If you are weighing up a single storey brick extension in London, the figure you really want is a believable cost, not a glossy estimate. This guide breaks down realistic 2026 ranges, what pushes the price up or down, and the hidden costs that catch most homeowners out.
As a working figure, a single storey brick extension in London typically lands somewhere between £2,200 and £3,200 per square metre for a good quality build. A modest 15 sqm rear extension therefore tends to fall in the £33,000 to £48,000 bracket, while a larger 25 sqm kitchen and dining space can run from £55,000 to £80,000 or more.
London sits at the higher end of national figures, largely because of labour rates, restricted site access, parking and permit costs, and skip and waste charges that are simply dearer here than elsewhere. Inner London boroughs such as Camden, Islington and Hackney usually price above outer boroughs like Enfield, Barnet or Haringey.
Two extensions of the same size can differ by tens of thousands depending on specification. Brick choice matters a great deal in London, where matching an existing London stock or a period facing brick can mean sourcing reclaimed or specialist bricks at a premium. Foundations are the other big variable: clay soils, nearby trees and shallow drains often mean deeper trench fill or even piled foundations, which adds cost before a single brick is laid.
The brickwork and structure are only part of the picture. Professional fees, statutory costs and finishes routinely add 15 to 25 per cent on top of the build figure, and leaving them out is the most common reason budgets blow.
A party wall agreement is a near certainty for terraced and semi detached London homes, and surveyor fees commonly run from £700 to £2,000 per neighbour. Planning drawings, structural calculations and Building Control all carry their own charges too.
The smartest savings come from good decisions early, not from squeezing the build later. A clear, detailed specification lets builders price accurately and stops the costly variations that creep in when a job is loosely defined. Get the design settled, the bricks chosen and the kitchen layout fixed before work starts.
Always compare like for like quotes that break down labour, materials and fees separately. A suspiciously low price usually means something has been left out, and in London that often turns out to be the foundations, the steels or the making good of the existing wall.
Many rear extensions fall under permitted development, but limits are tighter for terraced houses, conservation areas and flats, all common in London. It is worth confirming with your borough or applying for a Lawful Development Certificate before building.
Most single storey extensions take around 10 to 16 weeks on site once work begins, depending on size, weather and complexity. Design, planning and party wall arrangements beforehand can add several more months.
A poor brick or mortar match is one of the most visible signs of a cheap extension and can affect resale value. On older London homes, matching often means sourcing reclaimed bricks and using a lime based mortar to blend with the original wall.
Tell us about the job and we will quote within 48 hours.
North London brickwork. Two trowels, one company, on every job from start to finish.