Leak in Bedroom bay window ceiling and under window walls wet

You could have two separate issues here .... or just the one (the bay roof) which is contributing to the other. Difficult to assess the second condition with water under the window without seeing the situation (and unfortunately it is not possible for photos to be displayed on this forum) An Independent Damp Surveyor would be able to advise accordingly and they are not costly (in comparison to paying out for unnecessary work) However, I would suggest employing the services of a competent roofer to tackle your 'known' issue with the bay roof. If you check out the roofer's profiles beforehand (on MyBuilder, for instance), you may be able to find a roofer that deals with specific damp issues also. You may find that sorting out this bay window roof cures the other problem. Possible other causes: condensation (especially winter months) which would need a moisture management strategy - ventilation / heating etc; defective sealant around window; defective window construction / installation; defective pointing / rendering; defective or blocked gutters / downspouts. It's difficult to assess a problem without a more visual context but hope this post gives you some indications Regards, Chris

Sounds like you need to get the opinion of a builder and a damp specialist

Either a builder or roofer

Hi, I agree with the previous answer with regards to repairing the known causes of damp first (gutter and roofing). On interior side: The damp plaster should be removed back to brick and a 3x coat lime plaster system applied. After the plaster has dried and cured it should be painted with a breathable paint that does not contain plastic.