Exterior Plas was founded in 1988 by Andy Sheen, and most of the windows we install are built on the same site as our showroom in Thornwood, Epping. We've manufactured our own frames from the start, so this guide follows a single job to show how windows are made in house, from the first survey to the day our fitters finish. It's written for homeowners, but the councils, housing associations and schools we work with across London and the South East get exactly the same process.
Key takeaways
* We've manufactured and installed windows since 1988, and our Thornwood factory covers around 15,000 sq ft and uses CNC machinery.
* We fabricate REHAU systems for our uPVC windows.
* Every job follows the same path: survey, quote, manufacture and installation.
* You can visit the showroom at the same Thornwood address and look at finished windows and doors there.
* Repairs usually suit reactive maintenance better than a full replacement.
Why we make our windows in house
Making our own windows keeps the whole job under our control, from the survey notes to the fitting date. That's the short answer.
When frames come from an outside fabricator, every query about a size or a finish has to pass through another company before anyone in our team can act on it, and that adds steps. Here, the factory sits beside our head office, so a surveyor's notes go straight to the people who'll prepare the frames.
It's also why made to measure work suits us, because every opening is slightly different. A Victorian terrace, a 1960s school and a new build flat won't share the same sizes, and we'd rather build to the real opening than force a standard frame into a gap it doesn't fit.
What happens at the survey
The survey is where your windows are really designed. Every frame is built from the measurements taken on site, and nothing goes to the factory until those sizes are confirmed.
Our surveyor measures each opening and checks the existing frames and the brickwork around them before moving on to the specification. They'll go through style, colour, opening type and glazing with you, and it helps to tell them how you use each room.
Once you're happy, we'll prepare a quote, and it's free. We don't publish standard lead times because they depend on the order size, the material and what's already in production, so you'll get a realistic date for your own job instead.
How windows are made in house, step by step
Once an order is confirmed, the survey sizes go into production at our Thornwood factory, and the table below shows the route it takes.
| Stage | What happens |
|—|—|
| Survey sizes into production | Confirmed measurements become the order the factory builds to. |
| CNC cutting and machining | Our CNC machinery cuts and machines the profiles on site. |
| Fabrication | We fabricate the frames in house, including REHAU systems for uPVC. |
| Ready for fitting | Finished windows leave the factory for installation by our team. |
If you're ordering aluminium or timber windows, ask at the survey how your order will be made and we'll explain it in plain terms.
For uPVC, we fabricate REHAU systems into finished windows in Thornwood. REHAU is an international polymer company whose range includes window profile systems, and there's more on our uPVC windows page.
From factory to fitting
Our fitters work from the same survey record the factory used to build your frames, and that shared record is the real benefit of keeping the whole job in house.
On the day, the old frames come out and the new ones are fixed in place and sealed. Replacement windows in England have to meet Building Regulations, and schemes such as FENSA let registered installers self certify that work. Check membership before you sign, and we're happy to answer that question when we quote.
Can you visit the showroom?
Yes. The showroom is at Weald Hall Lane, Thornwood, Epping, Essex CM16 6NR, on the same site as our head office and factory, and you can look at finished windows and doors there.
It's best to call ahead on 01992 578 903 between 9am and 5pm, Monday to Friday, or email enquiries@exteriorplas.com. You can also use our contact page to ask for a free quote or book a survey, and the factory page listed in the sources below explains more about the manufacturing site itself.
When this is not the right choice for your window
A full manufacture and install job isn't the right choice if only part of a window has failed, which is what our reactive maintenance department is for.
The department started in 2007, growing out of the manufacturing and installing work we'd done since 1988, and our reactive maintenance page has the details. If a sealed unit has misted, a handle has snapped or a hinge has dropped, the frame itself may be fine, and a repair is usually less disruptive than a new window.
Location matters too. We only cover London, Essex and the South East, so properties further afield will be better served by a local firm.
FAQs
How long does it take to make a window in house?
It depends on the order and the factory's workload at the time, so there's no standard figure. We'll confirm a realistic date for your job when we quote.
Are your windows made to measure?
Yes. Each frame is built from your survey sizes for that specific opening.
Do you use REHAU systems?
We fabricate REHAU systems for our uPVC windows. If you'd like to know which profile suits your property, ask at the survey or call the office.
Do you work with councils and housing associations?
Historically, that's where much of our expertise has been, alongside the educational sector, although we also take on commercial and domestic projects and deal with the trade. If you're unsure whether your project fits, call the office and we'll talk it through.
Sources
* Reactive maintenance, Exterior Plas
* REHAU UK
* FENSA