Polyroof were once again successful at an industry awards event, scooping the LRWA Project over 1,000m2 Award at the Titanic Hotel, Liverpool last month. Working with Williams Roofing Contractors Ltd of Eastleigh, Hampshire, the winning project involved the refurbishment of a large water treatment plant that imposed stringent environmental and performance requirements. The outstanding workmanship and attention to detail by the Polyroof approved contractor during this large scale installation allowed this project to really stand out from the crowd. The below is a case study for this award-winning project, highlighting the many challenges and how they were overcome through innovation, workmanship and product choice.

Following a survey of the roof area conducted by Williams Roofing and Polyroof Technical Services, a detailed report was carried out after which a bespoke specification was produced and handed to the client. This document detailed a comprehensive set of recommendations for solving the issues that had arisen due to the aged condition of the roof coverings.

The client, satisfied that the solution proposed would provide the lasting peace of mind they were looking for, awarded the contract to Williams Roofing Contractors Ltd to install the Polyroof Protec system.

Southern Water Otterbourne

Project Size: 2000m2
Approved Contractor: Williams Roofing Contractors
Location: Winchester
Project Type: Refurbishment
Sector: Utilities
System Installed: Protec System


There were many challenges on this project as this was a live ‘Clean Water’ environment site, so all Williams Roofing Contractor staff on the project had to have the EUSR National Water Hygiene Cards and be fully inducted by Southern Water’s high standards.

Working within these type of environments brings additional Health & Safety implications as the National Water Hygiene scheme is in place to ensure the protection of public health and promote safe drinking water practices. Further risks had to be considered and covered including the risk of working over open water areas with additional buoyancy aids on site to reduce the risks as described under CDM regulations.

Williams Roofing Contractors Ltd had to be especially vigilant providing additional protection to ensure that no potential contamination or spills caused any contaminants to the clean water processes/water courses and environment with additional spill kits on hand.


Due to the varying conditions of the roof construction(s)/substrates the preparation had to be thought through thoroughly. Certain roof areas needed to be scarified which would have caused reverberations through the roof/concrete deck. This would have possibly created contaminants by spooling of concrete/debris/dust to within the MF Compound Water Lanes/Tanks. After various meetings, additional protection was utilised and installed within the buildings above the Water Lanes/Tanks to ensure that any spooling of concrete/particles did not enter into the ‘Clean Water’ process as this could potentially have blocked the screens (filters). If the Water Lanes/Tanks had become contaminated during our works, the whole ’Clean Water’ process/system, may have had to be temporarily shut down.

Moisture was discovered beneath an identified area of one of the roof areas and the specification on this particular roof was changed with the client’s agreement. To aid in the dissipation of the moisture ’Mushroom’ vents were installed. This again was of huge benefit to the client because if the roof had been required to be completely stripped, the Water Process would have had to be temporarily suspended so this saved a huge amount of disruption to the ‘Clean Water’ process and the Client.

The River Intake Building was constructed of a ’Barrel Vault’ type construction which had a concrete rooflight detail with glazing blocks. Again the client wanted to keep the ‘Lux’ levels in the building but needed the roof to be watertight and guaranteed.

In order to provide a solution for this difficult challenge, the Polyroof Transglaze PU liquid was specified in conjunction with the Protec system. Transglaze is a translucent waterproofing system that permits the passage of light through the membrane into the interior of the building, minimising any reduction in light into the interior of the building. This system was carefully applied to the glazed blocks before the Protec system was laid over the concrete sections to complete the seamless waterproofing on these details.

Another complex detail to be overcome was the many internal parapet walls that divided the roof areas above one of the buildings. To ensure that water could drain from the roof, there were numerous through-wall outlets positioned at the bottom of these parapet walls, each one needing to be made completely watertight. This was one of the many reasons why a liquid system was preferable; by using appropriate small roller application tools, Williams Roofing Contractors Ltd were able to fully seal inside each on of these outlets.

With respect to the parapet walls themselves, the multi-surface ability of Protec meant that the system could be applied directly to the brickwork, saving the client further costs through eliminating the need to over-board. A key advantage of Protec is its high thixotropy, meaning it can easily coat vertical surfaces without the need for any additional thixo additives.

As you can see within the photographs some of the detailing within the various roof areas was very intrinsic, especially the MF Compound Building which had two number banks of ‘Sump’ type details present. A liquid applied membrane was the preferred product by the nature of the detail and undulations within roof construction, the client required a guarantee that would include difficult details.

The works were completed to an extremely high standard. The result was the full encapsulation of the roof areas, without a single detail left exposed to the elements. Following a final inspection by Polyroof, the roof was signed off for guarantee and the client was extremely pleased with the service and product they received.

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