Alterations and repair or maintenance - case law and agreements: treatments and processes
Treatments to the exterior of a building are normally designed to rectify an existing problem or to prevent future ones. As such they are works of repair or maintenance.
This view was upheld in B Cheeseman (VTD 5133): Strength and stability was restored to an unstable wall by injecting a chemical and then a catalyst, which caused the chemicals to react and set very hard. The Tribunal held it was repair or maintenance.