More light. Bigger feel. Frontage that looks the part.
Bay and bow windows open up a room with extra daylight and a wider view. They add presence to the front elevation and make lounges and dining rooms feel larger without changing the footprint. We make and fit bay and bow windows across Grantham, Stamford, Sleaford, Newark, Bourne, Melton Mowbray and nearby villages.
Brighter rooms
Angled or curved frames pull in more natural light.
Sense of space
Projection creates depth so lounges and front rooms feel bigger.
Kerb appeal
Classic feature that lifts the whole frontage.
Warm and quiet
Modern frames, tight seals and high-performance glazing improve comfort.
Flexible layouts
Mix fixed panes with side-hung or top-hung openers where you need airflow.
Not sure which suits your house best
We will show you examples and layouts at survey so you can decide with confidence.
• uPVC in smooth colours or timber-look foils • Aluminium for slim lines and a sharper, modern feel • Dual colour inside and out if you want a softer interior tone any systems
• Fixed centre with side-hung openers for ventilation • Top-hung fanlights above fixed panes for privacy and airflow • Dummy sashes to balance sightlines
• High-performance double glazing as standard • Acoustic or laminated glass for noise and security • Privacy glass for side elevations and bathrooms • Decorative bars to match period patterns
• Cills sized correctly for projection • Angled posts or corner posts that match frame colour • Roof options for bays with canopies • Under-bay cladding or panels renewed to suit the house
A great bay or bow is not just about the frames. It needs proper support and weathering so it lasts.
Low-e coatings, argon-filled units and warm-edge spacers help achieve low U-values so the front room stays comfortable in winter.
Optional acoustic or laminated glass and tight seals reduce road noise on busier streets.
Multi-point locking and robust hinges as standard. Laminated glass available for vulnerable panes.
We visit, measure properly, look at your existing frames and talk through finishes, glazing and hardware. It’s a conversation, not a sales pitch.
You’ll get an itemised quote with the style, colour, glass spec, lead time and warranty. No vague “from…” pricing and no surprises later.
Every frame is built for your apertures. This is what keeps the installation neat and the seals tight.
We protect floors, remove old frames and glass, seal up neatly and clean down. Old materials are taken away. You’re not left with a skip.
If you ever need us, you don’t get pushed to a call centre. You speak to the same team who fitted the job.
We measure properly, check structure and supports, and talk through layouts, bars, colours and glazing.
Clear specification including any support work, lead times and warranty. No vague prices.
Frames built to your sizes for neat lines and consistent compression on seals.
Floors protected, old frames and panels removed, supports fitted where required, edges sealed and trims finished cleanly. All waste taken away.
If you need anything, you speak to the same friendly team who fitted your windows.
Serving Grantham, Stamford, Sleaford, Newark, Bourne, Melton Mowbray and nearby villages.





If we are converting a flat window to a projecting bay, there is usually light building work for the base and roof or canopy. We will outline this clearly in the quote or coordinate with your builder.
Like-for-like replacements usually do not need permission. New projections or changes in appearance may need approval, especially in conservation areas. We will advise before you commit.
Some do. We check at survey. If support is needed, we include poles, brackets or structural posts in the price so the job is safe and compliant.
Yes. We can mirror Georgian or Victorian layouts with astragal bars so the frontage stays authentic.
Modern frames and glazing deliver better insulation than older units. You should feel fewer draughts and a more even temperature.
Warm-edge spacers, low-e glass and correct ventilation reduce the cold band at the edge of the glass that causes condensation.
A straightforward replacement bay is often completed in a day. Conversions from flat to bay or structural renewals can take longer. You will get a realistic schedule with your quote.
Yes. We take away old frames, sealed units and any under-bay cladding we replace. Your frontage is left clean and tidy.
Trustindex verifies that the original source of the review is Google. I have been using Avanti for 35 years and the service and product quality is amazing!Posted on Google Will mcintoshTrustindex verifies that the original source of the review is Google. Cannot recommend Avanti enough!! Amazing service from start to finish. The whole team were friendly and professional. Great job and have told all my family and friends if they ever need a job doing, to give them a callPosted on Google Natalie BuxtonTrustindex verifies that the original source of the review is Google. We had nine blown windows, called a couple of window companies to try and get the best price and these guys were the only ones who got back in touch with us. We weren't willing to wait around so went with them and I'm glad we did. They came out, took the measurements and ordered the glass. I was advised the glass could take about four weeks which was fine. Less than a week later I got a call asking if there was any chance they could come later today to fit our new windows! They came round and had them all replaced in about an hour!! For the first time since we've moved into our house we have been able to see properly out of our window! Thank you for the professional and prompt service! I would recommend.Posted on Google Lisa KnightTrustindex verifies that the original source of the review is Google. We have this week had our windows installed courtesy of Avanti Windows Grantham. From start to finish we have had excellent service. I knew I was in safe hands when I met Richard who came out originally to measure up and quote, but to be honest everyone we have dealt with from Richard through to the fitting team have been spot on. Very professional. We did get quotes from other well known window suppliers but the out dated sales tactics and tedious process put us off. There was none of that with Avanti…. It was so easy. I would highly recommend them. I’d give 6 stars if I could👍🙏Posted on Google MARK GOODETrustindex verifies that the original source of the review is Google. Amazing firm and very professional. They’ve done a great job In replacing our conservatory roof for a solid one. Punctual everyday and end result it brilliant. Highly recommendPosted on Google George PimTrustindex verifies that the original source of the review is Google. Avanti delivers an outstanding service. I had a new glass roof fitted on my conservatory and the team also refurbished the whole conservatory and made it look like it was new. Fantastic job, exceeded my expectations. I have no hesitation in strongly recommending this company. A big thank you to the whole team at Avanti, a great bunch of guys!Posted on Google Douglas HowcroftTrustindex verifies that the original source of the review is Google. Brilliant company. Quality windows. Staff really friendly and helpful.Posted on Google Chris JonesTrustindex verifies that the original source of the review is Google. Absolutely over the moon with my windows and doors, service and fitting is top notch!! We will be having replacement windows from them in the future!!Posted on Google Toni BlakeyTrustindex verifies that the original source of the review is Google. A patio door leaked because they "forgot to put in drain holes". Ahe door got fitted by "trimming" the opening by wacking it with a lump hammer (even though the builder was on hand with a diamond saw), the windows came scratched and the external paint could be removed with a finger. I saw they hadn't sealed in the window frames and asked why not. Apparently they don't carry sealant!?!? They all got taken out and my builder rebuilt the door opening.Posted on Google Sheila and PeterTrustindex verifies that the original source of the review is Google. Tony and the team were very professional throughout the whole process. The fitters had to install all new windows and doors and have completed to a high standard. They have been very accommodating with my timescales and would highly recommend. Thank you!Posted on Google Evie English