tks Bosswhite.......... no sign any stain or marks on plasterboard in loft.
under roof also show no sign where rainwater could ingress.
have now painted with primer and when dry will emulsion and wait to see what happens.
The stain happens to be very close to where water tank sits but have...
sudden stain appear on bedroom ceiling approx 2' x 2" no sign of damp in loft. Have painted over 3 coats but has come through again......... any thoughts please.