Phase 1 · Planning & Permissions · Task 05 of 17
Prior Approval for a Larger Home Extension
The prior approval process for extending beyond standard PD limits (up to 6m or 8m). Covers the £249 fee, 42-day timeline, neighbour consultation, and what to do if refused.
Prior approval refusals have among the highest appeal success rates of any planning application type. The reason is consistent: councils apply tests they have no legal authority to use, and appeal inspectors correct those errors.
That matters for you because the Larger Home Extension scheme is one of the best tools available to homeowners who want to extend beyond standard permitted development depth limits. Up to 6 metres for a semi-detached or terraced house. Up to 8 metres for a detached house. No full planning application needed. But you do need prior approval, and understanding exactly how that process works is the difference between a smooth approval and months of unnecessary delay.
Do this first
This guide builds on the PD framework covered in Permitted Development Rules. If you haven't confirmed that your extension meets all other PD conditions (height, curtilage, materials), start there first.
When You Need Prior Approval
Standard permitted development lets you extend 3 metres from the rear wall of a semi-detached or terraced house, or 4 metres from a detached house, without telling anyone.
Go beyond those depths and you enter the prior approval regime. The maximum you can reach through this route is 6 metres (semi/terraced) or 8 metres (detached). Beyond that, you need a full householder planning application.
All the other PD conditions still apply. Your extension must be single-storey. Maximum height 4 metres. Eaves no higher than 3 metres if within 2 metres of a boundary. Materials that are visually similar to the existing house. Total extensions (including any previous ones) covering no more than 50% of the curtilage.
The prior approval process adds one extra test on top: the impact on the amenity of adjoining properties. That's it. One test.
42 days
The council has 42 days to decide your prior approval application. If they don't issue a decision in that time (and haven't agreed a written extension with you), your extension is deemed approved automatically.
What It Costs
The council fee for a prior approval application is £249. If you submit through the Planning Portal, they add a service charge of £91 on top, bringing the total to the cost of both fees combined.
That's cheaper than a full householder planning application at £548, and the assessment is far more restricted. The council has fewer grounds to refuse.
Tip
Some councils let you submit prior approval applications directly, bypassing the Planning Portal service charge. Check your council's planning pages before assuming you must use the Portal.
What this guide covers
- 01What to Submit
- 02The 42-Day Timeline
- 03What Councils Can (and Cannot) Assess
- 04The 45-Degree Rule
- 05Common Refusal Reasons (and Why Many Are Wrong)
- 06How to Appeal
- 07Before You Submit: Practical Tips
- 08Who Cannot Use This Route
- 09The Bottom Line
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