Do I Need Planning Permission for Decking?

The planning rules for building a deck in your garden - when it counts as permitted development, height limits, and what triggers a planning application.

Decking is one of the most popular garden improvements in the UK. In most cases, you can build a deck without planning permission - but there is a critical height limit that catches many homeowners out, particularly on sloping gardens.

When Is Decking Permitted Development?

Garden decking is treated as a raised platform under the permitted development rules. It is permitted development provided:

The decking (together with any other raised platforms, including balconies) does not exceed 30 cm (300mm) above ground level
The total area of the decking, combined with all other outbuildings, extensions, and hard surfaces, does not cover more than 50% of the garden
The decking is not forward of the principal elevation facing a highway

The 300mm Rule

This is where most problems arise. The 300mm height is measured from the existing ground level at any point - not from the highest point of the garden. On a level garden, a standard deck built just above ground height easily stays within the limit. But on a sloping garden, the deck surface might be 300mm above ground at the top of the slope but 1 metre or more above ground at the bottom.

If any part of the decking exceeds 300mm above the natural ground level, the entire deck requires planning permission. This is a strict rule with no exceptions under PD.

When Do You Need Planning Permission?

You need planning permission if:

The deck exceeds 300mm above ground level at any point
It would result in more than 50% of the garden being covered by hard surfaces, outbuildings, and extensions
It is forward of the principal elevation facing a highway
Your property is a listed building
An Article 4 Direction has removed this PD right

In a conservation area, the standard decking PD rules still apply - there are no additional restrictions specific to conservation areas for decking at or below 300mm.

Raised Decking and Privacy

Raised decking (above 300mm) often raises concerns about overlooking and privacy. If you need planning permission for raised decking, the planning officer will consider the impact on neighbours - particularly whether the deck creates new sightlines into their garden or windows. You may be asked to add screening, privacy panels, or planting to mitigate overlooking.

Even if your deck is within PD limits, it is good practice to consider your neighbours' privacy. A deck that is technically permitted can still generate complaints if it creates an elevated viewing platform directly overlooking a neighbour's garden.

Building Regulations

Garden decking does not normally require building regulations approval. However, if the deck is attached to the house and structurally connected, or if it forms part of a means of escape from the house (e.g. providing access from a raised ground floor level), building regulations may be relevant. In practice, most freestanding garden decks do not need building regulations.

Drainage

If you are laying decking over a large area, consider the impact on drainage. Impermeable surfaces (including solid decking with no gaps) can increase surface water runoff. Under the permitted development rules, the construction of a hard surface at the front of a house must use permeable materials - but this rule does not apply to the rear garden.

Regardless of the rules, good drainage design avoids problems with waterlogging and can prevent disputes with neighbours about water runoff.

Tips

Measure ground level carefully - on sloping gardens, check the height at multiple points
Consider a split-level design - stepping the deck down a slope can keep all sections within 300mm
Talk to your neighbours - especially if the deck will be near a boundary
Use quality materials - composite decking lasts longer than timber and requires less maintenance
Apply for a Certificate of Lawfulness - useful at resale, particularly for larger decks