How much does a house extension cost in Liverpool in 2026?

Short answer: budget around £3,000 per square metre, including VAT, for a single-storey rear extension in Liverpool, plus the windows and doors. That is the rate our own recent single-storey extensions have been priced at by L4 Property Developments, and it covers the build from footings to plaster. A 20 square metre kitchen extension therefore starts at roughly £60,000 before glazing, drawings and fees. National guides published in 2026 put a standard single-storey extension in the North of England at around £2,000 to £2,450 per square metre for the shell and basic finish, before fees, kitchens and glazing, which is consistent once those are added back.

What the per-square-metre figure includes

Ours covers the building work itself:

• Footings and slab, dug and poured to the engineer’s drawing and inspected by building control
• Drainage alterations under and around the footprint
• Brick and block walls, insulated to current regulations
• A GRP flat roof or a pitched roof, insulated, with roof lights if wanted
• Steels and the knock-through into the existing house
• First and second fix plumbing, plastering, skirtings and architraves

What it does not include

• Glazing. Bifold and sliding doors range from a few thousand pounds to well into five figures, so we price them separately.
• Specialist electrical work. Standard electrics are in our rate and certified by our NAPIT-registered electrician. A consumer unit change, a supply upgrade or anything specialist is priced separately and stated.
• Drawings and fees. An architect for the plans, a structural engineer for the steels, and the building control fee. The building regulations fee alone on a recent Liverpool project of ours was about £1,800.
• The kitchen, bathroom or finishes going into the new space.
• Decorating and landscaping.

What moves the price most

1. Glazing. The single biggest swing on most extensions.
2. The steel. A wide opening into the house, or a beam carrying the first floor, costs more than a simple door-width knock-through.
3. Drains. A sewer under the footprint means a build-over agreement and protected pipework.
4. Ground. Building control decides the footing depth on the day they see the trench; a metre is normal on Liverpool clay, deeper near trees.
5. Roof. A pitched tiled roof costs more than a flat GRP roof, and a lantern or roof lights add to either.
6. Access. A terrace with no side access means everything goes through the house.

Two-storey extensions

The per-square-metre rate for the first floor is lower than the ground floor because the foundations and roof are shared, but the total is obviously higher and a two-storey rear extension nearly always needs a planning application rather than permitted development. We price those from drawings rather than publish a rate.

Planning and building regulations

A single-storey rear extension up to three metres deep on a terraced or semi-detached house, or four metres on a detached house, is usually permitted development; up to six and eight metres is possible under the larger home extension scheme with a neighbour consultation first. Building regulations approval is needed every time. We check your address and tell you which applies before quoting.

How we quote

We walk the house with you, agree what you want, and write a schedule of works with every line priced. A small payment secures the start date, and the rest is staged against dates on the programme rather than a large deposit. Extras are priced in writing before they are done. The service page has the detail: house extensions in Liverpool and Merseyside.

Sources for the national figures: Best Builders UK, house extension cost per m² 2026; HomeOwners Alliance cost guides. Our own figures are from L4 Property Developments quotations issued in 2025 and 2026.