The retrofit of The Harrison in Shoreditch, formerly Curtain House, has positioned Associated Steel Window Services (ASWS) at the centre of one of London’s most detailed heritage fenestration programmes. The Grade II listed warehouse has been converted by Red Construction into 40,000 sq. ft. of workspace, targeting BREEAM Excellent and EPC ‘A’ ratings, with window performance forming a core compliance element.

ASWS delivered four distinct work packages: refurbishment of existing timber windows, selective timber replacement, full restoration of historic steel Mid Universal section frames, and fabrication of new steel windows for the reconfigured rear entrance. Using a single contractor prevented finish discrepancies and provided the project team with unified glazing specification control and sequencing.

Once scaffold access was gained, sub-frame decay proved greater than survey projections. Twelve timber windows required full sill replacement in kiln-dried hardwood, with spliced components milled to match original 19th-century profiles. In multiple locations, steel frames above could not be removed, necessitating insertion of new sub-frame material in three slim pre-milled pieces, assembled internally to avoid disturbing fixed metalwork.

The now-obsolete Mid Universal steel profiles were replicated using plate-built substitutes, cut and welded on site to exact match tolerances. Original ironmongery, including stays, pins and locking assemblies, was demounted, mechanically stripped, re-polished and lacquer sealed, rather than re-specified.

Across the building, ASWS reglazed nearly 350 panes. Select bays received slimline 4-4-4 IGUs with 7 mm warm-edge spacers, improving U-values from around 6.4 W/m²K (single glazing) to 2.6 W/m²K, with spacer bars concealed below upstands to retain original sightlines. Traditional putty glazing was reinstated on heritage faces, requiring coordinated curing windows with decorators.

Twelve large internal sliding steel doors were refurbished but fixed shut due to operational load risks. Party wall delays meant newly fabricated steel units were stored off-site to prevent façade scheduling conflict.

The completed works deliver both accurate period detailing and measurable thermal uplift, critical in achieving The Harrison’s energy targets.