Timber - PVC - Aluminium - Windows, Doors & Conservatories in Hampshire
Bay Windows
Bay Windows
A bay window is a multi-pane, projected window assembly consisting of three or more units that angle outwards from a building’s exterior wall. Commonly featuring a larger central “picture” window flanked by smaller units, they increase interior floor space, create window seats, and maximise natural light. Common styles include splay, square, and bow, often available in uPVC, timber, or aluminium.
| Feature | Overview |
|---|---|
| Structure | Protrudes beyond the exterior wall, often used for seating or to make a room feel more spacious. |
| Key Styles | Splay Bay (classic angled sides), Box Bay (90-degree projection), and Bow Window (curved configuration). |
| Planning | New, front-facing, or significantly altered bay windows may require planning permission. Direct replacements usually do not. |
Table of Contents
1. Key Features & Types of Bay Windows
Understanding the exact terminology will help you define what is best for your living rooms, dining areas, or bedrooms to create cozy, bright spots.
🏠 Common Configurations
- Splay Bay: The classic design with a flat front window and angled sides (usually 30 or 45 degrees). Very popular in Victorian homes.
- Box Bay: A rectangular, 90-degree projection. It resembles a small extension and offers maximum internal floor space.
- Bow Window: A beautifully curved configuration, usually consisting of five equal-sized panes that create a gentle semi-circle.
2. Materials & Finishes
Modern manufacturing means you are no longer limited to high-maintenance materials. Bay windows are now available in uPVC, timber, or aluminium, with various color options including classic white, contemporary anthracite grey, and highly realistic wood effects.
3. The Benefits: Light, Space & Views
Installing a bay window transforms how you experience a room. Here is why they are so popular:
- Natural Light: Because they project outwards, they capture sunlight from three different angles, allowing more light into a room compared to flat, flush windows.
- Space & Views: They add extra, usable floor space and panoramic views, perfectly connecting your interior to your garden.
- Aesthetics: They provide a classic architectural feature that boosts kerb appeal, highly popular in both Victorian and modern homes.
4. Estimated Costs for 2026
Pricing varies significantly based on material choice and the amount of structural work required. Here is a realistic guide for the UK market in 2026:
| uPVC Bay Window (3-Section) | £2,000 – £2,900+ |
| Aluminium Bay Window | £3,000 – £4,500+ |
| Timber Bay Window | £5,000+ |
| Converting Flat Window to a Bay | £3,000 – £6,000+ (Includes building/roofing work) |
5. Considerations: Usage & Structural Support
Before proceeding, it is crucial to understand the rules around installation and the structural requirements of your property.
If you are replacing an existing bay window with one of the exact same size, you usually do not need planning permission (Permitted Development applies).
New, front-facing, or significantly altered bay windows may require planning permission from your local authority.
6. Frequently Asked Questions
New, front-facing, or significantly altered bay windows may require planning permission. However, directly replacing an existing bay window usually falls under Permitted Development.
Older single-glazed bays can be draughty, but modern uPVC, timber, or aluminium bays from KJM feature A-rated double or triple glazing. We also ensure the roof and under-sill cavities are properly insulated to prevent cold spots.
Yes, but it involves building work. We must remove the flat window, build a new brick base (or install brackets for an Oriel window), and construct a new roof for the bay. It is a bigger job but transforms the room.
Yes. Estate agents often cite bay windows as a key selling point because they increase the perceived square footage and natural light, adding character that flat-windowed homes lack.
📚 Knowledge Hub: Choose Your Material
Explore the different window systems we can use to construct your perfect bay window:
- Residence 9 Windows: The ultimate timber-alternative for heritage homes and conservation areas.
- Timber Windows: Authentic, sustainably sourced wooden frames for unparalleled classic charm.
- Vertical Sliding Sash: Perfect for recreating traditional Victorian splay bays.
- Flush Casement Windows: A sleek, flat finish ideal for modern box bays or minimalist properties.
- Bay vs Bow Windows: What’s the difference between a bow and bay.
Ready to Transform Your Home?
Whether you need a sympathetic timber replacement for a Victorian terrace or a sleek aluminium box bay for a modern extension, KJM Group has the structural expertise you need.
Get a Free Bay Window Quote
Mark Pearce is a highly experienced specialist in the double glazing industry, having built his knowledge from the ground up through hands-on experience in installation, manufacturing, sales, and business management. Beyond his role at KJM, Mark is a keen blogger, writer, and traveller, often sharing insights on the latest innovations in the home improvement industry.
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