Fitting a sliding patio door

A sliding patio door is mostly glass. It opens a room onto the garden and lets in a lot of light. Two sets of rules cover that glass, one on safety and one on heat loss. This page sets out what a new door must meet in England, and who signs it off.

A new door is a controlled fitting

The Planning Portal says an external window or door is a "controlled fitting" under the Building Regulations. Building regulations have applied to all replacement glazing since 1 April 2002.

You can use an installer registered with a competent person scheme. The installer can then carry out the work without involving local authority building control, and you receive a certificate when it is complete. With an unregistered installer, or doing it yourself, you ask a building control body for approval. That is your council or a registered building control approver.

Approved Document L says a controlled fitting is the entire unit of a door, including the frame. Replacing only the glass, or a door in its existing frame, is not providing a controlled fitting.

Safety glass

Approved Document K covers glass in critical locations, which its Diagram 5.1 shows. There, the glass should break safely, resist impact, be in small panes, or be permanently protected.

The Planning Portal's summary of those locations includes "any glazed door up to 1500mm from floor level". It also includes any side panel up to 300mm from the edge of a door, up to 1500mm from floor level.

Heat loss

Approved Document L, Volume 1, covers new and replacement doors in existing homes. Its 2021 edition, incorporating the 2023 amendments, sets limiting values in Table 4.2. For doors with more than 60% of the internal face glazed, the limit is a U-value of 1.4 W/(m²·K), or a Doorset Energy Rating of Band C minimum. A U-value measures how much heat passes through the door, and a lower one loses less heat.

A 2026 edition takes effect on 24 March 2027 for building work in England that is not connected with higher-risk building work. Its Table 3.2 gives the same limit for these doors.

Planning permission

The Planning Portal says you do not usually need to apply for planning permission for new doors of a similar appearance to those used in the construction of the house. A council can withdraw that right with an Article 4 Direction.

A leaseholder may first need permission from the landlord or management company. In a listed building, you will need listed building consent for any significant works, inside or out. In all these cases, the Planning Portal advises checking with your local planning authority before work starts.

Sliding doors at work

In buildings other than homes, requirement K6 of the Building Regulations covers doors and gates that slide. Approved Document K says a sliding door should have a stop or other effective means to prevent it coming off the end of the track. It should also have a retaining rail to prevent it falling if the suspension system fails or the rollers leave the track.

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