Technical Booklet M Physical Infrastructure for High Speed Communications Networks·Page 11·1.7
Major Renovation Works Trigger for Existing Buildings
Part M requirements for high-speed communications networks apply to existing buildings only when major renovation works involving modification of significant portions of the in-building physical infrastructure are undertaken, typically requiring a building regulations application.
In relation to existing buildings, Part M requirements only apply where major renovation works are to take place. These works should involve the modification of a significant part, or all, of the entire in-building physical infrastructure and should be sufficient to normally require a building regulations application for requirements other than Part M of the Building Regulations.
Source — /Users/richardhill/Documents/planning-arch-project/data/documents/regional/Technical Booklet M - Physical Infrastructure for High-Speed Communications Networks.pdf