Do You Need Planning Permission for Decking? The 30cm Rule Explained

Nov 3

3 min read

Grey timber deck steps beside a white rendered raised planter

Most garden decking in England doesn't need planning permission. It's allowed under householder permitted development as long as the deck is no more than 30cm above the ground and, together with any extensions and outbuildings, covers no more than half of the garden. A raised deck, a deck on a listed building, or decking at a flat or maisonette will usually need an application.

The permitted development rules for decking

Under the permitted development rules explained by the Planning Portal, decking and other raised platforms are allowed without planning permission when:

Height: no part of the deck is more than 30cm above the ground
Area: the deck, together with other extensions, outbuildings and platforms, covers no more than 50% of the land around the original house
Not a balcony or veranda: raised platforms, balconies and verandas are not permitted development

Permitted development rights apply to houses. They don't apply to flats or maisonettes, and they can be removed or restricted for a property.

How is the 30cm measured?

The height is measured from the ground to the top of the platform. On a sloping garden this is where people get caught out: a deck that sits at ground level by the back door can be well over 30cm above the ground at its far edge. If any part of the deck is more than 30cm up, it isn't covered by permitted development, and planning permission is needed.

On a sloping site, the usual answers are to terrace the deck into two or more lower levels, cut the ground down under the deck, or apply for permission for the raised design.

When you'll need planning permission for decking

A raised deck more than 30cm above the ground at any point
A deck that, with other additions, covers more than half the garden
A listed building: listed building consent may be needed for works within its curtilage, even where planning isn't
A flat or maisonette: no householder permitted development rights
Where permitted development rights have been removed, for example by a condition on the original planning permission for a newer estate, or by an Article 4 direction
A deck forming a balcony or veranda, at any height

Conservation areas and other designated land don't automatically stop a low deck, but they do restrict what else you can do, so it's worth checking with your council if you're in one.

Raised decking and neighbours' privacy

The 30cm limit exists largely because of overlooking. A raised deck puts people's eye level above the fence line and looks straight into neighbouring gardens and windows. If you apply for a raised deck, the council will look at privacy, and screening (a solid screen or planting) on the sides facing neighbours often makes the difference.

Timber deck corner with a balustrade beside a hedge

Does decking need building regulations approval?

A garden deck generally doesn't need building regulations approval. It's still worth building to the standards that would apply: a sound frame, correct joist spacing, secure fixings and, on any deck high enough for a fall to cause injury, a proper balustrade. Approved Document K treats a drop of 600mm or more as the point where guarding is needed on stairs, landings and balconies in a house, and we use that as a sensible benchmark outdoors too.

A deck attached to the house also needs to sit below the damp proof course, with a gap to the wall so it doesn't trap water against the brickwork.

Can you check before you build?

Yes. If you're not sure whether a deck falls within permitted development, you can apply to the council for a Lawful Development Certificate. It isn't compulsory, but it gives written confirmation that the work is lawful, which can be useful when you sell. For anything clearly outside the rules, a householder planning application is the route; councils have a statutory eight weeks to decide one.

Designing within the rules

Most gardens can have a deck that sits within permitted development with a bit of planning: keep the platform low, step it down the slope rather than holding it up in the air, and balance the deck with lawn or planting so the half-garden limit isn't an issue. Our decking ideas include several designs that work on sloping plots without going over 30cm.

We design and build decking in Kettering and across Northamptonshire, and we check the planning position as part of every design. If a deck isn't the right answer for a slope, a terraced patio sometimes is, and our patios team can price that alternative. Get in touch to talk it through.