Do I Need Planning Permission for a House Extension in Altrincham?

One of the most common questions homeowners ask us at Tatton Projects is:“Do I need planning permission for my extension?”

The answer depends on the size, type, and location of your extension. In this guide, we’ll break down the rules in Altrincham and the wider Cheshire area, explain what “permitted development” means, and help you avoid costly mistakes.

When You Don’t Need Planning Permission

In many cases, extensions fall under Permitted Development Rights (PD), meaning you don’t need full planning permission. Common examples include:

• A single-storey rear extension that does not extend beyond 3m (terrace/semis) or 4m (detached homes).

• Extensions that are not higher than the existing roof.

• Materials that are similar in appearance to the existing house.

• Width restrictions on side extensions.

👉 Always check with your local council, as rules can vary and permitted development rights sometimes don’t apply (e.g. in conservation areas).

When You Do Need Planning Permission

You’ll usually need planning permission if:

• The extension is taller than the highest part of the roof.

• You’re building a two-storey extension closer than 7m to the rear boundary.

• The build takes up more than 50% of the original land around the house.

• You’re in a conservation area or your property is listed (common in some parts of Cheshire).

• The design is significantly different from the existing house.

Building Regulations Approval (Separate from Planning)

Even if planning permission isn’t required, you will always need Building Regulations approval to ensure the extension is safe, energy-efficient, and compliant. This covers things like:

• Structural strength

• Fire safety

• Insulation and energy performance

• Drainage and plumbing

Costs & Timelines

• Planning application fee (England): ~£206 (as of 2025).

• Timeline: 8–10 weeks for a decision from Trafford Council (Altrincham’s local authority).

• Delays: Possible if your home is in a conservation area or if neighbours raise objections.

Why Work with Tatton Projects

At Tatton Projects, we handle planning permission and building regulations as part of our project management service. We’ll:

• Advise if your extension qualifies under permitted development.

• Prepare drawings and submit applications where needed.

• Manage the process with Trafford Council on your behalf.

• Ensure compliance with building regulations throughout the build.

This saves you time, stress, and potential costly mistakes.

Final Thoughts

Whether you need planning permission for your extension in Altrincham depends on your property and your plans. While many small extensions fall under permitted development, it’s always worth checking before you start building.

👉 Get in touch with Tatton Projects today — we’ll review your project and guide you through the process from start to finish.

New build completed in Mobberley