How much does a loft conversion cost in London and Kent in 2026?

Loft conversion cost ranges in 2026

Loft conversion pricing in London and Kent has stabilised through 2026 after the volatility of 2022–2024. Material prices have softened in most categories, but labour rates — particularly for qualified carpenters, electricians and gas-safe engineers — have not. Honest 2026 ranges for an averagely complex London or Kent property look like this: Velux conversions £45,000–£60,000; rear-dormer conversions £55,000–£85,000; hip-to-gable with rear dormer £75,000–£105,000; mansard conversions £85,000–£120,000+.

Those numbers assume a single en-suite, a properly designed staircase, full Building Regulations compliance and a finished standard you would actually want to live with. They do not include high-end fittings, structural complications discovered in survey, or bespoke architectural glazing.

When you see headline prices £15,000–£20,000 below those ranges, scope is almost always being stripped out — usually structural design, proper insulation, fire-rated doors, or genuine Building Regulations sign-off. We see those projects on rescue jobs frequently.

What drives the cost of a loft conversion

Five factors do most of the work on price. First: structural complexity. The bigger the steels and the more the existing roof needs rebuilding, the higher the cost. Mansards always sit at the top of this list.

Second: planning route. A simple permitted-development rear dormer is faster and cheaper than a full planning application with neighbour objections. Conservation areas and Article 4 directions can add £8,000–£15,000 in design, surveying and planning support before a brick is laid.

Third: staircase position. A staircase that lands cleanly off the existing upstairs hallway is straightforward. One that requires re-planning a bedroom, moving a soil stack, or borrowing structural floor area is significantly more expensive.

Fourth: en-suite plumbing. Adding a shower room in the loft means routing soil pipes, hot water and cold water supplies up through the property. A property with a combi boiler at first-floor level is easier than one with a basement gas supply.

Fifth: finishes. The same shell can absorb £8,000 of standard finishes or £25,000 of high-end joinery, tiling and bathroom fittings. We separate shell costs from finish costs in our quotes so you can see exactly where the money goes.

Cost differences across London and Kent

Within London, our typical 2026 cost spreads look like this: East and South-East London (E, SE, DA postcodes) sit at the lower end of the range; North and West London (N, NW, W) typically run 8–15% higher driven by logistics, parking and labour competition; Kent commuter belt (BR, TN, ME) tracks below central London by roughly 5–10%.

These spreads matter most for the structural shell. Finishes are largely market-priced and vary less by postcode. Project management, professional fees and statutory costs (planning fees, Building Regs charges, structural calculations) are essentially flat across the region.

What to budget for beyond the build cost

A complete project budget needs more than just the builder’s number. Realistic 2026 additional costs include: architectural drawings £2,500–£5,000; structural engineer’s calculations £900–£1,800; planning application fees from £258; Building Regulations charges £600–£1,200; party wall agreements £900–£1,500 per neighbour; and a 5–10% contingency on the build itself.

For a typical £75,000 build, that adds £8,000–£14,000 of additional costs. We give clients a full all-in budget at the project review stage rather than just the headline construction figure.