hup! Building System
hup! Extensions — The Smarter Way to Extend Your Home
If you’ve been putting off a home extension because of the cost, the mess, or the months of disruption, the hup! Building System changes that. Window Mart are approved installers of hup! across Horsham, Crawley and West Sussex, and we can have your new space watertight in days and complete in weeks, not months.
Faster to build, warmer to live in, and better for the planet, hup! is the future of home extensions.
🟢 Built in weeks, not months
🟢 Five times more energy efficient
🟢 Designed and manufactured in the UK
What Is the hup! Building System?
hup! is a modern modular building system developed by Ultraframe — the UK’s leading conservatory and extension manufacturer with over 30 years of experience. Instead of traditional brickwork, hup! uses pre-fabricated insulated wall panels that are delivered to your home and assembled on-site by our expert team.
The result is a fully insulated, Building Regulation-compliant extension that’s faster to build, warmer to live in, and generates 60% less carbon than a traditional brick build.
🟢 Fast – Built in weeks, not months
🟢 Energy Efficient – Five times more thermally efficient than the average UK home
🟢 Eco-Friendly – 60% less carbon than traditional brick builds
🟢 Flexible Design – Works with any wall finishes, windows, and doors
🟢 Hassle-Free – One team, one project, no architects needed
🟢 Trusted Technology – Manufactured by Ultraframe, BBA approved
Contact us Today for your free quotation!
Why Choose hup! Over a Traditional Extension?
Traditional brick extensions take months, require multiple trades, and often run over budget. hup! is designed to solve all three problems.
The wall panels are slimmer than standard brickwork, around 215mm versus 300–350mm for brick, which means you actually gain more usable internal floor space without increasing your external footprint. The walls achieve U-values as low as 0.17 W/m²K, making them five times more thermally efficient than the average UK home.
And because hup! is manufactured off-site, delivered flat-packed and assembled by one team, there’s less waste, less noise, and far less disruption to your daily life.
What Can You Use hup! For?
hup! is flexible enough to work across a wide range of projects:
Conservatory conversion — if you have an old conservatory that’s too hot in summer and too cold in winter, hup! can transform it into a fully habitable room with solid insulated walls and a proper roof. It works on most existing conservatory bases, so no need to dig up your garden.
New home extension — kitchen extension, open-plan family room, home office, garden room. hup! handles it all, with any combination of wall finishes, windows, doors and roof options.
Orangery or garden room — hup! pairs beautifully with lantern roofs, bi-fold doors and large glazed panels for a high-end finish that looks like it cost twice as much.
Ready to Build the Better Way?
Get in touch to explore your hup! project with the Window-Mart team.
We’ll guide you through design ideas, pricing, and timelines, with no obligation.
Get a Quote
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Download the Brochure
“hup! is an absolute game changer” – Laura Jane Clark, Leading Architect & Star of BBC’s Your Home Made Perfect
Frequently Asked Questions
Yes — one of the biggest advantages of hup! is that it’s lightweight enough to be built on most existing conservatory bases. This saves significant time and cost compared to starting from scratch, and means you don’t have to excavate your garden.
Most hup! projects are watertight within days of the panels going up, with the full build typically complete within a few weeks. This compares to three to six months for a traditional brick extension of similar size.
Significantly more. hup! walls achieve U-values as low as 0.17 W/m²K and are five times more thermally efficient than the average UK home. A hup! build also produces around 60% less carbon during construction compared to traditional brickwork.
Yes — like any extension, a hup! build will require Building Regulations approval. All hup! components are Building Regulation compliant and BBA approved, which makes the process straightforward. Window Mart can advise you on the approval process as part of your project.
Home offices, family rooms, kitchen extensions, hobby spaces, hup! adapts to your needs.
hup! is compatible with flat roofs, glass roofs, hybrid roofs and tiled roofs, including lantern and rooflight options. Your choice of roof will affect both the look and the price of the project — we’ll talk you through the options when you request a quote.
Most hup! extensions fall within Permitted Development rights, meaning you won’t need formal planning permission. However, this depends on the size, position and your property type. If you’re in a conservation area or your property is listed, different rules may apply. Window Mart can advise you at the quoting stage.
We install hup! extensions across Horsham, Crawley, Worthing, Chichester, Eastbourne and the wider West Sussex area. Get in touch to discuss your project.
Costs can start from around £15,000 for a conservatory conversion and £30,000+ for a new single-storey extension, depending on size, spec and roof choice. Contact us for a free no-obligation quote, with hup! the price you’re quoted is the price you pay.
Would you like to see our range of brochures?
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Why Choose Us?
Price Match Guarantee
Our Price Match Guarantee means we will match any like for like quotation with the same features, specifications and warranties.
All Seasons Living
Combine the light and airy feel of a conservatory, yet with the solid, tiled roof, and energy efficiency of an extension.
Over 50 Front Doors
We have a wide range of over 50 white, coloured & woodgrained Front PVCu and Composite Doors to choose from. Starting from just £645.
FREE Quotation
Whatever your requirements, please contact us now for a comprehensive FREE no obligation quotation, or just for some friendly advice.
Best Price Promise GUARANTEE*
*Provide us with a Like for Like quotation with the same features, specifications and warranties from a comparable company,and we will match the PRICE.
Call us on Now 01403 711 936
Email: info@window-mart.co.uk
Do you need a quote?
About
Established in 1998, Window Mart have gone from strength to strength culminating in the opening of our new show complex at Old Barn Garden Centre near Horsham. All Window Mart staff are employed by the company and drive fully equipped company vehicles. We have our own building team for groundwork and brickwork. In our showroom an extensive range of conservatories, doors and windows can be viewed. Excellence is our commitment and we are here to make sure you get the very best in service and quality.
hup! is a registered trademark of Ultraframe (UK) Ltd.
Contact Us
01403 711 936
info@window-mart.co.uk
Show Complex
Old Barn Garden Centre,
Worthing Road, Dial Post,
Horsham, West Sussex,
RH13 8NR
Opening times:
Mon -Sat: 10am – 4pm
Sunday: 11.30am – 3.30pm