My son has a late Victorian/early edwardian terraced house built of brick and tile. It still has its original fireplaces which he wants to keep although two are blocked off. In one of the rooms, with a blocked off chimney he gets condensation coming through on the chimney breast, showing as darker coloured patches. The loft does suffer from a degree of condensation, and I wonder if this is the reason. How could this be rectified. He had a specialist in with regard to a smll damp problem elsewhere who said that this was nothing to worry about, although he would like to address the problem, especially since his survey, on purchase recommended this. Any tips or suggestions would be most welcome.

If the trouble is just on the chimney breast, then the problem is probably due to the ingress of rainwater into the chimney itself. As the fireplaces have been blocked off, it would appear that there is little or no air getting up the chimney to dry off the rain getting in. I would suggest that a weather-cap be put on the chimney pot. I wouldn't leave it as it is bcause eventually you could get structural damage.

I think the chimney cap is a GREAT idea.... Also you might want to find out if the fireplace was just covered or if it was filled in as well.

All areas that are not heated will have condensation. Ventilate the area if you can.

Depending on where you live and what the weather conditions are when the water is appearing, you probably have a problem of condensation caused by the warm humid air coming into the uninsulated chimney and condensating as it contacts the air conditioned air of the house.
If this happens in the winter it is for the opposite reasons.

In general, dead unconditioned spaces should be well ventilated and separated from conditioned spaces with a vapor barrier. It really depends on the climate of the site, so if you could give the location it would be helpful.