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Decking Building Regulations: A 2026 Guide to Part K and Permitted Development

Bhavesh Ramburn

When does a deck need Building Regulations approval?

A decking structure (also called a deck, raised platform, or timber terrace) may need Building Regulations approval depending on its height, location, and intended use. The Building Regulations are the national technical standards for the design, construction, and alteration of buildings, made under the Building Act 1984 and set out in the Building Regulations 2010 (SI 2010/2214).

The key threshold is the height of the decking above ground level. A deck that is:

  • Less than 300mm (1 foot) above ground level is generally exempt from Building Regulations approval, as it is treated as part of the ground surface.
  • Between 300mm and 600mm above ground level may require approval under Part K (Protection from falling, impact and collision) of the Building Regulations, depending on the specific design and location.
  • More than 600mm (2 feet) above ground level will almost always require a Full Plans application under the Building Regulations.

In addition, any deck that is attached to the house is generally treated as part of the house for the purposes of the Building Regulations and will require approval regardless of its height.

The technical standards are set out in the Approved Documents published by the Department for Levelling Up, Housing and Communities.

For the broader context on the Building Regulations regime, see our Building Regulations UK guide and our Building Control in the UK guide.

Part K requirements for raised decking

Where Building Regulations approval is required for a raised deck, the principal applicable Approved Document is Part K (Protection from falling, impact and collision). The Part K requirements for a raised deck are:

  • Guarding — any deck that is more than 600mm above ground level must have a protective guard (balustrade or railing) around any open side. The guard must be at least 1,100mm (1.1 metres) high. Where the deck is more than 12 metres above ground level, the guard must be at least 1,200mm high.
  • Structural stability — the deck and the guard must be structurally adequate. Most raised decks are timber-framed, with the posts set in concrete footings and the joists spanning between the posts. The structural design must comply with Part A (Structure) of the Building Regulations.
  • Resistance to loads — the deck must be able to resist the loads set out in Part A, including the dead load (the weight of the deck itself) and the imposed load (people, furniture, etc.). For domestic decks, the imposed load is typically 1.5 kN/m².
  • Resistance to moisture — the timber must be either naturally durable (e.g. oak, cedar) or pressure-treated to resist rot and insect attack. The fixings must be corrosion-resistant (galvanised or stainless steel).

The Building Control inspector will check the construction details at the post-installation inspection to confirm that the deck meets the required standards.

Building Regulations exemptions for decking

A deck is exempt from Building Regulations approval in the following circumstances:

  • The deck is less than 300mm above ground level at any point.
  • The deck is fully detached from any building and is used only for incidental purposes (e.g. a low-level patio area).
  • The deck is part of a Permitted Development outbuilding (e.g. a veranda attached to a summerhouse) and falls within the 15m² Schedule 2 exemption. For more on this, see our Building Regulations for outbuildings over 30m² guide.

Even where the deck is exempt from Building Regulations, the planning permission regime under the Town and Country Planning Act 1990 may still apply. A deck can be a “development” within the meaning of planning law and may require planning permission if it is more than 200 square metres in area or within 20 metres of the house. For most domestic decks, planning permission is not required, but it is worth checking with your local authority.

For the planning-permission side, see our householder planning permission guide and our Permitted Development Rights in 2026 guide.

Permitted Development rules for decking

A low-level deck (less than 300mm above ground level) is generally Permitted Development under the Town and Country Planning (General Permitted Development) (England) Order 2015 (the GPDO), provided:

  • The deck is in the curtilage of the house.
  • The deck, together with any other outbuildings and extensions, does not cover more than 50% of the curtilage of the original house.
  • The deck is not in front of the principal elevation of the house (unless it is less than 300mm above ground level).
  • The deck is not in a Conservation Area where the LPA has removed Permitted Development rights via an Article 4 Direction.

A raised deck (more than 300mm above ground level) may still be Permitted Development, but it is more likely to be considered an “extension” to the dwelling and subject to the same Permitted Development limits as an extension (no more than 50% of the curtilage, not in front of the principal elevation, etc.).

If a raised deck exceeds the Permitted Development limits — for example, because it is in front of the principal elevation, or because it covers more than 50% of the curtilage — a full planning application is required.

For a worked example of how Permitted Development rules apply to outbuildings and similar structures, see our Building Regulations for outbuildings over 30m² guide.

How to apply for Building Regulations approval for a raised deck

Where Building Regulations approval is required for a raised deck, the application process is the same as for any other Building Regulations project. The two routes are:

  1. Full Plans application. Submit detailed drawings and specifications to the Building Control body before work starts. The drawings are checked against the Building Regulations and either approved or returned with comments. The Building Control body will check the structural design, the guarding specification, and the Part K requirements.
  2. Building Notice. A shorter, simpler route for smaller works. You give the Building Control body at least 48 hours’ notice of work starting.

For most raised decks, the Full Plans application is the safer option because it gives certainty on the design before construction begins. A typical application fee for a raised deck is £200–£500.

The application must include:

  • A location plan at 1:1250 or 1:2500 scale, showing the deck outlined in red.
  • A block plan at 1:200 or 1:500 scale, showing the deck, the house, and the relevant boundaries.
  • Construction drawings at 1:50 or 1:100 scale, showing the post locations, joist sizes, decking board specification, and guard details.
  • Structural calculations if the deck is more than 600mm above ground level or if the spans are large.

For the broader application process, see our Building Control Application guide and our Building Notice guide.

The Completion Certificate for a raised deck

On satisfactory completion of the work, the Building Control body issues a Completion Certificate. For a raised deck, the Completion Certificate is the proof that the work complied with the Building Regulations at the time of construction.

The Completion Certificate is required when the property is sold, and may be requested by the buyer’s solicitor. Without it, the buyer’s solicitor may:

  • Insist on a discounted purchase price to cover the cost of retrospective certification.
  • Insist on the deck being inspected before exchange of contracts.
  • In rare cases, withdraw from the transaction.

For more on the Completion Certificate, see our Building Regulations Compliance Certificate guide.

Next steps and resources

Editorial note. This article is for guidance only and does not constitute regulated advice. The Building Regulations requirements for a raised deck depend on the height, location, and structural design. For project-specific questions, consult a Building Control inspector or a chartered surveyor registered with RICS.