Is 50k enough for an extension?
In Fulham, £50,000 is below the realistic cost of a full side-return or rear extension, which starts around £60,000 for the shell and services before the kitchen. £50,000 can build a small rear extension of 10 to 14m², or a garden room, but not a typical Victorian side return.
London extension costs run £3,000 to £4,500 per square metre excluding VAT for a good-quality single-storey build. At those rates £50,000 buys 11 to 16m² — a modest rear extension roughly 4m wide by 3m deep. A typical Fulham side-return infill is 18 to 22m², which puts it at £60,000 to £90,000 before fit-out.
The figures people find online quoting £30,000 to £40,000 extensions are generally either outside London, several years old, or excluding significant elements — foundations to the depth London clay requires, party wall costs, structural steel, professional fees and VAT. Any of those omitted makes a headline number look achievable when it is not.
What genuinely brings the cost down is simplicity. A rectangular extension with a solid roof, standard glazing and no change in floor level costs far less per square metre than the same area with a glazed roof lantern, structural glass corners and bifolds. The glazing package alone can be £15,000 to £30,000 on a Fulham side return, and it is the most common place a budget quietly doubles.
If £50,000 is firm, the honest options are a smaller footprint, a simpler specification, or reconfiguring internally instead. Removing the wall between a back-addition kitchen and the rear reception often delivers much of the feeling of an extension for a fraction of the cost, and on a Fulham terrace it is frequently the better value decision.
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