Single-storey, double-storey, side-return, and wrap-around house extensions across Barnet and North London.
Add space, light and value to your home with a fully managed house extension from The Construction Collective. We design and build single-storey rear, side-return, wrap-around and double-storey extensions across Barnet, North London and Hertfordshire.
Get an instant cost estimate for your extension, loft conversion, renovation or new build — tailored to your project in under 60 seconds.
From a kitchen-diner extension with bi-fold doors and a roof lantern, through to a full double-storey side extension adding bedrooms and a bathroom upstairs, we deliver extensions to a premium standard with clear pricing and realistic programmes.
We work with your architect or recommend one of ours, manage planning applications, structural design, party-wall awards and building control sign-off — so the project starts on solid foundations.
House extensions across Barnet, Finchley, Hampstead, Mill Hill, Whetstone, Totteridge, Hendon, Edgware, Radlett, Potters Bar, St Albans and surrounding areas.
Most single-storey rear extensions in Barnet fall under Permitted Development and don't require planning permission, provided they meet size limits. Extensions in conservation areas or above Permitted Development size limits will need full planning permission. We assess this for every client.
A typical single-storey rear extension costs £35,000–£65,000. Side return extensions cost £40,000–£70,000. Wrap-around extensions cost £60,000–£100,000. Double-storey extensions cost £70,000–£120,000. Use our Online Price Guide for an instant estimate.
A typical single-storey rear extension takes 10–14 weeks from start to finish. Double-storey extensions typically take 16–24 weeks. We provide a detailed programme at quotation stage.
We build all types of extension including single-storey rear, side return, wrap-around, double-storey, kitchen extensions and garden room extensions. Visit our dedicated extension sub-pages for full details on each type.
Yes — bi-fold and sliding doors are extremely popular and we install them on the majority of our extensions. We work with trusted glazing suppliers and can advise on the best specification for your project and budget.
Yes — typically 10–20% in the North London market. For properties in Barnet, Finchley and Hampstead, this regularly represents £80,000–£200,000 in added value.
In most cases no — the main disruption is during rear wall removal and structural steel installation, which typically takes 1–2 weeks. After that, the build is largely external and disruption to your daily life is minimal.
Yes — where planning permission is required, we manage the entire application process including preparation of planning drawings, planning statements and all liaison with the London Borough of Barnet planning department.
A transformative wrap-around rear extension creating a sun-drenched open-plan kitchen, living area and utility.
Single-storey rear extension with open-plan kitchen-diner, bi-fold doors and a glazed roof lantern.
A glass-roofed side-return extension unlocking the unused alley and doubling the kitchen.
Get an instant cost estimate for your extension, loft conversion, renovation or new build — tailored to your project in under 60 seconds.
Book a free, no-obligation consultation. We'll visit your home, listen to your brief and tell you honestly what's possible.
Or message us directly on WhatsApp — we typically respond within the hour.
