On 21 Apr, 00:05, wrote:
Any advice for fungus growing on inner walls of a 1930's house? It is
at top of walls so I think not rising damp.

If I just re-paint will it re-occur? Is there any treatment I can give
before repainting to prevent recurrence?

When I moved in the house had to be re-wired and the electrician
fitted a ventilator from the upstairs WC to an outside wall, could the
cold air coming in through this be causing the damp/fungus and would
blocking it up be any use?

Do I need to keep the rooms affected heated? Better ventilated?...

Dear grouchy.old

Some id would be the first step
IS is a fungus? or efflorescence or mould?

What colour?
Is there a sporophore or are you looking at mycelium?

Perhaps a photo?

It could be Aspergillus niger (if a mould from condenstion)
plaster fungus
dry rot sporophore (hope for your sake not)

What is the substrate?

Is there an obvious water source outside?

When you have answered these questions I would be of more use to you
Chris