Loft Conversion and House Extension London and Hertfordshire
Save time, money and disruption by combining your loft conversion and house extension into one project with LCCL Construction. We design and build combined schemes across London and Hertfordshire — one company, one contract, one project manager handling everything from architecture to completion. LABC Award Winners 2024. Over 200 reviews rated 4.7 out of 5.
LABC Awards
Winners 2024
200+ Reviews
4.7 / 5 Rating
NFB Members
LABC Partners
Why Combine a Loft Conversion and House Extension?
Combining a loft conversion with a ground floor extension is the most comprehensive way to transform your London home. By completing both projects together under one design and build contract, you gain maximum additional space — extra bedrooms and bathrooms in the loft, plus enlarged kitchen, dining and living areas on the ground floor — while saving time, money and disruption compared to doing them separately.
A combined project allows the architectural design to consider the whole house as one scheme. Internal layouts, staircases, structural steelwork and services can be planned together for a better overall result. You also save on preliminaries — scaffolding, skip hire, project management and site setup — because these costs are shared across both elements rather than duplicated.
LCCL Construction specialises in combined loft conversion and house extension projects across London and Hertfordshire. With over 20 years of experience, LABC Awards Regional Winners 2024 and 200+ reviews rated 4.7/5, we are one of the most experienced companies in London for managing large-scale residential projects that combine multiple elements into a single seamless build.
How Much Does a Combined Project Cost?
A combined loft conversion and ground floor extension in London typically costs between £70,000 and £150,000 depending on the types of conversion and extension, the size of the property and the level of specification:
Dormer loft conversion + rear extension: £70,000 to £110,000.
Hip to gable loft conversion + rear extension: £80,000 to £120,000.
L-shaped loft conversion + wraparound extension: £100,000 to £150,000.
Combined projects typically offer 10% to 15% savings compared to completing each element separately, because shared costs such as scaffolding, structural engineering, project management and building control are not duplicated.
Get an instant quote at lcclconstruction.co.uk or call 020 8037 7332.
Subject final drawings, how big the area is, location, finishing, structural drawings, alteration, time when, costs subject to change.
What Is the Process?
Our design and build process for combined projects follows the same structured approach as all LCCL Construction projects:
Phase 1 — Design: Free consultation, measured building survey, architectural design for both the loft and extension as one coordinated scheme, planning applications and building regulations.
Phase 2 — Pre-construction: Structural engineer calculations, party wall agreements, material procurement and construction planning.
Phase 3 — Construction: The ground floor extension and loft conversion are typically built concurrently, with groundworks and the extension starting first while scaffolding is erected for the loft. This parallel approach reduces the overall build time.
Phase 4 — Completion: First and second fix, plastering, decoration, kitchen and bathroom fitting, building control sign-off and snagging.
Total timeline is typically 6 to 9 months from consultation to completion.
What Is Included?
Our full design and build service covers everything for both the loft conversion and extension: consultation, measured survey, architectural design, planning, building regulations, structural calculations, party walls, all construction, electrics, plumbing, plastering, decoration, building control sign-off and optional 10-year LABC warranty. One company, one contract, one project manager.
Areas We Cover
We design and build combined loft conversion and extension projects across London and Hertfordshire including Barnet, Finchley, Hendon, Muswell Hill, Highgate, Hampstead, Southgate, Enfield, Edgware, Borehamwood, St Albans, Potters Bar, Bushey, Watford, Ealing, Clapham, Putney, Wandsworth, Hackney, Islington, Camden and all surrounding areas. Call 020 8037 7332.
Frequently Asked Questions
How much does a combined loft conversion and extension cost?
A combined loft conversion and house extension in London typically costs £70,000 to £150,000. Dormer loft + rear extension from £70,000, hip to gable loft + rear extension from £80,000, L-shaped loft + wraparound from £100,000. Combined projects save 10% to 15% compared to doing them separately. Subject to variables such as final drawings, structural drawings, finishing, how big it is, location, alterations, surveys and costs subject to change.
Is it cheaper to do a loft conversion and extension at the same time?
Yes. Combining both projects into one build saves 10% to 15% on total costs because shared expenses such as scaffolding, structural engineering, project management, skip hire and building control are not duplicated.
How long does a combined loft conversion and extension take?
A combined project typically takes 16 to 24 weeks to build, with a total timeline of 6 to 9 months from initial consultation to completion. The extension and loft conversion are built concurrently, which is faster than doing them as separate projects.
Do I need planning permission for a combined project?
The loft conversion element usually falls under permitted development for most house types. The extension element depends on the size and type. LCCL Construction assesses both elements and handles all planning applications and building regulations.
Can I live in my house during a combined project?
Yes. There will be more disruption than a single project but most homeowners remain in the property throughout. LCCL Construction plans the build sequence to minimise disruption to your daily life.
How do I get started?
Call us on 020 8037 7332, book a free consultation at lcclconstruction.co.uk, or get an instant quote online.