Project 538
38 Grosvenor Square
Mayfair · Grade II* listed
The sensitive environmental upgrading of a Grade II* listed building overlooking Grosvenor Square.
01Thermal upgrade of lead-covered roofs
02Secondary glazing to historic sashes
03Restoration of the roof lantern
38 Grosvenor Square forms part of one of London’s most distinguished historic squares, within the Mayfair Conservation Area.
The project was a carefully considered programme of environmental improvements and conservation repairs, retaining historic fabric while improving thermal performance and long-term durability.
The roofs
Insulating lead without trapping moisture
The principal element of the works was the reconstruction and thermal upgrading of the traditional lead-covered pitched roofs. The design needed detailed consideration of insulation, vapour control, ventilation and moisture movement, so that it would work with the existing historic construction.
The new build-up places insulation above the structural deck, with a continuous vapour control layer and cross-ventilation beneath the lead. At junctions, parapets and restricted roof voids, the balance between insulation thickness and ventilation was critical to preventing condensation and protecting the timber structure below.
The windows
Warmer and quieter, unchanged outside
The historic timber sash windows were retained and upgraded with discreet, slimline Selectaglaze secondary glazing. This improved thermal and acoustic performance while preserving the original joinery, glazing proportions and character of the principal elevations.
The works also included restoring and refitting an existing roof lantern, with detailed conservation oversight throughout construction.
The approach prioritised minimum intervention and the retention of significant fabric. It shows how the environmental performance of an important historic building can be improved through technically informed, conservation-led design, without compromising its architectural significance.
Your project
Improving the performance of a listed building?
Tell us about your property and what you hope to achieve. We respond personally, usually within one working day.