Do you need planning permission for decking?

What is the 30cm rule for decking?

The 30cm rule means garden decking is permitted development, with no planning application, as long as no part of it is more than 30cm above the ground. Government guidance calls anything higher a raised platform, and raised platforms need planning permission. It applies to timber and composite decking alike, in Somerset as across England.

The figure comes from the government's technical guidance on householder permitted development, which defines a raised platform as one with a height greater than 0.3 metres.

Thirty centimetres is not much. On a garden that falls away from the house, the far edge of a deck can sit well above the lawn. Sloping gardens are where most borderline cases come up, and the guidance sets out how height is measured on uneven ground. If your deck will sit near the limit, ask the council.

What is the 50% garden rule for decking?

The 50% rule says decking, together with every other extension, outbuilding and structure added to the house, must not cover more than half of the land around it. The original house itself is left out of the sum. A large deck in a garden that already has a garage, a shed and a rear extension can tip it over.

The government guidance says the 50% limit is worked out on the land around the house, excluding the area of the original house. "Original" means the house as it stood on 1 July 1948, or as it was built if it is newer. Anything added since counts.

• The new deck, measured on the ground it covers
• Rear and side extensions and conservatories added since the house was built
• Detached garages, sheds, summerhouses and workshops
• Other structures and enclosures in the garden, such as a raised platform you already have

Can you put decking in front of your house?

Not without planning permission. Permitted development for decking does not cover any land forward of the principal elevation, which is usually the front of the house facing the road. On a corner plot or an unusual layout, the principal elevation is not always obvious, so check with the council before building a deck at the side or front.

The technical guidance adds that the line carries on past the house, out to the side boundary. A deck by the front door, or across a side garden ahead of the house, needs an application.

Do listed buildings, conservation areas and the Mendip Hills change the rules?

Yes. In the grounds of a listed building no decking at all is permitted development. In conservation areas, Areas of Outstanding Natural Beauty such as the Mendip Hills, National Parks and World Heritage Sites, decking is not allowed at the side of the house, and there are limits on decking well away from the house.

The Mendip Hills, which rise behind Axbridge and Cheddar, are one of these protected areas. Many Somerset towns and villages also have conservation areas around their older streets. Somerset Council's advice is to check before starting work if you are not sure.

What about a raised deck next to a boundary?

A raised deck near a boundary is still covered by the 30cm rule: above that height it needs planning permission wherever it sits. Raised decks next to a fence are also where neighbour trouble starts, because standing on one can put you above the fence line and looking straight into the garden next door. Talk to your neighbours early.

People often plan a privacy screen along the edge of a raised deck. Fences have their own height rules, measured from the ground, and the guidance says decking does not count as ground level.

So a screen fixed on top of a raised deck is likely to be measured from the garden below, not from the boards: a 1.8 metre screen on a deck half a metre up could pass the 2 metre limit. Get the council's view first, and see our guide to fence height and boundary rules.

Do you need building regulations approval for decking?

If a deck needs planning permission, the Planning Portal says you should assume Building Regulations apply to it as well. That usually means a raised deck, which has to be safe to stand on and safe at the edges. If you are not sure whether your deck is covered, Somerset Council's building control team can tell you.

Planning and Building Regulations are separate. Planning is about whether the deck is allowed where it is; Building Regulations are about how it is built.

How do you check before you build a deck in Somerset?

Measure how high the deck will sit above the ground, add up what is already built in the garden, and find out whether the house is listed, in a conservation area or on the Mendip Hills. If it all sits inside the rules, go ahead. If anything is borderline, ask Somerset Council or apply for a lawful development certificate.

• Measure from the ground to the top of the planned deck at its highest point above the garden.
• Add up the footprint of every extension and outbuilding, plus the new deck, against the garden area.
• Check the deck stays behind the front of the house.
• Ask Somerset Council whether the house is listed, in a conservation area or covered by an Article 4 Direction.
• If you live in a flat or maisonette, or the deck is for a business, ask the council before anything else.
• If you want it in writing, apply for a lawful development certificate.

When you ask for quotes, tell each contractor the height and size you want and whether the house is listed or in a protected area, so everyone prices the same deck.