My neighbour has built a house under my BT line. The line is now extremely tight and stretched over the roof of the house. Is there a maximum height restriction that a cable should be above a house?
You need to contact Openreach rather than BT, try 0800 023 2023. Not sure if there is a minimum height but if the line is actually touching the roof of the house it will chafe through in very short time. Your neighbour should have contacted Openreach before starting work.
Since your line was in place before the house was built then that fact should have been incorporated into any planning consent given. As it is now stretched over the house it is likely there has been some form of breach of the planning consent eg the line should have been moved prior to the build commencing. You should check with the planning department to see what should have happened and what redress you have.
Your neighbour should of contacted Openreach prior to building, they have info here which addresses work that impacts Openreach network, from what I've heard it's not cheap either.
What happens if I alter your network in any way or don't contact you?
If you don't contact us and an incident occurs because you or your contractors have altered, interfered or tampered with our network, you will be held responsible – potential consequences include compensation claims, investigation by the Health and Safety Executive (HSE) and possible criminal charges.
If there is any Openreach equipment on a property you'll be working on, we're the only people who can move it for you. If you don't contact us and make any alterations, remove or replace fixings, remove drop-wires or lead-ins (temporarily or permanently) or do anything which adversely affects our network this would be classed as trespass and we would take appropriate action against any third party who trespasses on our network.