Hi folks, first timer but reading posts for ages, great site and hope to be helpful to others to.
I have an existing old stone shed which i'm currently converting into a bedroom. However, the external rendering, which is painted white, has patches of a reddish sort of mould on it and i'd love to know whats causing it and how to get rid, any ideas? Apart from being un-sightly i'm drylining the internal walls and hope i'm not going to make it any worse, may have to put in air vents to the 'cavity'.
I'm thinking its a typical sand/cement render which is'nt allowing the moisture in the stone walls to evaporate, causing the red mould! I'm sure the walls don't have any dpc and i expect if i paint it, the red mould will just come back. Thanks alot for any replies.