2026 Building Regulations Changes: What Homeowners Planning an Extension Need to Know

Short answer: the Future Homes Standard, published in March 2026, sets much stricter carbon and energy rules for new dwellings, phased in through to March 2028 — but it's targeted at new-build homes, not most home extensions. What matters for an extension is that it still meets current Part L energy efficiency requirements for the new floor area being added.

What the Future Homes Standard actually does

The Future Homes Standard requires new homes to produce at least 75% lower carbon emissions than the 2013 standard, effectively ruling out gas boilers in new-build properties and requiring solar PV as a core part of the design. It takes effect for new building work from 25 March 2027, with a further transition period for projects already under way, running through to March 2028. It applies to new dwellings being created — most straightforward house extensions to an existing home fall outside its scope.

Where it could still touch your project

If your project involves creating a genuinely new, self-contained dwelling — an annexe with its own kitchen and services, for example, or converting a garage into a separate unit — it's worth raising the Future Homes Standard timetable with your designer early, since it could affect the heating system and glazing specification depending on when the project is submitted and built. For a standard extension to your existing home, current Part L rules on insulation, glazing and airtightness for the new area still apply as before.

What this means for planning permission

None of this changes whether your extension needs planning permission — that's still governed separately by permitted development rules and your property's specific circumstances. See our guides on whether you need planning permission for an extension and permitted development rights explained for how that's assessed.

The practical takeaway

• Most home extensions: current Part L rules apply, nothing has fundamentally changed for 2026
• New-build dwellings, annexes or self-contained units: the Future Homes Standard timetable is worth discussing at feasibility stage
• Heat pumps and solar PV are not required for existing homes or most extensions, whatever the headlines suggest

We factor current regulations into every extension project from the design stage, so you're not caught out by a requirement you didn't know applied.

Planning and Building Regulations rules are set nationally but applied locally, and they change from time to time. This article reflects general guidance correct at the time of publication — always confirm the current position for your specific property with your local planning authority or at gov.uk and the Planning Portal before relying on it.