The project consisted of two similar flat roof areas totalling 1,100m2 above high rise residential blocks in a city centre location. The existing roofs were an inverted roof design that had been waterproofed with single-ply that had failed prematurely. Numerous short term, localised repairs had failed to stop the water ingress and leaks had been a long-term problem. It would have been impractical to remove the tons and tons of ballast and insulation from the top of the high-rise building and it was imperative to the client that removal/replacement works were not involved at all. This meant that the waterproofing solution had to be able to be applied directly to the existing single-ply coverings.

However, a report from an independent consultant commissioned by the client identified a problematic challenge with an overlay option. The existing falls of the roof were assessed to be poor and so standing water would be an issue for any new waterproof covering. The report concluded that this would reduce for lifespan of an overlay waterproofing system and so was advised against. The client initially thought this to be a stumbling block and that costly and impractical modifications to the roof would need to be made.


Having worked with Polyroof and scores of other projects, the client turned to Polyroof Technical Services for a solution that could meet their stringent criteria. Following on from the preliminary discussions Polyroof’s technical department that assessed the site, took core samples and then provided a suitable specification to overlay the roof with the Protec system.

The BBA certification of the Protec system specifically covers use for zero falls (completely flat) applications, meaning the client had absolute peace of mind that standing water would not be a detriment to the integrity of the waterproofing system. The client was able to achieve the original objective of an overlay system and benefited from the associated cost and time savings. Furthermore, the BBA certificate states that when used in inverted roof scenarios the lifespan of the Protec system is as long as the design life of the roof.

Work started was started by J R Flat Roofing, a Polyroof approved contractor with national coverage, having to remove the pebbles and insulation and place to one-side in four separate phases to each block 140m2 at a time, exposing the single-ply membrane to which the Protec system was directly applied. Due to Protec's rapid cure and walk-on times (30-60 mins dependent on conditions), the system is ideal for larger, phased refurbishment as distinct sections of the roof can be made waterproof with the full Protec system in one day. When carrying out the next section, the new Protec membrane forms a totally seamless and watertight joint to the existing Protec-covered areas.


Another objective was to reuse the original inverted insulation and ballast pebbles, this was cost saving and negated the need for the lifting logistics that would have been involved in bringing the ballast to ground level. Additionally it made the process as environmentally compliant as possible by keeping waste to a minimum. The insulation and pebbles were re-applied in its original format and, due to the weight of the pebbles, was a mammoth task that required three miniveyors to help with the handling. A series of special aluminium breather vents were also fitted down to the concrete slab roof substrate to enable the surface to dry out over a period of 12 months.

The whole job was completed in three weeks and the client was delighted with the finished work. With a 20 year insurance back-guarantee and a maintenance-free waterproof membrane that will last as long as the roof stands, the client was once again left with total peace of mind that their buildings could not be better protected.