My friend Sarah was thrilled about the idea of a glass extension of her Victorian terrace. a few months back.
“It’ll be amazing,” she said as her first remark. Natural light with views of the garden, the entire package.
But three months later, a reality hit her, when she was facing condensation problems with a £12,000 budget increase.
These are the things she wished, she’d known beforehand.
1. Budget Reality – Beyond Just Glass
Let’s talk money first.
Most homeowners think a glass extension is like a regular extension, but shinier. Well, it’s not.
Modern glass extensions typically cost thousands for the glazing alone. And that’s even without groundwork, structural engineering, or the actual installation.
Why is it so expensive?
One word, the specialized materials. You’re not buying standard windows. Glass extensions need strict measurement, and premium material that will carry huge glass panels.
The installation and relocation of oversized glass panels occasionally involve the use of cranes. A single wrong move and you’re starting over.
You need professionals. There goes a slice of the pie to each architect, structural engineer, and specialist glazing contractor.
At Atelier BDB, we are a one-stop shop. Because, we deal with everything from initial consultation to all the way to final installation. Our team has four and a half decades of combined experience that translates into fewer surprises and fewer expensive mistakes.
What Drives the Cost Up:
- Extension size: The bigger the extension, the more materials required and the longer time it takes to install.
- Glass specification: Triple glazing with solar control is an expensive choice as compare to regular double glazing.
- Frame material: Steel frames cost more than aluminium but offer slimmer sightlines
- Opening options: Bifold doors and sliding options will increase the overall cost.
- Complexity of the site: When access is not easy or the installations are located on the third floor, the cost of labour is higher.
2. Real Layout Decisions That Actually Matter
Your glass extension layout isn’t just about where to stick the sofa.
It’s about how you’ll use the space year-round.
I’ve seen homeowners create beautiful glass rooms that become unusable saunas in summer or freezing boxes in winter. That’s poor planning, not poor glass.
- Think about orientation. South-facing extensions despite being flooded with light can overheat easily. While, North-facing spaces stay cooler that might require more heating during winter. Solar control coatings and heated glass options can cost more upfront. But they will ensure your space remains comfortable throughout the year.
- Consider existing room flow. Instead of feeling like an afterthought, a custom glass extension design will blend in seamlessly with your house. Where will people naturally walk? Where does furniture make sense?
- Door placement is critical. Sliding doors take up less swing space than bi-folds, but don’t open as wide. At Atelier, our engineered portal frame system can give you the widest door openings you can imagine.
- Privacy versus views. Glass walls are stunning until your neighbours can watch you eat breakfast. Strategic positioning, screening plants, or tinted glass sections can resolve this without sacrificing light.
Space Planning Essentials:
Plan for electrical outlets now. Running power later means exposed conduits or expensive retrofitting.
Think about heating and cooling from day one. Underfloor heating is great for glass conservatory extensions because it doesn’t block views.
Leave room for blinds or shade. On hot days, even the best solar control glass needs help sometimes.
3. Thermal Efficiency – The Make or Break Factor
Here’s the uncomfortable truth about glass extensions.
Get the thermal performance wrong and you’ve just built an expensive greenhouse.
To counter that there is a new type of insulated glazing available that employs the Low-E (low-emissivity) coating. This reflects heat back into your room in winter and blocks out too much solar heat in summer. It also makes contemporary glass extensions actually usable, unlike those old conservatories that felt like ovens in July and fridges in January.
U-values matter. This determines the amount of heat that gets out of your glass. Lower is better. Single glazing is not well thermally insulated, with U-values of about 5.0. This is reduced to 1.6 to 3.0 with double glazing and 0.8 to 1.2 with triple glazing.
Building regulations in the UK now require extensions to meet minimum thermal efficiency standards. Your glass needs to perform as well as a solid wall would.
At Atelier BDB, we’ve developed a unique conservatory and glass extension system that delivers thermal efficiency performance, solar control glass, and building regulation compliance as standard. Our systems use premium materials engineered specifically for the UK climate.
Gas Fills and Glazing Options
The air between the glass panes is not air anymore.
The most common gas used is argon gas since it is denser than air and therefore minimizes the transmission of heat. Krypton also works even better, but is more expensive.
Frame materials affect thermal performance, too. Aluminium conducts heat easily, which is why quality systems like ours use thermal breaks. These insulating barriers inside the frame prevent cold transferring from outside to inside.
The result? A structural glass extension that London homeowners actually want to use in February.
4. Planning Permission and Building Regulations
Most glass extensions don’t need planning permission.
But “most” isn’t “all,” and getting this wrong is expensive.
Glass extensions normally fall within the category of permitted development. For instance, you do not require planning permission as long as your extension does not exceed some of the statutory limits. That is more than half your garden, taller than your existing roof, or longer than 3-4 meters at the back of your property.
But it gets complicated in case of conservation areas, listed buildings, or Article 4 Direction zones. In such instances, you require full permission for planning.
Here’s the good news. Planning officers often prefer glass extension London projects over brick extensions in conservation areas. Why? A frameless glass extension clearly distinguishes old from new. It doesn’t try to fake historical architecture.
We’ve handled numerous planning applications at Atelier BDB. One client’s Victorian terrace in Hackney sat in a conservation area. Their previous brick extension application was rejected. Our glass extension design sailed through because it enhanced rather than competed with the original architecture.
5. Build Timeline: What to Actually Expect
Most contractors will tell you 6-8 weeks. Sometimes that happens. Often it doesn’t.
Here’s why timelines slip and how to avoid surprises.
A typical Time estimate can range from 10 to 16 weeks on simple projects, 18 to 24 weeks with the need to obtain planning permission.
Ground conditions can cause more delays than anything else. If your site needs significant excavation, damp-proofing, or underpinning, add weeks. Weather matters too. Concrete needs specific conditions to cure. Heavy rain during groundwork adds days.
Once fabrication is completed, installation is surprisingly fast. Our teams typically complete installation in under a week. Everything arrives pre-fabricated and engineered to millimetre precision.
At Atelier BDB, our project manager leads from technical fabrication through installation. When the man who made your extension is the one who is putting it on, details do not get lost.
The Bottom Line
Glass extensions transform how you live in your home.
Dark becomes light. Cramped becomes spacious. Disconnected becomes seamless.
At Atelier BDB, we’ve delivered exceptional results for over 45 years. We handle every aspect from initial consultation through survey, planning permissions, structural calculation, and building control to final completion.
Ready to explore what’s possible? Get in touch with our team. We will come to your house, talk about your objectives, and demonstrate how a custom-made glass extension can help to make your living room better.
FAQs:
The duration of a normal glass extension construction?
It is different according to the size, site access, and planning needs. A survey through design, approvals, and construction should take several months.
What is required in the planning permission for a glass extension in London?
It will require the status of your property (e.g., conservation area), the size of the extension, and the effect on neighbours. An expert builder is able to deal with the filing and appeals on your behalf.
Will it be too hot/cold in summer or winter with a glass extension?
Not when it is designed and specified right. Having enhanced glass, an insulated frame, and solar control features, you are able to have a place that is utilised throughout the year.
Can I personalise the frame colour and size of doors/windows?
Yes. Our bespoke design approach offers powder-coated aluminium frames in a variety of colours as well as tailor-made sizes to fit your house indoors/sliding systems.
Would a custom-made glass extension enhance my house?
It does, yes, most frequently, when it is well constructed and planned. It is an addition of usable space, light, and high-end looks. But worth lies in quality, specification, and union with the house.
