Small Side Infill Flat Roof
Small Side Infill Flat Roof House Extensions: A Smart Choice for London Homes
If you live in London and feel like your home is bursting at the seams, you’re not alone. The city’s high property prices mean moving to a bigger house isn’t always practical. This is where a small side infill flat roof house extension can work wonders.
By utilizing that often overlooked strip of land running alongside your house — especially in Victorian and Edwardian properties — you can expand your home in a way that feels natural and cohesive. Best of all, a flat roof design keeps costs manageable while giving your home a sleek, modern look.
I’ve helped many London homeowners with side infill extensions, and the results are always transformative. In this article, I’ll guide you through everything you need to know: costs, planning permissions, design tips, and the areas where this type of extension thrives. Let’s dive in.
What is a Small Side Infill Flat Roof Extension?
A small side infill extension fills the narrow gap between the side of your house and the boundary wall or fence. These are particularly common with Victorian and Edwardian terraced houses that have small alleys running alongside them.
Why Choose a Flat Roof?
A flat roof is often the go-to for these extensions. It’s simple, cost-effective, and ideal for skylights or glazed panels, maximizing natural light. Unlike pitched roofs, flat roofs maintain a low profile, ensuring the extension feels subtle and doesn’t overshadow the rest of the property.
When I worked on a project in Camden Town, the homeowners were hesitant about a flat roof, thinking it might look too industrial. But after adding large skylights, the space became flooded with light, turning a previously dark kitchen into the most inviting room in the house.
How Much Does a Side Infill Flat Roof Extension Cost in London?
Average Cost Breakdown
Pricing can vary depending on the level of finish and complexity, but here’s a rough guide:
- Basic build (no frills): £2,355 per sqm
- Mid-range quality: £2,800 per sqm
- High-end finish: £3,530 per sqm
For a standard single-storey side infill extension, expect to pay between £40,000 and £65,000. If you want a more luxurious finish or a two-storey extension, this could rise to £100,000 or more.
Additional Costs to Consider:
- Architect and engineer fees: 15-20% of the build cost
- Planning application fees: Around £206
- Building control fees: Approximately £900-1500
- VAT: 20% on the total cost
It’s worth noting that costs can fluctuate depending on your location within London. For instance, building in Fulham or East Dulwich tends to be pricier due to the higher demand for quality tradespeople.
Where Are Side Infill Extensions Most Popular in London?
Hotspots for Side Infill Extensions
This type of extension is hugely popular across London, but certain areas see more of them due to the architectural style of homes:
In these neighborhoods, Victorian and Edwardian houses dominate, and their narrow side alleys make them perfect candidates for infill extensions. The result is often a wider kitchen or dining area that opens up into the garden.
In contrast, areas like Hackney Wick or Stoke Newington often have larger plots, so rear or wrap-around extensions are more common.
Which Homes Are Best Suited for Side Infill Extensions?
Victorian and Edwardian Terraces
These houses were built with narrow side returns that create dark, underused kitchen spaces. By filling this side space, you can create a larger open-plan kitchen or living room.
In one project I worked on in Kensal Rise, the homeowners added a side infill to their terrace and converted the previously cramped kitchen into an airy, modern entertaining space that felt twice as big.
Semi-Detached Homes
Side infill extensions also work well for semi-detached properties, particularly if the side of the house sits along a driveway or alleyway. The extension can blend seamlessly with the existing house, adding valuable living space without eating into the garden.
Key Design Considerations
Maximizing Natural Light
One of the biggest concerns with side infill extensions is the potential loss of light. Here are some ways to combat that:
- Skylights or roof lanterns: Installing these in the flat roof can flood the space with daylight.
- Glazed panels: Glass walls or doors leading to the garden can help maintain brightness.
- Internal windows: If the extension blocks existing windows, adding internal glazing can let light pass between rooms.
Cohesive Design
Your extension should complement the existing house, not clash with it. Use materials that echo the original architecture. For instance, exposed brick or Crittall-style doors can preserve that classic London terrace aesthetic.
In a Fulham project, we used reclaimed bricks to match the extension with the original Victorian facade. The result looked like it had always been part of the house.
Planning Permission and Building Regulations
Do You Need Planning Permission?
In many cases, side infill extensions fall under permitted development if they meet certain criteria:
- Single-storey and no higher than 4m
- No wider than half the width of the original house
- Uses similar materials to the existing property
However, if your property is in a conservation area (such as parts of Camden or Fulham), full planning permission may be required.
Building Regulations
Even if planning permission isn’t needed, your extension will still need to comply with building regulations. This ensures structural safety, insulation, and fire safety standards are met.
FAQ (Frequently asked questions)
Q1. How long does it take to build a side infill extension?
Typically, a small side infill extension takes around 3 to 4 months to complete, depending on the complexity and size of the project.
Q2. Will a side infill extension add value to my home?
Yes, a well-executed side infill extension can add significant value to your property, often increasing the resale price by 10-15%.
Q3. Do I need to inform my neighbors?
Yes, under the Party Wall Act, you are required to notify your neighbors if your extension affects shared walls or boundaries.
Q4. Can I build a two-storey side infill extension?
It’s possible but may require full planning permission and careful consideration of overshadowing and privacy issues.
Q5. What are the common challenges with side infill extensions?
Common challenges include loss of natural light, drainage issues, and ensuring seamless integration with the existing structure.
Final Thoughts
A small side infill flat roof house extension can unlock the hidden potential in your home, providing valuable extra space without breaking the bank. Whether you’re dreaming of a larger kitchen, a light-filled dining room, or just more breathing room, this type of extension offers a practical and stylish solution.
Thinking about adding one to your home? Reach out to our professional architects or builders with experience in side infill projects. Trust me, the transformation will be worth it — and it’s a lot easier (and cheaper) than moving to a bigger house in London!
