Black Mold on Limewash

[Roger H]

Hi all.

Solid stone, random rubble sandstone wall, external ground levels 2ft higher than internal. French drain and gravel buffer to exterior, separated from wall with plastic corrugated sheet to allow some external air to the wall. External and internal walls repointed in lime mortar, and internally lime washed (5% linseed oil, 1:1 water/limeputty mix). Black spots of mold coming through. Unheated room at present/some ventilation.

Any ideas? I'd guess, as the stone previously had water literally pouring through it last autumn, there may be a fair bit more drying out to do. But is there anything to dissuade the mold? Or should I wait, ventilate, heat and re-limewash? Any ideas much appreciated.

Thanks,

Roger.

 

[MdB]

5% linseed sounds a lot. Gervase suggests 0.5%. The extra linseed might be what the mould is feeding on.

 

[Pford75]

Agree with your diagnosis that this is most likely residual dampness in the wall which will take some time to dry.

There has been some debate on the forum about the effectiveness of dehumidifiers (some believe this will draw more damp into the building). I'm of the view personally that they help rather than hinder and may speed the drying process.

As for the mould, I would try a mild bleach solution or jeyes fluid.

 

[Roger H]

Thanks for that. Actually, it's more of a glug in the bucket than 5% but maybe i'm overdoing it. I'll ease up on the linseed, spray some bleach on and await the drying out power of this glorious summer to work its magic...

 

[Schoolmarm]

There has been some debate on the forum about the effectiveness of dehumidifiers (some believe this will draw more damp into the building).
.

Actually some people say only when there is a constant source of damp outside the building ie. t'other side of an underground cellar wall.