Extensions Without Planning Permission in Lancashire: The Rules

What permitted development allows

Permitted development is a set of national rules that lets you extend a house without applying to the council, as long as you stay inside fixed size limits. In Tarleton the council is West Lancashire Borough Council. The limits are measured from the original house, meaning the house as first built or as it stood in 1948, so any earlier extension counts against your allowance.

The main limits for a typical house are:

• Single-storey rear extension: up to 3 metres deep on a semi or terrace, 4 metres on a detached house
• Maximum height of 4 metres, with eaves no higher than 3 metres if within 2 metres of a boundary
• Side extension: single storey only, and no wider than half the width of the original house
• Two-storey rear extension: up to 3 metres deep and at least 7 metres from the rear boundary
• Extensions and outbuildings together must not cover more than half the land around the original house
• Nothing forward of the front wall, and materials that look similar to the existing house

Larger rear extensions and prior approval

If 3 or 4 metres is not enough, you can go up to 6 metres on a semi or terrace and 8 metres on a detached house, single storey only. This is not automatic. You have to notify the council, which then consults your adjoining neighbours and has 42 days to decide. If a neighbour objects, the council assesses the effect on their light and outlook and can refuse.

It is quicker and cheaper than a full application, but allow a couple of months in your programme before a builder can start.

When you will need planning permission

Some properties have reduced rights or none at all. Check these before you spend money on drawings:

• Flats and maisonettes have no permitted development rights for extensions
• Listed buildings need listed building consent for almost any alteration
• In a conservation area, side extensions and two-storey rear extensions need permission
• Newer estates often had permitted development rights removed as a condition of the original planning approval
• Barn conversions and other changes of use usually have rights removed too
• Wraparound extensions that join a side and rear extension usually fall outside the rules

Local points to check around Tarleton

Tarleton, Hesketh Bank and the surrounding villages sit on flat, low-lying land close to the River Douglas, and that affects extensions in practical ways. Parts of the area fall within flood risk zones, which can mean raised floor levels or flood-resilient construction. Much of the ground is soft mossland, so standard strip foundations are not always suitable. Building control may ask for deeper trenches, a raft or piles, and that can add several thousand pounds to the groundworks.

If your extension is within 3 metres of a public sewer, you will need a build over agreement from United Utilities. Much of the land around the village is Green Belt. Permitted development still applies there, but anything needing a full application will be judged more strictly on size.

What you still need without planning permission

Skipping planning permission does not mean skipping the paperwork. Every extension needs building regulations approval, covering foundations, structure, insulation, drainage, fire safety and electrics. If you are building on or near a shared boundary, the Party Wall Act requires written notice to your neighbour, normally at least one or two months before work starts.

We would also recommend a Lawful Development Certificate from the council. It is optional and costs a few hundred pounds, but it gives you written proof that the extension was lawful, which solicitors often ask for when you sell. As a rough guide, a single-storey extension in Lancashire commonly costs between £1,800 and £2,800 per square metre, depending on ground conditions, glazing, and the kitchen or bathroom going inside it.