Planning Your House Extension Budget in 2026

How to plan a full house extension budget: what drives cost, what the 2026 planning application fee covers, the other approval and professional costs to allow for, and what a good quotation should include. ## What does a house extension cost? There is no reliable single price per square metre that applies to every home.

The cost of an extension depends on its scope and specification: the size and shape of the space, ground conditions, structural work, glazing, heating, finishes and how much of the existing house is altered. Projects range from modest single-room additions to extensive renovations that include new kitchens and interiors.

The most dependable figure is a property-specific quotation based on a clear brief and, where needed, drawings and surveys. ## What affects the price? **Ground conditions** — clay soils, trees, drains and sloping sites can change the foundation design. **Specification** — glazing, roof design, heating, flooring, kitchens and finishes have a large effect on the overall budget.

**Structural complexity** — open-plan layouts, steelwork, building near boundaries or over drains add design and construction work. **Existing house** — how much of the current home is opened up, rewired or redecorated. ## Planning application fee From 1 April 2026, the statutory planning application fee in England for the enlargement, improvement or other alteration of a single dwellinghouse is **£548** ([GOV.

UK: Planning fees – annual indexation from 1 April 2026](https://assets.publishing.service.gov.uk/media/69a073bb07d7bff3604d6df6/Planning_fees_-_annual_indexation_from_1_April_2026.pdf)). This is only the application fee paid to the local planning authority. It is separate from the wider costs of obtaining approvals, such as design drawings, structural calculations, Building Regulations charges, any party wall costs and any submission or service charges from third parties.

Many extensions do not need a planning application at all because they fall within permitted development, so check what applies to your property and proposal. ## What a quote should include - Detailed specification of all works - Foundation design assumptions (with caveats for ground conditions) - All structural steelwork - Full electrical and plumbing first and second fix - Plastering and decoration - Building Control arrangements - Waste removal - Timeline with key milestones - Payment schedule linked to stages, not calendar dates --- ### What to do next If you are planning a house extension, EvoHome Improvements can help you organise the details, compare options and, where appropriate, connect the project with suitable independent installers or specialists.

EvoHome does not carry out the works directly. Start here: [/start](/start). You can also read more about how this service works at [/services/house-extensions](/services/house-extensions) and [/services/double-storey-extensions](/services/double-storey-extensions). ## Compare quotations on the same basis |…