Exterior stone walls turning green at base

[DampedOut]

Well, this is exciting.

Over the summer we had a thick cement facade removed and the original, southwest-facing stone facade repointed in lime. The work was finished in October. Nothing on the inside walls was touched. The autumn storms brought a lot of driving rain, so much so that it dripped out of the plaster above a window and formed a little puddle on a stone windowsill.

That's over now. And the humidity meters inside say humidity is dropping. All great.

And yet.

The facade wall is turning green from the ground up!

What could be behind this? Is it ground levels? They're about the same as inside the house. Is it just water vapour leaving the building and creating a hospitable environment for mosses? I'm not really against the look tbh and I'm not sure it's escapable in Cumbria anyway. I just want to make sure this is not bad news.

 

[Cubist]

Would these be north sides or well shaded areas of the walls by any chance?

 

[DampedOut]

Surprisingly, this faces south/southwest. And no shading, it overlooks space for 3 cars and another house's driveway. And the street beyond that too.

 

[Cubist]

A lot of the pointing looks fairly new, was it recently done?

You may want to consider a lime wash when the weather improves. I found that, provided a cleaned the lichen (whatever it is) off and gave our walls a good coat it seems to inhibit/prevent the return of the stuff.

 

[DampedOut]

Yes, the whole thing was repointed over the summer after the cement facade was removed. Such a relief too! It was a great result with a project where you have no idea what you’ll find behind the façade.

So it’s just a worry this is a sign of something bad happening but it may not be at all. I’ve just never heard of it.

 

[malcolm]

Wet walls will tend to attract condensation and green stuff on the outside. It's possible the wall hasn't had a chance to dry out yet.

 

[a twig]

Ditto what Malcolm said, wall will almost definitely still be drying out

 

[philpjuk100]

I know that chemicals are not normally approved but the render on the front of my house had light mold growth on it and I tried a product called "wet and forget" I found it on the internet, and when diluted and sprayed on with a plant sprayer it made no immediate difference but after about a month my wife noticed all the mold had gone. Now a couple of years later I think it may need a second application..

 

[philpjuk100]

• Non-caustic, Non-acidic, Contains no bleach, No shelf life and is Biodegradable, PH8 (Pure water is PH7).
• One 5L bottle makes 30L of product. Covers 100-300m2 depending on porosity of surface.
• Mix 1 part Wet & Forget with 5 parts water in a garden sprayer then 'Wet & Forget.
• It's easy, no scrubbing, rinsing or water blasting required.
• Just Wet the Area & Forget it. It worked for me but I don't like using chemicals!

 

[Lacan07]

Well, this is exciting.

Over the summer we had a thick cement facade removed and the original, southwest-facing stone facade repointed in lime. The work was finished in October. Nothing on the inside walls was touched. The autumn storms brought a lot of driving rain, so much so that it dripped out of the plaster above a window and formed a little puddle on a stone windowsill.

That's over now. And the humidity meters inside say humidity is dropping. All great.

And yet.

The facade wall is turning green from the ground up!

What could be behind this? Is it ground levels? They're about the same as inside the house. Is it just water vapour leaving the building and creating a hospitable environment for mosses? I'm not really against the look tbh and I'm not sure it's escapable in Cumbria anyway. I just want to make sure this is not bad news.

View attachment 9819

View attachment 9820

View attachment 9821

View attachment 9822

View attachment 9823

View attachment 9824

If its getting hit by the sun I'd say it was just standard bio growth, the sun is interacting with the moisture escaping the wall.

 

[Drayton]

The inner wall will be drying still, certainly, but the bottom of the wall will be damp frequently in the winter? (Oct 2022 Cumbria rainfall c166mm, Bedford c91mm, November's data not out yet.)

ETA Sun??

 

[DampedOut]

I know that chemicals are not normally approved but the render on the front of my house had light mold growth on it and I tried a product called "wet and forget" I found it on the internet, and when diluted and sprayed on with a plant sprayer it made no immediate difference but after about a month my wife noticed all the mold had gone. Now a couple of years later I think it may need a second application..

Thanks for this tip. I think, provided it's not doing any harm—and isn't a sign of something going wrong—we're prepared to let it go. But it's good to know that if it starts to sprout ferns and trees there's something we can do about it.

It's amazing to see this much greenery within 4 weeks of the cement façade removal and lime repointing finishing up. "Life finds a way."