House Extensions
London & Hertfordshire
Transform your home with a professionally designed and built house extension. TCM Building has delivered over 200 extensions across London and Hertfordshire — from simple rear additions to complex double-storey projects.
The Most Popular Way to
Add Space & Value
A house extension is a permanent structure added to an existing residential property to increase its floor area. Unlike a loft conversion or basement conversion, a house extension typically extends the footprint of the property outwards — to the rear, side, or both — creating new ground-floor or multi-storey living space.
For homeowners in London and Hertfordshire, a house extension is often the most practical alternative to moving — avoiding stamp duty, estate agent fees, and the upheaval of relocation, while creating a home that is precisely tailored to your family's needs.
TCM Building manages the entire process from initial design through to final decoration, including all structural engineering, planning applications, and specialist trades. You deal with one team, one contract, and one point of contact throughout.
Which Extension Is Right for You?
Rear House Extensions
A rear extension is the most common type of house extension in London and Hertfordshire. It extends the back of your home into the garden, typically creating a larger kitchen, open-plan kitchen-diner, or additional living space. Under Permitted Development rights, a single-storey rear extension can extend up to 3 metres on a semi-detached or terraced house, and up to 4 metres on a detached house — without planning permission.
How We Deliver Your Extension
Free Consultation & Site Visit
We visit your property, discuss your vision, assess feasibility, and take initial measurements. No obligation, no charge.
Design & Planning
Our in-house design team produces architectural drawings. We advise on Permitted Development vs. planning permission and submit applications on your behalf.
Structural Engineering
A qualified structural engineer calculates all load-bearing requirements, foundation specifications, and steel beam sizes.
Detailed Quotation
We provide a fully itemised, fixed-price quotation with no hidden costs. You know exactly what you're paying before work begins.
Construction
Our dedicated site team carries out all works — groundworks, brickwork, roofing, glazing, plastering, and first-fix services — under one contract.
Finishing & Handover
We complete all second-fix works, decoration, and snagging. We don't leave until you're completely satisfied.
Do You Need Planning
Permission?
Many house extensions in England can be built under Permitted Development rights, meaning no formal planning application is required. However, the rules are complex and depend on your property type, location, and the size of the proposed extension.
TCM handles all planning applications and Building Regulations submissions on your behalf. We have an excellent track record of securing planning approval.
House Extension Cost Guide
Prices vary based on specification, materials, and site conditions. These figures are indicative guides for London and Hertfordshire. We provide a fixed-price quotation after the free site visit.
| Extension Type | Size | Typical Cost | Build Time | Planning |
|---|---|---|---|---|
| Single-Storey Rear | Up to 30m² | £35,000 – £65,000 | 10–16 weeks | Often PD |
| Single-Storey Rear | 30–50m² | £65,000 – £90,000 | 14–18 weeks | Often PD |
| Side Return | 15–25m² | £40,000 – £80,000 | 12–18 weeks | Often PD |
| Wrap-Around | 40–70m² | £80,000 – £150,000 | 20–28 weeks | Usually required |
| Double Storey | 40–80m² | £60,000 – £140,000 | 16–24 weeks | Required |
PD = Permitted Development. All prices are indicative and exclude VAT. A fixed-price quotation is provided after the free site visit.
The TCM Difference
Building an extension is one of the largest investments you'll make in your home. Choosing the right contractor is critical. Here's why over 200 London and Hertfordshire homeowners have trusted TCM with their extension projects.
We manage all trades — structural engineers, bricklayers, roofers, plumbers, electricians — under one contract. No coordination headaches.
Our detailed quotations are fixed-price. No surprise invoices, no scope creep. What we quote is what you pay.
Every project has a dedicated site manager who is your single point of contact from groundworks to handover.
We are independently verified on Checkatrade with a 5-star rating from over 100 verified reviews.
All structural work is backed by a 10-year workmanship guarantee, giving you complete peace of mind.
"TCM built a stunning rear extension and side return for us. The whole process was seamless — from the initial design meeting to the final handover. The quality of the brickwork and the bi-fold doors is exceptional. We couldn't be happier."
Ready to Get Started?
Book a free, no-obligation site visit. We'll assess your property, discuss your vision, and provide a detailed quotation.
House Extension FAQs
Get Your Free Extension Quote Today
Call us or submit an enquiry and we'll arrange a free site visit at a time that suits you.