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Roofs and flat roofs

Can a stain on a ceiling under the loft be the cold-water tank rather than the roof?

Yes. A tank, a ball valve or a pipe in the loft can wet the ceiling from above and copy a roof leak. The survey should say whether a tank sits over that stain and whether the timbers around it were wet. A roof sentence that never mentions the tank has not ruled the tank out.

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?

Lofts hold tanks, expansion vessels and pipes as well as rafters. Condensation on a tank, a failed valve and a split overflow all drip onto plasterboard. The stain is then circular or follows a pipe, not the line of a valley. A surveyor who entered the loft can see this if the tank is not buried in belongings. RICS surveys do not test the plumbing.

The Building Research Establishment’s warning about dripping roofs is about condensation in the void, which is a third possibility beside a tank and a hole in the covering. Ask which of the three the notes support. A plumber and a roofer answer different ones. Do not strip tiles because a tank overflow has stained a ceiling.

What should you ask your surveyor?

  • Does a tank or a pipe sit above the stain?
  • Was the loft boarded or stored so that you could not see the ceiling line?
  • Is the overflow piped outside, or did you not see one?

What are the typical next steps?

  1. Look in the loft, if it is safe, before you call a roofer. Do not step through the ceiling.
  2. Ask the seller when the tank last overflowed.
  3. If the survey could not see the tank, say so when you decide whether to investigate.

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

Is a loft tank a defect?

A tank is normal in many houses. The defect is a leak, a missing lid, or insulation that buries it so it freezes. The survey should say which.

Will removing the tank stop roof leaks?

Only if the tank was the source. It does nothing for a failed valley.

Sources