The loft in my semi (1930's) the beams and roof joists have white moss type stuff,more like spots of white,i wiped it a few weeks back but is now come back...what is it and what causes it? 2 beams have wet rot but only about 2-3 inch's long and 4 inch wide (not much i know) is it something to worry about ? ive treated the beams with cuprinol 5 star treatment,just concerned with the white spots.
loft has new insulation and is boarded up for storage use.
Roof is tiles that were cemented on in them old days so theres no felt.