The wall in question is the outer wall of a second floor flat that I let. Unlike most scenarios described in these forums, The mould is very fine and grey, rather than black. More liike a 'paint effect'; it brushes off, and I have washed over it with a fungicide.
It is most noticeable under two windows, at its worst in a dark secluded corner of the same wall. The wall does not feel particularly damp, and the mould is not charecteristic of the black, blistering fungus that one sees when water is leaking in from outside. The pointing seems reasonably good , and the gutters above were replaced recently. The plaster/ paintwork is perfectly sound and not cracking away at all. There is no musty smell, or any charecteristics of dry rot. The flat below has no similar problem.
I suggested to the lodger that the cause was excess condensation, and might be cured by more ventilation. The windows are D/G units , and condensation does manifest itself on the kitchen window. The heating is by storage heaters, on a low setting.
I added that the flat, being on the second floor of an older property, has no 'outside door' to speak of, and no draughts or throughput of air, so one has to make an effort to change the air in the flat.
Am I right in thinking this?
Storage heaters are particularly poor a poor means of heating a property as most residents cannot use them properly and dont always give you the heat when you need it.
Obviously you do need to vent the flat especially with double glazing as the condensation does need to go somewhere, have the windows got trickle vents? if not ensure they are open a small amount.
Are the trouble windows in a bay? if they are you may find the brickwork underneath is not as thick as elsewhere and therefore causing a cold spot, if this is the case then you may need to consider insulating this area, plasterboard the over insulating material then a plaster skim should solve it.
But make sure your tenant heats and vents their property adequately whilst prevent unnecessary condensation.
DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!