Yes. Most policies require you to notify your insurer before undertaking significant building work. Failing to do so can invalidate your policy, leaving you responsible for all costs if something goes wrong. You should notify your insurer about structural renovations (rewiring, re-roofing), layout changes (extensions), and conversions (loft, cellar, garage). Minor cosmetic works like repainting may not need notification, but it's always worth checking with your provider first.