Case Study:Heritage Window Revival: Navigating Access and Restoration on a Landmark London Building

A Grade II listed commercial building in the heart of the City of London required urgent care for its historic facade. The original timber sash windows were deteriorating, and the stone sills were cracked and weathered. The client approached us to deliver a specialist restoration that would meet standards defined by the grade II listed status and navigate the complex access requirements of this central London site.

The Site

Built in 1926, this multi-storey, Grade II listed commercial property stands as a proud example of early 20th-century architecture amidst the modern skyline of the City. Nestled amongst the eastern tower cluster, it sits just north of Leadenhall Street, a stone’s throw from the iconic Leadenhall Market and Lloyd’s of London. The building’s prestigious location and historical significance require a meticulous approach to maintenance.

Following a major internal refurbishment, which included the transformation of its office spaces and the reception area with concierge service, the client sought to bring the exterior up to the same high standard. Subject to oversight by the City of London Heritage Committee, every element of the work had to be completed with exceptional care and in keeping with the building’s listed status.

The Challenge

The client required professional restoration on heritage sash windows across several elevations and decorative works across an additional 100+ windows. Many of the stone sills had developed deep weather-related cracks, and the entire facade had not seen a professional clean in some time. Further complicating the project were significant access issues, including wind deflector fins that obstructed rope access, and overhanging facade features that rendered abseiling alone unworkable on certain elevations.

Our Solution 

We proposed a hybrid access solution using a combination of tower scaffolding and rope access techniques. For rope access, we deployed temporary deadweight anchors and A-frames installed on the roof, allowing our IRATA-certified technicians to abseil down safely. On elevations where abseiling was not viable, tower scaffolding was introduced. This flexible method minimised disruption while keeping the project cost-effective.

The Process 

Over 3 months, our skilled operatives completed the following works:

Timber Window Repairs

We repaired and redecorated 19 wooden sash windows using splice repairs. Where necessary, decayed sections were removed and replaced with new hardwood splices. We used a two-part resin repair system for minor damage, followed by priming and repainting with a durable exterior-grade paint to match the original finish.

Stone Sill Restoration

Our specialist stonemasons cleaned out weathered and cracked mortar from the original stone sills. We then carried out stone repairs using a colour-matched lime-based mortar, designed to preserve the appearance and breathability of the substrate.

Final Window Clean

Towards the end of the project, we carried out a full builder’s clean of approximately 120 windows. This included removing years of limescale, construction debris and other stubborn soiling. Our window cleaning operatives used professional-grade solutions and tools to deliver a spotless final result.

The Challenges

A key complexity on this project was the building's architectural features. Wind deflector fins had to be temporarily removed by the client to allow the safe placement of deadweight trolleys for us to abseil from. Additionally, overhangs on the facade meant rope access alone couldn't provide safe proximity to all windows. Our hybrid access methodology ensured that every window could be safely reached and restored.

The Result

Following our restoration and cleaning works, the building was visually transformed. The timber sash windows were restored to their original character, the stone sills now free of visible cracking, and the entire window line gleamed after our deep clean. This careful restoration has extended the life of the facade and preserved the property's heritage value for years to come.

This project exemplifies our ability to blend traditional craftsmanship with modern access solutions. Whether it’s restoring sash windows, repairing stone sills or carrying out final cleaning, we ensure heritage standards are met with efficiency and integrity.

Get in touch to learn how Spectrum can help preserve your building’s legacy.