What You Can Build Under Permitted Development?

Permitted Development (often shortened to PD) is one of the most useful, and misunderstood, parts of the UK planning system.

For homeowners across Greater Manchester and Cheshire, it can allow you to extend, convert or alter your home without applying for full planning permission. Done right, it can save time, reduce costs, and remove a lot of uncertainty early on.

Done wrong, it can lead to enforcement issues, expensive redesigns, or projects being delayed halfway through construction.

In this guide, I’ll explain what you can build under Permitted Development, where the limits sit, and when PD does not apply — all in plain English, based on how the rules are actually applied in practice.

What Is Permitted Development?

Permitted Development rights are a set of national planning permissions granted by the government. They allow certain types of building work to go ahead without submitting a full planning application to the local council.

Instead of seeking planning permission, you must ensure your proposal:

• Meets specific size, height and location rules

• Uses appropriate materials

• Does not conflict with local restrictions (such as conservation areas)

In many cases, homeowners still apply for a Lawful Development Certificate (LDC) to formally confirm that the works are permitted — something we regularly advise on at Nada Architects for peace of mind and future resale.

Permitted Development applies to houses, not flats or maisonettes, and works differently depending on:

• Whether your property is detached, semi-detached or terraced

• Whether it’s in a conservation area

• Whether previous extensions have already used up PD allowances

What You Can Build Under Permitted Development

Below is a practical overview of the most common works allowed under PD. These are the projects we’re most often asked about by homeowners at the early feasibility stage.

Rear Extensions

Single-storey rear extensions are one of the most popular uses of PD.

You can typically extend:

• Up to 8 metres from the original rear wall on a detached house

• Up to 6 metres on a semi-detached or terraced house

Height limits apply:

• Maximum 4 metres for a single-storey extension

• 3 metres if it’s within 2 metres of a boundary

If you want to use the larger extension allowances, you may need to go through the Prior Approval process, where the council consults neighbours on impact.

This is where early input from an architect helps avoid neighbour objections and design issues. Many of these projects start with a Feasibility Study to confirm what’s realistically achievable.

Loft Conversions

Most loft conversions fall under Permitted Development, provided the roof shape is respected.

Typical allowances:

• 40 cubic metres for terraced houses

• 50 cubic metres for detached and semi-detached houses

You can usually include:

• Rear dormers

• Rooflights to the front roof slope (if they’re flush)

Restrictions include:

• No extensions beyond the existing roof plane at the front

• No raised ridge height

• Materials must be similar in appearance to the existing roof

If designed carefully, PD loft conversions can add significant space without the delay of planning permission.

See our dedicated Loft Conversions service page for more detail on layout and design options.

Side Extensions (Limited)

Side extensions are more restricted under PD.

You can build:

• A single-storey side extension only

• Maximum width of half the original house

• Maximum height of 4 metres

Two-storey side extensions always require planning permission, regardless of size.

Outbuildings and Garden Rooms

Permitted Development allows for many garden structures, including:

• Home offices

• Gyms

• Studios

• Storage buildings

Key rules:

• Must be incidental to the main house (not self-contained living)

• Must not cover more than 50% of the garden area

• Maximum height of 2.5 metres near boundaries

Outbuildings are often straightforward, but positioning and use are critical. A “garden room” that functions like a separate dwelling will usually require planning permission.

Internal Alterations

Internal works do not require planning permission, provided you:

• Do not alter the building’s external appearance

• Are not working on a listed building

This includes:

• Reconfiguring layouts

• Removing non-structural walls

• Internal stair changes

Building Regulations approval is still required, even if planning is not.

Changes to Roofs and Openings

Permitted Development often covers:

• Rooflights

• New windows

• New doors

As long as:

• They do not project excessively

• They are not on a protected elevation in a conservation area

• They do not create privacy issues (e.g. side-facing windows above ground floor often need obscure glazing)