Landmark Windows recently partnered with an architect to undertake a comprehensive property renovation in Hampstead, London. This prestigious project involved one of our most in-demand services: double-glazed sash window replacement into fully restored original box frames.
Landmark Windows, a family-run business founded by Steve Hunt in 2003, has developed a strong reputation in the heritage timber window market, providing bespoke solutions for both domestic and commercial projects. Now joined by his two sons (Tom & Ben) and a skilled team of joiners and fitters, Steve has seen Landmark grow into a trusted name across London’s conservation areas and listed building projects.
A Perfect Fit for London’s Period Properties in Conservation Areas and Listed Buildings
Working closely with the local council and conservation authority, Landmark ensured that every detail of the renovation met strict conservation guidelines. By collaborating throughout the project, we provided all necessary technical surveys, drawings, and proposals to satisfy both the client and the regulatory bodies.
Key Concerns and Landmark’s Solutions:
Can any original elements of the windows be retained?
After conducting a full technical survey, we determined that while the original box frames could be restored, the sliding sashes had deteriorated beyond repair. Retrofitting double glazing into these old sashes would not only be costly but would also damage the original mouldings, as they were designed for single glazing. Therefore, it was more sustainable and cost-effective to install new double-glazed sashes, handcrafted to match the original period details, into the restored box frames.
Will the new windows match and look like for like?
We reassured the council and the conservation officer by providing detailed drawings and an onsite example. Landmark’s sash windows are meticulously handcrafted to replicate the original designs, including matching all existing section dimensions and detailing such as hand-cut sash horns. We also sourced traditional ironmongery, like square-end axle pulleys with weights and cords, to ensure an authentic period look. Custom tooling was commissioned to precisely match the original mouldings and profiles, showcasing our commitment to preserving the building’s historical integrity.
What construction methods are used?
We pride ourselves on using traditional joinery techniques, ensuring authenticity in every project. For this renovation, our sliding sash windows were made using wedged mortice and tenon joints—exactly as the originals were crafted. This approach meets both conservation requirements and the highest standards of durability.
Will the glazing bars be true, through bars?
Landmark uses solid through glazing bars, with individual panes of glass, just as found in the original windows. Our extensive collection of tooling profiles, including lamb’s tongue and ovolo sections, allows us to match any historical glazing bar style. For this project, we ensured the slim glazing bars were accurate to the period and met listed building demands.
What glass and glazing methods are suitable for listed buildings?
When working in listed properties, energy-efficient glazing options are often limited. After reviewing the options with the conservation officer, it was decided that Heritage slimline double glazing would provide an optimal balance of thermal efficiency and historical accuracy. While Fineo vacuum glazing was considered, it was deemed unnecessary due to the property’s age and the likelihood of heat loss through its uninsulated walls. The approval for double glazing came with the condition that a traditional putty fronting method was used instead of modern external beads, maintaining the building’s period look.
Client Involvement and Sustainability
Throughout the renovation, the client was actively involved. They visited Landmark’s workshop, where they saw firsthand the care and craftsmanship that goes into each stage of production. Our workshops offer clients an in-depth understanding of the work being done, typically over a two-hour visit, providing transparency and confidence in our process.
Landmark is committed to sustainability, and this project was no exception. All timber used was sourced sustainably in line with FSC standards. Offcuts were repurposed for small beadings and detailed work, minimizing waste. By manufacturing all timber components in-house, we maintain quality control and reduce environmental impact.
The Restoration Process
In keeping with the council’s request, Landmark undertook extensive repairs to retain the original window frames. Here’s an overview of the process:
Stripping back paint: We started by burning off layers of accumulated paint and freeing sashes that had been painted shut over the years.
Hardwood repairs: Next, we addressed the frame structure. This involved installing a new trenched sill and replacing pulley stiles as part of the restoration process.
Axle pulleys and weight adjustment: The original axle pulleys were no longer fit for purpose. To accommodate the additional weight of double glazing, we added new timber, half-housed into the frame, for structural support.
Minor repairs and finishing: For smaller repairs, we used Repair Care Epoxy Resin. Once these repairs were completed, the frames were sanded smooth, ready for painting.
Painting and sealing: The box frames were hand-painted with two coats of primer and three topcoats, ensuring both a high-quality finish and long-term protection.
Fitting new sashes: Finally, the new sliding sashes were hung using cords and weights, and the windows were draft proofed using methods approved by English Heritage.
Landmark’s Growing Reputation
Thanks to the quality and care demonstrated on this project, Landmark has been added to the Hampstead Garden Suburb Trust’s list of recommended installers. This recognition reflects our ongoing commitment to excellence in restoring and enhancing listed properties while preserving their historical integrity.
Contact Tom at Landmark Windows today for expert advice on period windows and doors for listed buildings.
Landline: 01992761455
Mobile: 07969840306
Web: www.landmarkwindows.co.uk
Email: info@landmarkwindows.co.uk
Email: tom@landmarkwindows.co.uk