The Host Helix building, also known as the “Helter-Skelter,” was a unique and striking structure built in 2011 with stunning views of North London and Wembley Stadium. Over time, the building experienced general wear and tear and water began to enter the buildings’ complex structure.

Polyroof Products were called in to consult with the clients and offer a seamless, encapsulated solution that could address the many unusual details associated with the building’s design.

The Solution

A full survey of the roof terrace areas was conducted by the Polyroof Technical Services, after which a bespoke specification was produced for the works. The proposal document detailed a comprehensive set of recommendations for producing a seamless solution to encapsulate the problematic roof, therefore solving the issues that had arisen over the years due to its condition and age, as well as the issues associated with the original design of the pitched, curved roof.

Polyroof SA Carrier Layer was then applied over the cement particle boards with Polyroof pre-formed GRP Drip Trims fixed to the external edge. For continuity and to create a uniform finish, the SA Carrier Layer was extended onto the main roof sections as a substrate for the Protec system.

Any details requiring local reinforcement were treated with Protec Resin and 75mm wide Polymat 450. The curing process was allowed to take place. To accommodate structural expansion / contraction movements at appropriate details, 25mm disbondment tape was installed prior to local reinforcements.

The first coat of Protec Resin and Polymat 450 was applied at a minimum coverage rate of 1.3 – 1.5Litres/m² (0.66 – 0.77m²/Litre) and was allowed to cure. To complete the system, a second coat of Protec Resin was applied at a minimum coverage rate of 0.5Litres/m² (2.0m²/Litre) and was allowed to cure.


Such an iconic building in the local community, the client wanted to protect the original aspects of the building to the fullest extent, so the Protec system installed at the perimeter was color-matched to the original blue and grey colours. This was achieved by blending pigments until they matched the desired colors, in turn the pigment was then blended into the Protec resin before application. The survey revealed concerns about the original building designs from 2011 and the roof’s drainage system. Due to the roof’s pitch, rainwater was cascading down the curved slopes at high velocity and causing water to bounce into the building under the original capping.

After many discussions between the main contractor and Polyroof, as well as the provider of the external cladding, it was agreed that the perimeter detail needed to be encapsulated with the new waterproofing system to prevent further water ingress. Fire-retardant cement particle boards were fixed to the internal and top faces of the external parapet walls, and the Polyroof SA Carrier Layer was applied over them with Polyroof pre-formed GRP Drip Trims fixed to the external edge.

The Protec System was then applied to encapsulate the entire parapet detail, meaning its waterproof integrity would be covered under the Polyroof Guarantee. The curvature of the building added complexity to this process, and the contractor took great care in cutting the trims to size and fixing them to the external edge to ensure they followed the profile of the structure. Due to the building’s height, all the trims were face-fixed to prevent wind uplift.


In order to improve drainage and prevent water from accumulating in hotspot areas of the roof, the contractors were instructed to install new internal curved gutter channels at the point where the roof and building met. These channels were designed to have a sufficient height and angle to effectively direct rainwater towards the outlets, preventing water from pooling on the roof. However, the installation process was made more complex due to the curved nature of the building’s architecture, which required careful measurement and customization of the gutter channels to fit the unique shape of the building.

Additionally, the contractors had to consider the many joins of the gutters and how they would hold up to the elements over time as the building structure expands, contracts and moves. Extra steps were taken to ensure the gutters liquid membrane was properly sealed and secured to prevent leaks.

The contractors were instructed to repair all protrusion and mansafe post details as necessary in order to allow the Protec System to be installed to a minimum height of 150mm, and to terminate it underneath a suitable weathering flange or jubilee clip. In addition, all right angles were to be reinforced with double taping. Any protrusions that were liable to significant movement was required to have disbondment i.e., bond break, tape applied to it to stop the external coating from stressing on expansion. Furthermore, all pipes were to be abraded, solvent wiped, and where necessary, primed in accordance with the Polyroof coatings manual. A flashing detail was also to be created with a weathering flange or seal.

All outlets were inspected to ensure that they were functioning properly. Any outlets that were deemed unsuitable were replaced with new ones. The outlets were cleaned, prepared, and primed as necessary. The Protec system was then dressed into the outlets as far as was practical. The inspection and replacement of the outlets and the preparation of the Protec system helped to ensure that the drainage system functioned effectively.


The refurbishment of the roof was completed within the client’s target timeframe and budget. Following a final inspection by Polyroof Technical Services, which highlighted quality workmanship of Tower Asphalt Ltd, the client received Polyroof’s trusted Accredited System Guarantee and now has the peace of mind the roof will be leak-free for decades to come.

The Host Helix Student Accommodation project, completed in collaboration with Tower Asphalt Ltd , won the coveted Liquid Roofing Project of the Year over 1,000 m² category and was also a finalist at the National Roofing Awards 2023.

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