Frameless Glass Box Extensions UK | Contemporary Glass Extensions | Room Outside®

Contemporary Glass Extensions UK

Frameless Glass Box Extensions: Minimalist Modern Design

Ultra-slim structural glazing creates a seamless connection between your home and garden. Floor-to-ceiling glass and stunning contemporary aesthetics.

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Call us anytime on 01243 538999 – David our digital assistant will take a few details so the right specialist can follow up personally.

Price From
£40,000
Build Time
12-16 Weeks
Thermal Rating
A++ Rated
Guarantee
10 Years
Frameless glass box extension with structural glazing - Room Outside UK
From £40,000

What is a Glass Box Extension?

A glass box extension represents the pinnacle of contemporary architectural design. Using structural glazing technology, these minimalist extensions create an almost invisible boundary between your living space and garden.

At Room Outside, we specialise in bespoke glass box extensions featuring floor-to-ceiling glass panels, flat structural glass roofs and large-format sliding or pivot doors. Each installation is precision-engineered to create a seamless indoor-outdoor living experience.

Key Benefits

Maximum natural light
Contemporary aesthetic
Seamless indoor-outdoor living
Large-format sliding doors
10-year comprehensive guarantee
Full planning support included
Structural engineering included
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Premium Features

Glass Box Extension Features

Every glass box extension is precision-engineered with premium structural glazing and the latest thermal technology.

Frameless Structural Glazing

Constructed using structural safety glass with structural glass purlins sealed with structural silicone bonding using unique and specialist techniques.

Floor-to-Ceiling Glass

Full-height glazing maximises views and floods your space with natural light.

Sliding & Pivot Doors

Choose from large-format sliding, pivot or bi-fold doors for dramatic openings.

Walk-On Glass Roofs

Optional glass roofs create stunning visual connections between floors.

Door Options

Door & Opening Options

Choose from a range of premium door systems to complete your glass box extension.

Sliding Glass Doors

Up to 6m opening width Ultra-slim profiles Flush floor tracks

Pivot Doors

Up to 3m height Hidden pivot mechanism Dramatic entrance

Bi-Fold Doors

Multiple panel options Full corner opening Low threshold
Expert Answers

Glass Box Extension FAQs UK

Common questions about glass box extension costs, planning and installation in the UK.

A glass box extension is a minimalist architectural addition using structural glazing. It creates an almost invisible boundary between your living space and garden, maximising natural light and views.
A frameless glass box extension typically costs from £40,000 to £100,000+ depending on size, glass specification, and complexity. Room Outside offers premium glass extensions from £40,000 fully installed with building control and 10‑year guarantee.
Many glass extensions fall under Permitted Development Rights, but restrictions apply in conservation areas and for listed buildings. Room Outside provides full planning guidance with every project.
Yes. Our glass box extensions feature New Generation Glass technology with advanced thermal breaks and low‑e coatings, achieving A++ energy ratings. They keep you warm in winter and cool in summer.
A typical glass box extension takes 12‑16 weeks from initial consultation to completion, including design, structural engineering, foundations, installation and finishing.

Get Your Free Glass Extension Quote

Book a free home design consultation with our specialist team. We’ll discuss your vision, assess structural requirements and provide a detailed quotation.

Talk to a Service Specialist Request Free Brochure

Call us anytime on 01243 538999 – David our digital assistant will take a few details so the right specialist can follow up personally.