Single-storey extensions in Hertfordshire

Covering Hertfordshire

We cover Hertfordshire, including Watford, Hemel Hempstead, Stevenage and St Albans, and the towns around them.

Homes in the East of England

Housing in the East of England ranges from post-war estates and modern developments to timber-framed and period homes in historic towns, so permitted development checks and conservation controls both feature regularly.

What does a single-storey extension involve?

We design the extension around how you use the house: where the light comes from, how the new room joins the old one, and what happens to the drains and the garden. The structure is built in brick or block to match the house, finished with a flat roof and lantern or a pitched roof, then insulated, plastered and handed back ready to decorate.

Building control application and inspections
Brickwork, roof, glazing and insulation
First-fix and second-fix electrics, plastering and making good

How much does a single-storey extension cost in Hertfordshire?

What single-storey extensions typically cost. These are guide ranges; the written quote for your house replaces them.

Single-storey extensions	Guide price incl. VAT
Standard specification	£2,600 to £3,000 per m²
Good specification	£3,000 to £3,500 per m²
High specification	£3,500 to £4,000 per m²

What approvals does a single-storey extension need in England?

English projects need planning clearance from the local council, building regulations sign-off from building control, and party wall notices where the work is on or near a shared boundary. We prepare and manage all three.

In England a single-storey rear extension can often go ahead under permitted development: up to 3 m deep on an attached house or 4 m on a detached one, no higher than 4 m, with eaves no higher than 3 m within 2 m of a boundary. Deeper extensions, up to 6 m or 8 m, need prior approval from the council first.

What should I think about before starting?

Building on or near a shared boundary usually means serving a party wall notice in England and Wales.
Kitchens and doors have long lead times, so we order them early.

What happens after I enquire?

Send us the details. Give us a postcode, a rough idea of size and some photos, by phone, form or the guide price tool.
Survey at your house. We look at the existing structure, services and access, and agree what the design needs to achieve.
Drawings, approvals, written quote. We prepare the design, apply for the approvals it needs, and give you a fixed price in writing.
We build it. Work follows an agreed programme, with inspections at each stage and a final sign-off.

What people ask before starting

How much does a single-storey extension cost?

Most single-storey extensions cost about £2,600 to £4,000 per square metre including VAT, depending on specification, glazing and ground conditions. We give a fixed price in writing for the agreed specification after the survey.

Do you need to dig up the drains?

Sometimes. If a public sewer runs under the extension, the water company has to agree a build-over or a diversion. We check this at survey stage.

Who deals with the council for a project in Hertfordshire?

We do. We prepare the drawings, submit planning or permitted development paperwork if needed, and arrange building control inspections.

Also covering

Learn more about single-storey extensions, or see every project we cover in Hertfordshire.