Incorrect Tiles Fitted

What I'd do: 1. Get the independent builder's findings in writing. Ask for a short report that states the roof pitch, the tile type, the manufacturer's minimum pitch, and the leak locations. Photos help too. 2. Check your paperwork. Look at your contract or quote, any warranty or insurance-backed guarantee, and the Building Control completion certificate. 3. Write to the builder formally. Set out the fault, include the report, and ask them to put it right within a reasonable time, e.g. 14–28 days. Keep everything in writing. 4. If they refuse or don't reply, get quotes for the fix and consider the small claims court or legal advice. Under the Consumer Rights Act, work must be done with reasonable care and skill.

From the information provided, I would definitely recommend getting the roof inspected by a competent roofing contractor before assuming that the cracked tiles are the cause of the leaks. A roof pitch of 16.4° is relatively low, so the exact tile specification, headlap, batten gauge, underlay and detailing around the Velux windows are all important. The manufacturer’s installation requirements need to be checked against how the roof was actually constructed. If the tiles fitted are not approved for the pitch and installation method used, and that is contributing to the water ingress, there may be grounds to go back to the original builder. The fact that the extension was built in 2021 does not automatically mean you have no recourse, although any legal claim would depend on the contract, evidence of defective workmanship/design and the applicable limitation period. For example, ordinary contractual claims are generally subject to a six-year limitation period in England and Wales. (Legislation.gov.uk⁠) I would suggest getting an independent roofer to provide a written report confirming: * the actual roof pitch; * the exact tile manufacturer and product; * the manufacturer’s minimum pitch for that product; * the required headlap and whether it has been achieved; * the underlay and batten arrangement; * the detailing around the Velux windows; and * the likely cause of the water ingress. With a written report establishing that the roof has been incorrectly specified or constructed, you would then have much stronger evidence to approach the original builder. As a roofing contractor, I would be happy to inspect the roof and give you an independent opinion on the roofing installation and the likely cause of the leaks.

Was there no plans for the extension stating the materials to be used, if not it's basically just your word against his, am a bit surprised building control never said anything at the time