Flat Roof Extensions London
Build Your Flat Roof Extension
Balanced Payment Schedules
Contracts Completed On Time
10 Year Warranty On All Work
Tradesmen That You Can Rely On
Create a modern, spacious extension with a high-quality flat roof extension expertly designed and built by LXR Construction. We specialise in flat roof extensions across London, delivering contemporary, light-filled spaces that maximise floor area and suit both modern and period homes. Whether you want a sleek single-storey flat roof extension, a minimalist open-plan kitchen, or a cost-effective upgrade to your existing layout, our team handles everything — from early design concepts and planning to structural engineering and full interior completion.
Why Build a Flat Roof Extension?
- A Modern, Clean and Contemporary Look – Flat roof extensions are perfect for homeowners who prefer a modern architectural style. Their clean lines, smooth edges and large spans are ideal for creating striking open-plan living spaces.
- Perfect for Roof Lanterns & Large Glazing – Flat roofs allow for oversized roof lanterns, skylights and wide sliding or bi-fold doors — making it easy to flood your home with daylight and create a seamless indoor-outdoor connection.
- Cost-Effective & Versatile – Flat roof extensions are typically more affordable than pitched roof builds due to simpler construction. They’re ideal for maximising floor space on a budget without compromising on design or function.
- Ideal for London Properties – London homes, especially terraced and semi-detached properties, often have space constraints. A flat roof extension is a flexible solution that blends discreetly with older architecture or serves as a bold contrast for a modern aesthetic.
- Great for Green Roofs – Flat roofs can accommodate living roofs (green roofs), terrace areas, or improved insulation systems — adding environmental benefits and extra outdoor usability.
Take the first step toward the flat roof Extension you’ve always dreamed of….
Our Step By Step Process To Building Your Flat Roof Extension
1
Consultation & Design
We start by understanding how you use your home and what you want to achieve. Our designers explore modern layouts, roof lantern positions, skylights, glazing options, ceiling heights and how to integrate the extension smoothly with your existing rooms. We then create a customised design focused on space, light and contemporary living.
2
Planning & Approvals
Flat roof extensions may fall under permitted development in some cases, but larger designs typically require full planning permission. We handle everything — architectural drawings, planning submissions, structural calculations, party wall agreements and building regulations compliance — ensuring a stress-free experience.
3
Construction & Project Management
Our expert flat roof extension builders deliver high-quality workmanship at every stage. A dedicated project manager oversees all phases including groundworks, steel installation, brickwork, insulation, flat roofing systems (GRP, felt, EPDM), skylights and glazing, plus full interior works. You receive regular updates from start to finish.
4
Completion & Interior Fit-Out
After construction, we complete the space with flooring, lighting, plumbing, heating, carpentry and decoration. We then conduct a full quality inspection and guide you through your new extension, ensuring every detail meets our high standards.
How Much Does A Flat Roof Extension In London Cost?
Prices depend on size, structural requirements, glazing choices and level of finish. As a guide:
- £55,000 – £95,000+ for a standard single-storey flat roof extension
- £95,000 – £150,000+ for open-plan designs with roof lanterns, large glazing and premium finishes
After your consultation and survey, we provide a detailed, itemised quote.
Will a Flat Roof Extension Add Value to your home
Yes adding a flat roof extension to any home will add value, simply because of the additional space it gives a buyer. However, it depends on the size and design. A large flat roof extension in a kitchen like in the image at the top of this page could add considerable value because it not only increases the size of the house but also floods the room with light utilising the flat roof to add a modern sky light. A flat roof extension like this could increase your property value by 10–20%.
Frequently Asked Questions
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Our Flat Roof Extension Building Services in London
From stylish modern designs to character-preserving builds for period homes, we offer a complete suite of services:
Single Storey Flat Roof Extensions
A cost-effective way to expand your kitchen, dining room or living space with a clean, modern flat roof structure.
Modern Kitchen Flat Roof Extensions
Create a bright open-plan kitchen with roof lanterns, wide glass doors and premium interior finishes.
Rear & Side Flat Roof Extensions
Extend into unused garden or side space while maintaining a low-profile roofline that suits both old and new homes.
Flat Roof Extensions with Roof Lanterns
Maximise natural light and create a stunning architectural feature with modern roof lantern designs.