Do You Need Planning Permission for an Extension?

Not every extension needs planning permission, but every extension needs a building warrant. Getting those two things straight is the difference between a smooth project and an expensive surprise. Here is how it works in Scotland.

This is the single question we are asked most often by homeowners planning a home extension in Aberdeen. The honest answer is that it depends, and that the rules trip people up because there are really two separate approvals at play, not one. Many smaller extensions fall under what is called permitted development and never need a planning application at all. Almost every extension, however, still needs a building warrant before work can start. Confusing the two is the most common mistake we see.

The three approvals, kept separate

Before we get into limits and measurements, it helps to name the three things that can be in play. Keeping them apart is half the battle.

1. Permitted development. A set of rights that let you build certain extensions without applying for planning permission. If your project sits within the limits, you have the right to go ahead on the planning side.
2. Planning permission. A formal application to your local council when your extension falls outside permitted development. The council assesses the size, siting and impact on neighbours and the streetscape.
3. The building warrant. A separate approval covering structure, fire safety, insulation, drainage and energy. In Scotland this comes from Aberdeen City Council or Aberdeenshire Council, depending on where you live, and an extension needs one whether or not it needed planning permission.

Notice that the warrant sits on its own. You can have a small rear extension that needs no planning permission whatsoever and still, quite correctly, requires a building warrant. The two systems answer different questions.

What permitted development covers for extensions

Permitted development rights for house extensions in Scotland are set out in national planning rules. They allow many homeowners to extend without a planning application, provided the work stays within defined limits. The rules are detailed and clause-specific, so rather than quoting exact figures we would rather you misread, here are the factors that decide whether your extension qualifies.

Single-storey rear extensions

Rear extensions are the most likely to fall within permitted development. How far you can project from the original rear wall, and how tall the extension can be, are both capped, and the allowance is generally more generous for a detached house than for an attached one. A flat-roofed single-storey addition that stays modest in depth and height is the classic permitted development extension.

Proximity to boundaries

How close your extension sits to a boundary matters, and an extension near a boundary usually faces a tighter height limit. Building right up to a shared boundary, or beyond certain heights close to it, is one of the most common reasons a project tips into needing planning permission.

Proportion of garden ground

Permitted development is designed to protect open space, so there is a limit on how much of your garden ground the extensions can cover. If your proposal would swallow too large a share of the original curtilage, it falls outside the rights and a planning application is needed.

Front and side extensions

Extensions to the front of a house, facing the road, are treated far more strictly than rear ones and very often need planning permission. Side extensions sit somewhere in between and depend heavily on width, height and how close they come to the boundary. Neither is as freely permitted as a modest rear addition.

When permitted development does not apply

Some homes have reduced permitted development rights, or none at all, for extensions. If any of the following describe your property, treat a planning application as the likely starting point rather than the exception.

• Flats and tenements. Permitted development rights for extensions apply to houses, not to flats or tenement properties. If you live in a flat, an extension will generally need a full planning application.
• Conservation areas. Aberdeen has several conservation areas, and ground-floor extension rights are restricted or removed within them to protect the character of the street. A modest rear extension that would be permitted elsewhere may need permission here.
• Listed buildings. Listed status brings its own consent regime on top of planning, and changes are assessed far more closely.
• Homes where rights have been removed. On some newer developments, permitted development rights are withdrawn by a planning condition when the estate is built, so it is always worth checking.

Because these factors hinge on your exact address and the specifics of your home, they are something a surveyor or architect confirms rather than something you can settle from a guide. We check this as a matter of course before any drawings are produced.

The building warrant: required either way

This is the part homeowners most often overlook. Even when your extension is fully within permitted development and needs no planning permission, it still needs a building warrant. The warrant is how the council confirms the work meets the Scottish building standards for structure, fire safety, insulation, ventilation and drainage.

The process runs in parallel with, or after, any planning matters. Drawings and structural calculations are submitted to building standards at Aberdeen City or Aberdeenshire Council, the warrant is granted, the work is built and inspected, and a completion certificate is issued at the end. That certificate matters well beyond the build itself, because it is the document a solicitor and a future buyer will want to see when you eventually sell. Building without a warrant, or without closing one out, can create real problems at sale.

Planning and warrant at a glance

The pattern is clear: planning permission depends on the size, position and location of your extension, while the building warrant column reads the same all the way down. Where you sit in the planning column is exactly what a survey settles.

How this affects your budget and timeline

Knowing which route you are on matters because it shapes both cost and programme. A permitted development extension can move faster on the planning side, while a full application adds a determination period before work can begin. Either way, time should be built into your plan rather than assumed away. The work itself is the larger cost: a typical single-storey extension starts from around £45,000, with extensions costed at roughly £2,500 per square metre, and a double-storey extension starting from around £75,000.