How much does a house extension cost per m² in Ilford and East London?

Short answer: house extensions in Ilford and East London start from £2,400 per m² for a single-storey rear extension, from £2,600 per m² for a side-return or wrap-around and from £2,200 per m² of floor area for a two-storey extension. A 15 m² kitchen extension starts from about £36,000. These are our own starting rates. Drawings, structural design, Building Control and party wall costs come on top, and we confirm everything in writing after a free survey.

Extension prices per m² from SK Design

Type	Starting price	Notes
Single-storey rear extension	from £2,400 per m²	Built, plastered and ready to decorate. A 15 m² kitchen extension starts from about £36,000.
Side-return or wrap-around extension	from £2,600 per m²	More steel and glazing than a simple rear extension.
Two-storey extension	from £2,200 per m² of floor area	Drawings, structural design and Building Control fees are quoted separately.

Starting prices, not fixed quotes. No VAT is added because SK Design & Construct Ltd is not VAT registered. The full list is on our prices page.

How per-m² pricing works

Builders compare extensions on a cost per square metre because it is a quick way to size a project. You multiply the floor area of the new room by the rate. At £2,400 per m², a 15 m² single-storey extension comes to about £36,000, which is where our kitchen extension figure comes from.

The per-m² rate is only a guide. Small extensions often cost more per m² than large ones, because the fixed costs of site set-up, steel, drainage and a kitchen-grade finish are spread over fewer square metres. A rate also tells you nothing about the things the next section lists, which is why we confirm a written quote after a free survey and do not rely on the rate alone.

What changes the cost of an extension?

• Size and shape. A simple box is cheaper to build than an L-shape or a wrap-around.
• Foundations. Your ground decides how deep and how wide they must be. Trees and drains nearby can change the design.
• Roof type. Flat, pitched or glazed roofs all price differently.
• Glazing. Large bi-fold or sliding doors and roof lights make a room bright but add cost.
• Steelwork. Opening up the back of the house usually needs steel beams. Side-return and wrap-around extensions need more of it.
• Drainage. Many Ilford terraces and semis have a shared sewer across the back gardens. Building over or near a public sewer usually needs Thames Water's agreement.
• Kitchen and finishes. Units, worktops, flooring and underfloor heating are separate from the build rate. See our kitchen fitting page.

Single-storey rear extension

The most popular way to get a bigger kitchen-diner, starting from £2,400 per m². It is built, plastered and ready to decorate. Many single-storey rear extensions on houses are permitted development within size limits, which can save a planning application.

Side-return and wrap-around extensions

A side return uses the side passage on Victorian and Edwardian terraces. A wrap-around combines rear and side for the largest ground-floor space. Both start from £2,600 per m². The higher rate reflects extra steel and glazing, and the work often sits right on the boundary, so party wall notices are likely.

Two-storey extension

A two-storey extension adds bedrooms or a bathroom above the new ground-floor room. It starts from £2,200 per m² of floor area. The rate is per m² of floor area, so the upper floor counts as well as the ground floor. It usually needs full planning permission. Drawings, structural design and Building Control fees are quoted separately.

Extras that are not in the starting price

• Drawings. Needed for Building Regulations, and for planning or prior approval where required.
• Structural engineer. Calculations for steel beams, foundations and openings.
• Building Control. Inspections of the foundations and the build. Every extension needs Building Regulations approval.
• Party wall costs. Notices under the Party Wall etc. Act 1996 and any neighbour's surveyor.
• Planning fees, where permission is needed.

We show these as separate lines on your written quote. We do not put numbers on them here, because they depend on the size and position of the extension.

Permitted development or planning permission?

Many single-storey rear extensions on houses can be built under permitted development, within size limits and with prior approval for larger ones. Flats and maisonettes, listed buildings and conservation areas have stricter rules, and double-storey and side extensions often need full planning permission. Our guide explains the limits: Do I need planning permission for an extension or loft conversion in Redbridge?

Party walls and neighbours

Rear and side-return extensions on terraces often need foundations close to, or on, the boundary. That normally brings in the Party Wall etc. Act 1996, so notices go to the neighbours before work starts. Talking to them early saves time and stress.

How to get an accurate price

1. Decide which type you want: rear, side return, wrap-around or two-storey.
2. Measure roughly how deep and wide the new room will be, and multiply to get the m².
3. Think about glazing and the kitchen. They move the total more than most people expect.
4. Call 07774 944042 to book a free survey. We check the drains, the ground and the planning position, then give you a written, itemised quote.

Read more on our house extensions page. Thinking of going up instead? See our loft conversions page and the loft conversion cost guide. For a whole-house project, see full renovations. We cover Ilford, Redbridge, Romford, Barking and the rest of East London and Essex.

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SK Design & Construct Ltd, 6 Spurway Parade, Woodford Avenue, Ilford IG2 6UU. Call or WhatsApp 07774 944042 or email info@skdesignconstructltd.com. Registered in England and Wales, company number 16582978.