Hello All. I'm dealing with a very neglected N. facing exterior wall with T1-11 siding that has got some kind of mildew or growth on much of it. It's red in some places and gray in others. Please see pictures. I've tried scrubbing and power washing a small area and while it's lighter, it's still present. It's even 'infected' some exterior plastic conduit! I'm sure we shouldn't just paint over it, and I'm hoping someone can suggest a remedy short of replacing the siding. Any help would be much appreciated. Cheers!
Hmm, that side does get sprayed by sprinklers and it's well water, but other exterior walls get similarly sprinkered on and don't have this. It's only the N. Facing wall. CORRECTION - my original post mistakenly said S. Facing.