Mould identification/treatment

It looks as though it's in a roof, but I'm not certain from the pics. If this is wrong then disregard the rest of this message.

This fluffy stuff is fairly common in roofs. It is NOT a fungus. From the photographs it is difficult to tell which, but it is either crystallisation of salts, possibly from chemicals in old preservation treatments (favourite), or else surface mould of some kind, although this is normally black in colour. Both situations are due to surface dampness on the timbers, most likely condensation. The "fluff" indicates the dampness has dried and it can just be brushed off and forgotten.

We've been through the causes and cures for roof condensation several times recently so there's bound to be either a current or archived thread you can look at. Warm houses and cold roofs this time of year encourage condensation and it's not really a major problem unless the timbers remain wet for weeks, when wet rot might become a problem. Dry rot almost never occurs in roofs.

Things to do: Look for any roof leaks after a rainy day and make sure they are cured Increase ventilation if possible, both in the roof and in the rooms below Try to keep vapour production to a minimum.

Peter