Stain on ceiling beneath bathroom - who would I ask to check it?

Hi Neil, You are right to be concerned as ceiling stains can indicate a number of problems which can be very costly to rectify. An experienced and qualified plumber would be the best person to speak to in a situation like this. I have dealt with a great numbers of problems very similar to your case and I can tell you that there is more than likely a slight leak from one of the pipes in the bathroom. The leak can be anything from a leaky bath trap, to a failing joint on the hot, cold or central heating pipes. It only takes a slight leak to cause discolouration and damage to the ceiling below over time. If the leak is rectified quickly you may get away with repainting the affected area below with no further problems, on the contrary if it is left as it is, the problem normally gets progressively worse and even when the leak is fixed the plastered damp area may crack which will require a section of the plaster to be cut out, re boarded, re plastered then painted. The cost to rectify a leak such as this can vary; if it can be accessed from above, for example by simply removing the bath panel then you are looking at few hours labour plus materials. However if it is not easily accessible then the the floor may need to be lifted (if it is tiled then they will need to be removed), or alternatively a section of the ceiling below may need to be cut out. I would normally investigate the problem in person to give an accurate diagnosis so I can only go by what you have said but I hope that my answer sheds some light on the situation. Kind regards, Chris Plumber and Heating Engineer Straight Flush Plumbing and Heating