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Case Study

Replacing a failing slate roof with a high-performance system designed for long-term durability.

Halton Mills, a residential apartment building, required a complete re-roof after years of persistent water ingress caused widespread deterioration of the original slate roof. The ongoing leaks left the building's lift out of service for almost three years, significantly affecting residents' quality of life. The project became far more than a roof replacement. It was an opportunity to resolve long-standing defects, restore the building's performance and provide residents with a durable roofing solution designed to protect their homes for decades to come. The completed scheme combines the timeless appearance and durability of traditional natural slate with a fully integrated Permavent roofing system, providing a robust, well-ventilated and future-proof solution. Halton Mills now benefits from a resilient roofing system that not only preserves the building's character but also provides the reliability, safety and performance expected of a modern residential development.

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Location

Halton Mills, Lancaster

The Project

What began as a relatively straightforward roofing repair quickly evolved into a complex refurbishment programme involving structural strengthening, fire engineering upgrades, a complete redesign of the roof ventilation strategy and the replacement of unsuitable roof coverings. Given the size of the occupied residential building, the project required an extensive scaffold design covering approximately 1,000m², complete with a temporary roof to maintain continuous weather protection throughout the works. Once the existing roof coverings were removed, it became clear that the Brazilian slate could not be reused in accordance with NFRC guidance. This transformed the original repair scheme into a full re-roofing project. Further investigations revealed significant structural defects requiring extensive strengthening works. The building’s 900mm eaves and gable overhangs had experienced years of wind uplift damage affecting both the roof and surrounding masonry. To restore long-term stability, GAP Roofing installed hundreds of steel angles to reinforce the eaves and gable ladders, securely tying each element back into the timber frame.

Permavent in Action

Natural slate was selected to provide a durable, high-quality roof finish, complemented by an integrated Permavent roofing system designed to deliver long-term weather protection and moisture management.
Permavent DRY+ was specified as the vapour permeable underlay, creating an effective secondary weather barrier while allowing moisture to escape from the roof construction. This helps reduce the risk of condensation and supports the long-term durability of the roof. Installed beneath every slate, Permavent Easy Slate provided enhanced secondary weather protection by sealing the perp joints between adjacent slates, helping to prevent wind-driven rain from penetrating beneath the roof covering. Permavent Permatac® Butyl Tape was also incorporated to create a watertight seal around nail penetrations, enabling the completed roof to meet the performance requirements for a 40-year warranty.

The integrated Permavent system also proved invaluable in overcoming several unforeseen site challenges. Hidden fire compartmentation interrupted planned ventilation routes, while varying roof details required bespoke solutions. Products including the Universal Low Pitch Vent, Over Fascia Vent and Universal Ridge Kit enabled effective ventilation to be maintained throughout the roof despite these constraints, ensuring the completed system met both performance and durability requirements.

By combining traditional natural slate with a fully integrated Permavent roofing system, GAP Roofing delivered a technically robust solution capable of protecting the building for decades to come. Most importantly, the project brought an end to years of water ingress, restored confidence in the building and significantly improved everyday life for its residents.

“The products performed exceptionally well in a complex roof environment, particularly where ventilation, low‑pitch detailing, and fire‑compartment interactions required careful coordination.”

Contracts Manager, GAP Roofing

“Whilst this may not have been the largest project in financial terms, it stands out as one of the most rewarding. Its success lies in the determination of everyone involved to overcome complex logistical and technical challenges while never compromising on workmanship or quality. Halton Mills is a perfect example of how collaborative working, expert design, and first-class roofing craftsmanship can deliver an outstanding outcome for both the building and its residents. This project is a story of resilience, partnership, and pride in quality, a roof that not only protects a residential building but also demonstrates the very best of the slate roofing industry.”

Homestead Consultancy Services Ltd