Glass Extensions

Structural Glass Extensions: Architecture Without Boundaries

A glass extension is more than an addition to your home — it is an architectural statement. Structural glass walls, frameless bonded corners and minimally framed glass roofs combine to create living spaces that dissolve the boundary between interior and exterior, flooding your home with natural light while providing the thermal performance and weatherproofing that year-round habitation demands.

Every glass extension we design is a bespoke, architect-specified investment. We work directly with your architect or design team — or can recommend architectural practices experienced in structural glazing — to develop a design that responds to your site, your lifestyle and your aesthetic vision. From initial consultation through AutoCAD detailed drawings to final installation, our process is engineered for precision and transparency.

Our structural glass extensions range from single-storey rear additions opening onto Surrey gardens to double-height glazed volumes for contemporary new builds across London and the South East. We combine frameless structural glass technology with thermally broken aluminium framing systems to achieve the optimal balance of transparency, thermal performance and structural integrity for every project.

Full structural glass walls with bonded glass corners
Frameless or minimal-frame glass roofs
Thermally broken aluminium framing (where required)
Double and triple glazed units from 1.0 W/m²K
Compatible with underfloor heating systems
Integrated drainage and weathering details
AutoCAD drawings, structural calculations and full design service

Glass extensions are among the most transformative home improvements available, and are consistently among the highest-value additions in terms of both lifestyle quality and property value. In the premium residential markets of Surrey, West London and the Home Counties — from Weybridge to Wimbledon, Cobham to Chelsea — a well-designed glass extension can redefine how you live in your home.

Modern house with large glass windows and wooden accents, set in a lush green garden under a blue sk.

Your Investment: What to Expect

Structural glass extensions are a bespoke, architect-specified investment. Unlike standard conservatories or off-the-shelf garden rooms, every element is designed, engineered and fabricated to your specific project. Costs depend on the size and complexity of the design, the glass specification, structural steelwork requirements, site access and ground conditions.

We provide an initial consultation — typically at your property or via your architect's drawings — to understand your project requirements and establish an indicative budget range. This consultation is without obligation and ensures you have realistic cost expectations before committing to detailed design work. Following approval to proceed, we produce full AutoCAD detailed drawings and a comprehensive quotation covering all materials, fabrication and installation.

Our quotations include the full design service, all glass and framing materials, structural silicone bonding, weathering details and professional installation by our specialist team. We do not provide itemised cost breakdowns that invite cherry-picking of components — structural glass is an integrated system where every element depends on every other.

Technical Specifications
Colours & Finishes

Technical Specifications

Parameter	Specification
Structural Glass Walls	Toughened laminated glass, 21.52mm minimum
Glass Roof Panels	Laminated safety glass, self-cleaning coating available
Corner Joints	Structural silicone bonded (frameless) or minimal aluminium
Glazing Units	Double glazed (28–44mm) or triple glazed (36–54mm)
U-Value (Walls)	From 1.0 W/m²K (double glazed, argon filled)
U-Value (Roof)	From 1.0 W/m²K with solar control coating
Structural Support	Concealed steel frame, glass fins or hybrid structure
Drainage	Integrated concealed gutter and downpipe system
Flooring Integration	Level threshold details for seamless inside/outside transition
Building Regulations	Full Part L, Part K, Part B compliance

Configuration Options

Extension Types

Single-Storey Rear Extension — The most common configuration: a glass box addition to the rear of the property, opening onto the garden. Typically 3m–6m deep with full-width glazing.
Side Return Extension — Glazing over a side passage or return to create a light-filled kitchen-diner. Glass roof with minimal framing maximises overhead light.
Wraparound Extension — Combining rear and side extensions with frameless corner glazing. Creates an L-shaped or U-shaped glass addition.
Double-Height Glazed Volume — Floor-to-ceiling structural glass spanning two storeys. Creates a dramatic atrium or gallery space.
Basement Lightwell — Structural glass enclosure over a basement lightwell, with walk-on glass floor panels at garden level.

Roof Options

Flat Glass Roof — Minimal-frame flat glass roof with integrated drainage. Clean, contemporary aesthetic.
Pitched Glass Roof — Traditional pitched roof form in structural glass. Maximises headroom and volume.
Glass Roof with Lantern — Flat glass roof with a raised lantern section for additional height and ventilation.

Glass Specifications

Glass Specifications for Extensions

Application	Glass Type	Performance
Vertical Glazing (Walls)	Double or triple glazed, Low-E, argon filled	U-value from 1.0 W/m²K
Overhead Glazing (Roof)	Laminated inner pane (safety requirement)	U-value from 1.0 W/m²K
South-Facing Panels	Solar control coating (e.g. Guardian SunGuard)	g-value 0.25–0.40 to reduce solar gain
High-Level Glazing	Self-cleaning coating (Pilkington Activ)	Reduces maintenance on inaccessible panels
Privacy Panels	Switchable smart glass (clear to opaque)	Instant privacy at the touch of a button
Corner Joints	Low-iron (Optiwhite) for colour-matched corners	Eliminates green tint at bonded corners

Glass Specification

All glass extensions are supplied with high-performance double-glazed or laminated sealed units as standard. Upgrade options include:

Thermal performance — Warm-edge spacer bars, argon or krypton gas fill, triple glazing available
Solar control — Low solar-gain coatings for south-facing applications
Security — Laminated inner panes, PAS 24 tested units available
Acoustic — Acoustic laminated glass for road-facing or party-wall applications
Self-cleaning — Photocatalytic coating for hard-to-reach overhead glazing

Glass Options

All our glass extensions are available with a choice of high-performance glazing to suit your project requirements:

Double-glazed sealed units — standard specification for thermal efficiency
Triple-glazed units — enhanced thermal and acoustic performance
Acoustic laminated glass — for noise reduction in urban and roadside locations
Solar control glass — reduces heat gain and glare while maintaining natural light

We specify the optimal glass configuration for each project based on thermal performance, acoustic requirements and Building Regulations compliance.

Colours & Finishes

Powder Coat Colours

All aluminium frame and fixing components are powder coated to order. Standard colours available from stock:

Anthracite Grey — RAL 7016 (most popular for contemporary projects)
Jet Black — RAL 9005
Pure White — RAL 9010
Traffic White — RAL 9016

Any RAL colour is available to special order, typically adding 2–3 weeks to lead time. For heritage projects, BS 4800 and NCS colours can also be matched.

Anodised Finishes

Silver Anodised — Natural aluminium appearance with enhanced corrosion resistance
Black Anodised — Deep, consistent black finish with a harder surface than powder coat
Bronze Anodised — Warm tone suited to traditional and heritage contexts

Structural glass framing is typically specified in minimal finishes — mill-finish anodised, satin black or anthracite grey — to keep the focus on the glass itself.

Frequently Asked Questions

How much does a glass extension cost?

Glass extensions are a bespoke, architect-specified investment. Costs vary significantly based on size, design complexity, glass specification, structural steelwork requirements and site conditions. We provide an initial consultation to understand your project and establish an indicative budget range before committing to detailed design work. Contact us with your architect's drawings or brief for an accurate assessment.

Do I need planning permission for a glass extension?

Many single-storey rear glass extensions fall within permitted development rights, meaning planning permission is not required — subject to size, height and boundary constraints. Extensions in conservation areas, on listed buildings or exceeding permitted development limits will require planning permission. We can advise on the likely planning requirements during your initial consultation.

How long does a glass extension project take from start to finish?

A typical glass extension project takes 12–20 weeks from initial consultation to completion, depending on complexity. This includes design and AutoCAD drawing production (3–4 weeks), structural calculations and approvals (2–3 weeks), glass fabrication (4–6 weeks) and installation (2–4 weeks). Larger or more complex projects may take longer.

Will a glass extension be too hot in summer or too cold in winter?

Modern glass extensions are engineered for year-round comfort. We specify solar control glass on south and west-facing panels to reduce summer heat gain, and high-performance Low-E coatings with argon gas filling to minimise winter heat loss. Combined with underfloor heating and appropriate ventilation, a well-designed glass extension maintains comfortable temperatures throughout the year.

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