What extensions actually cost this quarter

Every quarter we go back through recent project costs and update the figures behind the cost guides. Here is what moved.

Down: structural steel

A typical goalpost frame for a rear extension is roughly eight per cent cheaper than it was a year ago. Nothing to celebrate on a single project, but if you have a wide opening, a five metre run of steel is now a few hundred pounds less.

Flat: glazing

Slim framed sliding systems have stopped climbing. The gap between standard doors and a premium system is still the single biggest lever on a build cost, at fifteen thousand pounds or more, but it is no longer widening.

Up: labour in the South East

Twenty to thirty per cent above the national average, and the gap grew again this quarter. If you are in London or the Home Counties, use the London and South East settings in the calculator rather than the UK average. It is the difference between a budget and a surprise.

What we changed

• Regional multipliers for London and the South East, nudged upward.
• The structural line item in every breakdown, nudged down.
• Nothing else. The rest held.

If you priced a project in the spring and have not started, the number is probably still right. If you are in the South East, it is probably a little low.

Written by the Extnd planning teamWe read the decision notices so you do not have to. If something here applies to your house, the Project Calculator will tell you in a minute.

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VerdictPermitted development

£62,000