastic, monolithic membrane. The development’s coastal location also required a more durable and flexible membrane that could withstand a moist and salty atmosphere and high UV levels.
When the integrity of the waterproofing membrane on the four new build structures was first compromised, the assumption was made that the issue lay with the quality of installation rather than the suitability of the membrane. A new roofing contractor was brought in to carry out repairs to the membrane and repairs were carried out using the same product because it was still under warranty.
The majority of the problems with the roofing material were around the upstands, where the originally specified roofing system had not adhered sufficiently to the vertical surfaces and was not flexible enough to cope with structural movement. Following repairs, the problems recurred.
The roofing contractor turned to a cold-applied wet-on-wet waterproofing system that the company had used on a wide variety of construction projects in the past. The company recommended the new system to the architect for remedial works to both the new builds and the former hotel building, including the roof areas, balconies and terraces.
The decision was taken to install the replacement waterproofing system as an overlay onto the existing failed membrane wherever possible. Where an overlay wasn’t viable, the contractor stripped out the existing and replaced it with the new flexible liquid membrane.
The existing roof build up for the new build apartment blocks was an inverted roof with the originally specified membrane installed beneath the insulation. The roofing team removed the paving slabs and green roof medium along with the insulation and, where possible, this was stored for re-use in the new roof build up.
The company then had to carry out preparation and cleaning of the roof surface before installation of the new membrane could begin. In the areas around the upstands where the failed membrane had not bonded, the contractor simply pulled off the damaged membrane.
Once the new waterproofing system was in place, the insulation, slabs and green roof medium that had been removed to access the failed waterproofing membrane were then reinstated to complete the roof.
The build-up for each of the new builds’ terraces was the same as the main roof and the same process and materials were used. The paving slabs were removed for re-use and the failed membrane was overlaid with the new system.
For the roof and balconies of the former hotel building, however, the damage caused by the failed waterproofing membrane was even more significant because the original roof build-up was not inverted.
The roofing contractor tackled the balconies first and had to strip out the entire roof build-up of paving slabs, waterproofing membrane and insulation. Here, not only had the originally specified membrane failed but, as a result of the water ingress, the insulation below it had begun to rot too.
Following strip out, the concrete substrate was allowed to dry on each balcony before the new waterproofing could be installed. To save time, the build-up for each balcony was then reinstated as an inverted warm roof.
The same primer, resin and fleece waterproofing system was used for the balconies of the refurbished hotel as for the new build apartment blocks and the membrane was allowed to cure before new insulation and paving slabs or decking were installed.
The installation team then moved onto the 8,500m2 former hotel roof, which comprises five ‘fingers’ with a central core. Water ingress around the roof outlets where the failed membrane had not bonded properly meant that the recently installed warm roof insulation was already sodden and the roof had to be stripped back to the vapour barrier.
To aid water run-off in the future, a tapered insulation scheme was designed which introduced a slight pitch to each roof section. These pre-primed sections were then fixed to the substrate and joint sealed before application of the new waterproofing membrane began.
The latest residents have now moved into the historic former hotel, continuing its journey from hotel, to fire service training, holiday camp and, finally, luxury homes.