Rawlings Street

Double Height Glazed Extension in London

Rawlings Street is a double height glazed extension designed by Anthro Architecture that transforms a dark London terrace into a light-filled contemporary home. The project combines an oversized vertical sliding sash window with a frameless-effect structural glass roof, creating a dramatic glazed volume that introduces daylight deep into both the ground and first-floor living spaces.

IQ Glass engineered and installed the architectural glazing package, using structural glazing and specialist opening systems to maximise daylight while overcoming the spatial constraints typically associated with Victorian and Edwardian terrace properties.

The result is a contemporary rear extension where natural light, transparency and carefully engineered glazing redefine the relationship between the house and its garden.

Products Used

Project Partners

Anthro Architecture

Location

London
Vertical sash windows maintains the widest aperture to London double height glazed extension
Double height 'up and over' structural Invisio glazing by IQ
Double height glass creates an atrium to London double height glazed extension
Light-filled kitchen with structural minimal framed glass by IQ

Double height glazed extension for a London terrace renovation

The primary challenge at Rawlings Street was to bring significantly more daylight into an existing terrace property with limited opportunities for expansion. Rather than relying on conventional rear extension glazing, the design centred around a double-height glazed volume that connects the ground and first floors through a large structural glass façade and rooflight.

At the heart of the design is an oversized vertical sliding sash window that exceeds 4m in height and over 2m in width. This large opening is bonded directly to structural glazing, creating a continuous glazed elevation that visually extends across both levels of the extension.

The combination of the vertical sliding sash window and frameless-effect structural glass roof allows daylight to penetrate deep into the building, creating a bright mezzanine level and transforming previously dark internal spaces.

Oversized sliding sash window for maximum opening width

A key architectural feature of the project is the oversized vertical sliding sash window. The opening measured 2,234mm wide, making conventional sliding or bifold doors less suitable as they would have significantly reduced the clear access opening.

Instead, a vertically sliding sash system was selected to maximise access to the patio while maintaining a minimal glazed appearance. The system uses a concealed pulley-weight mechanism housed within the frame to counterbalance the sash, allowing the oversized glazing panel to operate smoothly despite its scale.

This approach delivered both unrestricted access and maximum daylight while preserving the clean architectural lines of the extension.

Frameless structural glass roof and mezzanine glazing

The extension incorporates a frameless-effect structural glass roof that extends up and over the rear elevation. This structural glazing solution allows daylight to flood both floors of the home while visually connecting the internal spaces with the sky above.

The glazed roof works alongside more than 5 metres of structural glazing spanning the ground and first floor, creating a bright mezzanine arrangement within the reconfigured layout. Glass balustrades were also installed at first-floor level to maintain clear views through the double-height space and maximise the flow of natural light throughout the extension.

Vertical sash window to London terrace property
Light filled atrium is created with double height structural glazing to London contemporary extension

Performance considerations

Performance requirements for this double height glazed extension were driven by the need to maximise daylight while maintaining thermal efficiency and usability within a constrained urban site.

The up-and-over structural glass roof was engineered using a thermally broken structural glazing system, providing the frameless appearance required by the architecture while improving thermal performance. The oversized sliding sash window was selected not only for its appearance but also for its ability to provide a larger clear opening than alternative door systems within the available width.

Installation logistics were also a significant consideration. With no access to the rear elevation, all oversized structural glass elements had to be craned over the existing property. This required careful coordination, specialist lifting equipment and precise installation planning to position the glazing accurately within the completed extension structure.

The result is a light-filled contemporary extension that combines structural glazing, specialist opening systems and architectural detailing to maximise daylight, openness and usable space within a dense urban setting.

Technical details

  • Oversized sliding sash window: minimal framed vertical sliding sash configuration; over 4m high and more than 2m wide; designed to maximise the full 2,234mm opening width; concealed pulley-weight counterbalance system enables smooth manual operation of oversized glazing panels
  • Frameless structural glazing: thermally broken fixing system; 63mm profile depth; max glass thickness 41.5mm; expected Uw 1.1 W/m²K; minimum fixing setback 55mm; profile height 60mm; structure deflection allowance 5mm; used for the double-height glazed elevation and up-and-over roof glazing
  • Structural glass roof: frameless-effect up-and-over rooflight configuration; thermally broken structural glazing detail; delivers daylight to both ground and first-floor spaces while maintaining clear sightlines
  • Double-height glazing: over 5m of structural glazing spanning ground and first-floor levels; creates a light-filled mezzanine space and strengthens visual connections throughout the extension
  • Glass balustrades: frameless glass balustrades used to preserve views and daylight through the mezzanine level; maintaining transparency within the double-height volume
  • Specialist installation: all oversized glass elevations craned into position due to restricted rear access typical of a London terrace property

Structural glazing for double-height home extensions

Rawlings Street demonstrates how structural glazing, oversized sliding sash windows and frameless roof glazing can transform a restricted urban property into a bright and spacious contemporary home.

This approach is particularly suited to architects and specifiers designing double-height extensions, mezzanine spaces and urban renovations where maximising daylight and maintaining visual openness are key project objectives.

To discuss a similar double height glazed extension, contact IQ Glass for technical advice on structural glass roofs, oversized sliding sash windows, frameless glazing systems and specialist installation strategies for constrained urban sites.

Associated Products

a frameless rooflight over an extension in London

Thermally Broken Rooflights

Thermally broken rooflights have insulation between the inner and outer frames, reducing heat loss and preventing condensation, while allowing natural light into a building.
Oversized sliding sash window at Dormers by IQ Glass

Oversized Sliding Sash Window

An oversized sliding sash window typically consists of one or more sashes that slide vertically within a frame. They can provide excellent ventilation and natural light while also being energy-efficient when properly sealed and insulated.

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