Leasehold

One loft tank appears to feed this flat and the neighbour's. Why is that a title and plumbing question, not a roof rating?

Because one loft tank that appears to feed this flat and the neighbour's is a shared-supply and title question, not a rating of the roof. The survey can note a tank and pipes that seem to serve two homes. It cannot say who owns the tank, who must maintain it, or whether the neighbour has a right to it. Those points sit with the lease and the solicitor. The roof covering is a different element. Do not turn a shared cistern into a roof defect. Ask the solicitor about the tank, and a plumber about the pipework, as separate questions.

Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.

What is the fuller explanation?

A loft tank that straddles two flats may be common plumbing, a trespass, or a service reserved in the leases. Looking at pipes that leave the cistern toward two dwellings supports the appearance of a shared feed. It does not read the lease, and it does not rate the slates or the felt. A roof rating belongs to the roof. Ownership, repair duty and the right to draw water are legal and practical questions about the tank.

Ask the solicitor to check the lease and the plan for this tank, and ask who is responsible if it leaks or needs replacing. Ask a plumber only about the pipes and valves you can see, not about title. Do not cap the neighbour's feed on a viewing. If the survey mentioned the roof separately, leave that paragraph on the roof. The shared tank stays a plumbing and title issue until the papers and, if needed, a plumber have answered their own parts of it.

What should you ask your surveyor?

What did you see that suggests the one tank feeds both flats?
Where is the tank relative to the party line, if that was visible?
Are you keeping this note off any roof-covering rating?

What are the typical next steps?

Ask the solicitor who owns the tank and who must maintain it.
Ask a plumber about the shared pipes only as pipework.
Do not treat the tank as a roof rating.

Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.

Also asked about this

If the tank leaks into the loft, is that automatically a roof failure?

No. A leaking tank is plumbing. It can wet the loft, but it is not the same defect as a failed roof covering, and the title question remains.

Can you isolate the neighbour and keep the tank?

Do not try. Who may draw from it is a lease question for the solicitor. Capping a pipe on a viewing would not settle the title.