McGee House

Project Size: 223m2

Approved Contractor: MLG Building Contractors

Location: Chepstow

Project Type: New Build

Sector: Housing

System Installed: Protec System

McGee House

The client, Sarah Browne Architecture, first initiated contact with Polyroof through a website enquiry, seeking both a project specification, and guidance on the most suitable liquid system for this striking project that stands within the esteemed Steep Street area of Chepstow, Gwent. This new build 223m² roof, with a distinctive 10-degree mono-pitch rectangular shape, integrates a comprehensive green roof system, extended overhangs, onboard gutters, and a photovoltaic (PV) array on the front side. The architectural design of McGee house aligns with the key principles of a Passivhaus, providing a building that provides high levels of thermal comfort all year round, creating a warm, comfortable, healthy home to live in.

LRWA Award Finalist: Liquid Roofing Project of the Year in a Buried Application

Passivhaus is achieved through the 5 key principles:

  • Highly levels of insulation
  • Prioritising airtightness
  • Addressing thermal bridging
  • High quality triple glazed windows & doors
  • MVHR (Mechanical Ventilation with Heat Recovery)

After receiving an initial project overview alongside indicative drawings from the client, Polyroof technical services began to advise on the best steps forward for the unique requirements of the roofing system. The team offered several recommendations and presented the BBA Approved Protec Warm Roof System, along with a new build outline specification and a roster of Polyroof approved contractors. The main recommendation, pivotal to the project, involved reconsidering the initially specified prefabricated cassette system with Polyroof’s technical team proposing a shift towards a true warm roof build-up. Subsequent adjustments to drawings and specifications were made to align with this refined approach. Further assistance was provided in the form of a thermal calculation and condensation risk analysis. Given the distinctive roof shape coupled with substantial 200mm insulation, a wind uplift calculation was crucial in determining bonding requirements.

Experienced Polyroof approved contractor, MLG Building Contractors, were selected by the client to carry out the project. The MLG team created a bespoke timber frame which was then boarded with smart ply and any joints taped up. This recessed spreadsheet timber deck would eventually accommodate the warm roof build up. Custom cast iron supports were strategically installed to uphold the roof perimeter canopy, which was subsequently boarded with OSB3. The application of a Polyroof foil-faced SA Vapour Barrier, 200mm of Polyroof Tissue Therm insulation, and Polyroof SA Sand-faced carrier layer laid the groundwork for the subsequent application of the BBA Approved Polyroof Protec System. The application of the Protec System involved the first coat being applied with 450gsm² mat, followed by snagging and the subsequent application of the second coat. The resulting seamless finish and the meticulous attention to detail were evident in the final project images.

Following the application of the liquid system build up, the roof was not only insulated and waterproofed, but also aesthetically enhanced with a fully established extensive ‘Sky Garden’ sedum system. This green roof system serves a multifaceted purpose, improving drainage, extending the roof’s lifespan, enhancing thermal performance, reducing carbon dioxide, supporting wildlife habitats, and contributing to improved air quality. To secure the PV cells, the hardwood blocks were encapsulated with the Protec System. Subsequently, the PV cells were then fixed mechanically to the hardwood blocks, ensuring that the fixings did not penetrate the underside of the blocks.

The photographs truely show the spectatacular finish that can be achieved using Polyroof’s liquid roofing membranes. Characterised by seamlessness, maintenance-free attributes, lightweight design, and exceptional durability, Polyroofs liquid solution served as the ideal base for the integrated green roof system. The project was executed to an exceptionally high standard, achieving full encapsulation of the roof area and canopy without compromising on any detail. Following a thorough inspection by Polyroof, the roof was officially signed off for guarantee, leaving the client exceedingly pleased with both the service and the product delivered.

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