Repair vs alteration to listed buildings

The short answer

Repair preserves the building; alteration changes it. Repair does not need consent; alteration does. The line is fact-specific, the burden of proof sits with the owner, and a poorly documented "repair" specification is one of the most common routes to an enforcement notice in central London. When in doubt, get a written officer view or commission a brief heritage opinion before instructing the contractor.

What the statute actually says

Section 7 of the Planning (Listed Buildings and Conservation Areas) Act 1990 prohibits "the execution of any works for the demolition of a listed building or for its alteration or extension in any manner which would affect its character as a building of special architectural or historic interest" without consent. Repair is conspicuously absent from that list. Section 9 makes unauthorised works a criminal offence.

The Shimizu test

Shimizu (UK) Ltd v Westminster City Council [1997] UKHL 4 is the leading authority. The House of Lords held that "demolition" means demolition of the building, not demolition of a part, and that works falling short of demolition may still amount to alteration. The implication for repair: works of repair which preserve, rather than alter, the building are outside section 7 even if they involve some replacement of fabric.

The threshold is practical, not absolute. Splice repair to a rotten sash section is repair. Full sash replacement, even in identical timber to identical profiles, is alteration. Replacement of three broken slates is repair. Re-roofing the entire slope is alteration.

Worked examples of the line

• Lime mortar repointing. Like-for-like with matched mortar mix is repair. Cement repointing of a lime-built wall is alteration (and damages the wall).
• Floor boards. Refixing loose boards and replacing one or two rotten boards with reclaimed equivalents is repair. Lifting and replacing a whole room of historic boards is alteration.
• Plaster. Patching damaged plaster with lime is repair. Stripping all plaster and re-skimming with gypsum is alteration.
• Iron railings. Repainting in matching colour is repair. Replacing missing finials with new castings to the original pattern is borderline; a single missing finial is usually treated as repair, a programme of replacements as alteration.

Materials: like-for-like in practice

Like-for-like means matching the material, the section, the profile, the detail and the fixing method. A timber sash repaired with a steel splice is not like-for-like. A lime mortar repointing job using ordinary Portland cement is not like-for-like, and is positively damaging.

Documenting repair to defend it

1. Photograph the existing fabric before any work, with a scale rule visible.
2. Write a one-page method statement naming the materials, the contractor and the extent of the work.
3. Keep the supplier invoices showing the materials specified.
4. Photograph the completed work.
5. Keep the file for the life of your ownership of the building.

Enforcement: why the distinction matters

Unauthorised works to a listed building are a criminal offence under section 9, with unlimited fines on conviction. There is no four-year or ten-year cut-off for enforcement (unlike planning). The defence of repair is available, but it is a defence: the burden of evidencing it rests on the defendant. A clean repair file makes that defence; an absent file usually loses it. See the Historic England guidance on listed buildings for the formal position.