Alitherm 400 Doors

Alitherm 400 doors combine clean, modern design with advanced performance and robust security. Designed for everyday use and long-term durability in any home, these tried-and-tested aluminium doors are ideal for both front and back doors, as well as French doors or doors with side panels setups for wider openings. We fit these reliable doors as replacements for old patio doors or in new homes and extensions.

With sleek styling and a choice of single or double door formats, the Alitherm 400 system is suitable for both traditional and contemporary homes. It pairs perfectly with Alitherm windows for a consistent look and delivers excellent energy efficiency, low maintenance, and always-reliable operation.

alitherm residential doors in a new build house beside matching window

Suitable for front, back, and French doors with open-in or open-out designs
U-values as low as 1.1 W/m²K with triple glazing
Multi-point locking with PAS 24:2016 certification and 3-star cylinder
Matches with Alitherm 400 windows

Every Alitherm door is made to order and installed by our trained installers with precision and care for your home. Your new doors are designed to provide solutions for both narrow and wide openings with door sizes up to 2400mm tall and 1100mm wide. Whether you’re replacing an existing door or designing a new extension needed quality, secure and reliable garden doors, Alitherm 400 doors offer the flexibility and durability to suit your needs.

Choose from four stocked finishes or specify any RAL colour for a fully bespoke appearance. Hardware options include high-quality handles, letterplates, and secure hinges – all independently tested for performance and durability. The system is designed to resist wind, water ingress, and forced entry, making it a strong choice for exposed or coastal properties.

At LB Window Systems, we’ve built a reputation for delivering high-quality uPVC and aluminium doors with personal service and expert installation. We work with you to choose the right door style, colour, and glazing, and every Alitherm door we fit is fully guaranteed and installed to the highest standards. If you’re looking for a reliable and stylish aluminium door system, talk to our team today.

Paul Hutton

16:48 03 Feb 26

From day one Gemma and Leigh were superb! Leigh really knows his product and his knowledge and awareness of what we wanted showed from the initial quoting point right the way through to installation and after too. Gemma provides excellent customer service, a great point of contact and kept is the loop throughout on timings. Delighted with the quality of the windows, doors and skylight we had installed and the service throughout. LB Window Systems are a local company proving that trusting and supporting local businesses is best way to do things! Keep up the great work guys!

Izzy Bly

12:37 31 Jan 26

Great service from start to finish. Communicated with us throughout the process, and the final result was fantastic! Would highly recommend.

Shaylene Perry

09:06 26 Jan 26

We had an Origin garage door installed by LB Window System Ltd and couldn’t be happier with the experience. The team were professional, friendly, and communicated clearly throughout the process. When an unexpected issue arose on the day, they went out of their way to make sure the door was fitted properly, which we were extremely grateful for. Excellent service from start to finish — we would highly recommend LB Window System Ltd to anyone.

Rich Coles

22:09 21 Jan 26

Delighted with LB Window Systems from start to finish, very highly recommended. Excellent comunication from the start, very proactive and very personable. We only needed one window installing to match others in our property, but this meant cutting a hole and removing a chimney breast, so much more of a contruction job than a window, and we half expected this to be too small a job for them. Couldn’t be more delighted with the end result, and Mark Taplin, who did the building work was also fantastic. I immediately felt at ease meeting Leigh and Mark and knew we had very trustworthy people we could rely upon to do a great job – and we weren’t disappointed. And Gemma all along excellently managing the communication. Thank you!

Derek Langston

09:59 05 Nov 25

Excellent service good door installed in good time would recommend

Gavin Bowen

18:07 13 Oct 25

Leigh, Gemma and the team did a fantastic job replacing 8 of our windows. Great communications all the way through, turned up when expected, super efficient work and above all they are a really nice and friendly team. Would definitely recommend.

b Mcg

12:33 07 Oct 25

Fantastic quality and the service was excellent. Would definitely recommend.

Alexandra Bruzas

17:05 14 Sep 25

Excellent service from start to finish for fitting bifolds. Good communication, polite and courteous. Installation trickier than initially thought but were able to resolve as well as meet timescale and budget.

Liz Briggs

12:50 11 Sep 25

Fantastic work and great people to deal with, helpful and upfront about the whole process

Kristina Hedley

07:23 20 Aug 24

Beautiful windows, brilliant service and all at a fair price. Leigh & Gemma were fantastic from start to finish. Living in an old property we were skeptical about moving away from wood but the upkeep was too much, so decided to move to an alternative. Leigh knew exactly what product to use and install was perfect. Clean & tidy and finished to a very high standard, we think you’ll agree that they look sunning and it’s very difficult to tell that they arnt wood!

stephen griffiths

17:33 14 Aug 22

Hi had really great service from LB window systems . I had been recommended by my neighbour who had used them over a number of years. I had 12 windows back and front doors fitted and I must say had a 100% positive experience. Leigh, Gemma and everyone I had contact with over the order and fitment process where friendly professional and kept me informed every step of the way. I did have a slight problem with one window mechanism which resulted in another visit. again this was dealt with swiftly and with no drama. I have already recommended LB to friends and family

Sarah Large

08:39 30 Jul 22

Leigh and his team replaced our front and back door, and installed a bifold and full length window. The workmanship is great, the products are good quality and they were friendly, punctual and tidy. We wouldn’t hesitate to recommend them.

Sam Mardle

11:25 21 Jul 22

Great service from start to finish – had all windows replaced, as well as bifold doors and a new front door installed. All look fantastic.

Lewis 621

11:19 22 Jun 22

Recently had all the windows on our house done by LB Window systems and the difference is just incredible! The house looks so much better, service provided by Leigh, Gemma and the team was brilliant, from quotes to the work being carried out in a clean and professional manner. Can’t recommend this company enough, thank you again!

Nicola Shepherd

19:14 28 Apr 22

This is the second time we have used LB Window Systems, having used them last year to replace windows and door on a garden office and been very pleased with the results. This time it was to replace the front door, windows to the front of the house and patio doors at the rear. Leigh and Gemma were very helpful and responsive from the outset, pulling together numerous iterations on quotes to help us get exactly what we wanted within our budget. Five star from start to finish including the results and service. We’ll be using them again when we finally get around to doing the rest of the windows and cannot recommend them highly enough.

S Parky

18:27 17 Mar 22

Absolutely excellent! If I could give a ten star review, I would! (To anyone with any experience of builders/construction etc you’ll appreciate what a rarity that is!!) Leigh has just replaced all the windows on the front of our house and fitted a new front door and we couldn’t be happier. Gemma was fantastic at keeping us up to date on the progress of the job, from organising the initial quote to delivery & installation. Leigh was absolutely brilliant, a proper grafter! Arrived on time every day he was with us and got all of our windows and doors fitted PERFECTLY. His work is so neat we have virtually no making good to do at all. Everything looks fantastic, the impact of outside noise and warmth of our home was instantly improved! The price quoted was very fair and competitive, we would not hesitate to recommend LB window Systems Ltd to anyone. Brilliant. Thank you Leigh & Gemma!

C G

18:18 20 Mar 21

Service was brilliant; Leigh turned up when expected for the quote and Gemma was excellent at providing information throughout, from quote through to updates on delivery and installation. In the day, the installation went brilliantly, even though on of the windows was more difficult due to the previous window being fitted badly. Leigh talked me through everything they were doing and even repaired all the blown plaster caused by the previous window. New windows look fabulous and I’m so so pleased with noise reduction of the road – glad I took Leigh’s advice!

Rebecca Cullum

12:36 03 Nov 20

I would highly recommend Leigh and his team. They recently replaced all of my windows and doors and installed bi-folds at the back of my house. They provided an excellent service with great communication. They were on time, unbelievably efficient and totally professional.

The workmanship, attention to detail and overall finish provided by Leigh and the whole team is absolutely first in class. I could not be any happier with the overall experience as well as the end result. I would have no qualms whatsoever in recommending LB Window Systems, in fact if you can manage to secure them to install for you, you are incredibly lucky!

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Thursday	08:30 – 18:00
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Saturday	09:00 – 15:00

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