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External Door Building Regulations: The U-Value a New Front or Back Door Must Hit, Who Signs It Off, and the Rules for Flats

External door building regulations catch more people out than any other part of a refurbishment, because a new front or back door looks like a simple purchase. It is not: the Planning Portal treats a replacement external door, frame and all, as a controlled fitting under the Building Regulations. In England that means the new doorset must hit an energy standard, glazing in it must be safety glass, the threshold must not get worse, and someone has to certify the work. This page sets out each rule, who signs it off, and the extra rules that apply in flats and next to an integral garage.

Is a new external door covered by building regulations?

Yes, in most cases. The Building Regulations 2010 define a controlled fitting as one to which Parts G, H, J, L or P impose a requirement, and the Planning Portal is plain that an external window or door is a controlled fitting. What triggers the rules is replacing the whole unit: the door leaf and its fixed frame. Hanging a new leaf in the existing frame, fitting new locks, or replacing a cracked glass panel is a repair and does not bring the door under the regulations.

That applies to front doors, back doors, side doors, French doors and patio doors alike. Bifold and sliding doors follow the same logic, with an extra limit on glazing area in extensions; see our page on bifold doors building regulations.

The energy standard: a U-value of 1.4

Approved Document L, Volume 1, Table 4.2 sets the limiting values for new and replacement fittings in existing homes. For a door the whole doorset, not the glass alone, must reach a U-value of 1.4 W/m²K or better. Manufacturers may instead quote a Doorset Energy Rating (DSER): Band B or better for a mainly solid door, and Band C or better where more than 60% of the internal face is glazed.

Timber doors had a temporary concession at 1.8 W/m²K after the 2021 edition came in, but it ended on 14 June 2023, so a timber door now has to reach the same 1.4 as a composite or uPVC one. A new edition of Approved Document L takes effect on 24 March 2027; the limits for replacement doors in existing homes are not changing.

Ask the supplier for the whole-door U-value on paper. Most composite front doors sold in the UK are tested to well under 1.4. Older-style timber doors with large single panes are the ones that struggle, and some joinery firms now offer double-glazed or insulated-core versions of period designs to get there.

Safety glass

Approved Document K treats glass in a door between floor level and 1500mm above it as a critical location, along with glass in a side panel within 300mm of the door edge, up to the same height. In those zones the glass must be safety glass, toughened or laminated, and marked to show it, or be protected or of a small enough pane size to be safe. In a glazed front door with a side light, that is usually every pane. Our page on safety glass regulations explains the markings.

The threshold must not get worse

Part M asks for level or near-level access to new homes, and has done since 1999. When you replace the main entrance door of a home built since then, the Planning Portal warns that the threshold must stay level: a stepped sill or a raised weatherbar would make access worse than when the house was built, and the work would not comply. Older houses often have a step at the door already; the rule is that you do not make it harder to get in than it was.

Who signs it off

There are two routes.

1. A registered installer. If the fitter belongs to a competent person scheme for windows and doors, such as FENSA or Certass, they self-certify that the door complies and notify the council for you. You should receive a certificate afterwards. Keep it with the house papers: a buyer’s solicitor will ask for it.
2. Building control. If the installer is not registered, or you fit the door yourself, you need to apply to the council’s building control, or a registered building control approver, before the work starts, usually by building notice. They inspect and issue a completion certificate.

A door fitted with neither route has no certificate. That rarely matters until you sell, when it can hold up the sale or leave you needing a regularisation certificate or an indemnity policy.

Integral garages and fire doors

The door between a house and an integral garage is a fire door under Approved Document B, normally an FD30 doorset: the leaf, frame, intumescent strips and hinges working together to resist fire for 30 minutes. Swapping it for a standard internal or external door, or a glazed one, is a common mistake in garage-side utility rooms. Our page on whether you need fire doors covers what a certified doorset includes.

Flats: the front door is rarely just yours

A flat entrance door that opens onto a shared corridor or stair is part of the block’s fire strategy. It is normally a fire-resisting, self-closing doorset, and in most leases it belongs to the freeholder or is shared, so you need written consent before changing it. In blocks over 11 metres tall in England, the Fire Safety (England) Regulations 2022 require the responsible person to check flat entrance doors at least once a year, so an unauthorised replacement is likely to be found. See our page on the licence to alter for how consent works.

Security: Part Q only applies to new homes

Approved Document Q requires doors in new dwellings, including homes created by a change of use, to resist entry, usually by meeting PAS 24. It does not apply to replacing a door on an existing house. Buying a PAS 24 or Secured by Design door is still sensible, and some insurers ask about locks to BS 3621.

Planning permission

Building regulations and planning are separate. Replacing a house’s front or back door is usually permitted development and needs no planning application. Check first if the house is listed, as listed building consent is needed for almost any change; if it sits in a conservation area with an Article 4 direction covering doors; or if it is a flat, which has no householder permitted development rights. London councils regularly decide planning applications for replacement front doors in conservation areas.

A quick checklist before you order

• Get the whole-door U-value (1.4 or lower) or DSER band in writing.
• Confirm the glass in the door and side panels is marked safety glass.
• Ask whether the installer is FENSA or Certass registered; if not, apply to building control first.
• Keep the threshold level if the house is post-1999.
• Integral garage door: certified FD30 doorset only.
• Flat, listed building or Article 4 area: get consent before you order.

For the wider picture of what needs approval in a renovation, see our building regulations for renovations page, or go back to the Vertigo Interiors homepage.

Sources: Planning Portal: doors and windows, building regulations; Approved Document L; DLUHC circular letter, January 2022; Approved Document K; Building Regulations 2010, regulation 2.