Indian Sandstone Patio - Restore Colour

JMR

Not sure if this post belongs here or in the DIY forum, so mods please move it required.

Patio is in place approx 12 years and is looking very tired, most of the original colour is now faded to a dull grey with a lot of black algae spots.
Any previous attempts to clean it have only resulted in removing the grime and brightening the stones but not shifting the algae and certainly not restoring the colour.

From a small bit of research, it looks like I need a very powerful washer?
I was looking at this Karcher K7

https://www.kaercher.com/ie/home-garden/pressure-washers/k-7-premium-full-control-plus-home-13171360.html

It's quite expensive so was wondering what people's thoughts are?

HeidiHeidi

I'm jumping in here because I'm in exactly the same position - I've kept the stones reasonably clean by applying Algon a few times a year, but while it's very effective it just seems to bleach them. If you just want to clean the stones and get rid of the black spots, I can really recommend that stuff, I got it in a garden centre and just apply it with a sprayer.



I'd dearly love to restore the colours though, if that's even possible?

diggerdigger

JMR wrote: »

Not sure if this post belongs here or in the DIY forum, so mods please move it required.

Patio is in place approx 12 years and is looking very tired, most of the original colour is now faded to a dull grey with a lot of black algae spots.
Any previous attempts to clean it have only resulted in removing the grime and brightening the stones but not shifting the algae and certainly not restoring the colour.

From a small bit of research, it looks like I need a very powerful washer?
I was looking at this Karcher K7

https://www.kaercher.com/ie/home-garden/pressure-washers/k-7-premium-full-control-plus-home-13171360.html

It's quite expensive so was wondering what people's thoughts are?

I had a sandstone patio with awful black spots. Couldn't get them off for love nor money. Used every chemical under the sun, and very powerful petrol washers.

What worked in the end was very thick black plastic. Put it down to block light. 2 months later, the spots were gone. They come back though. I was told by a gardener that there was a glut of cheap sandstone here at the end of the Celtic tiger. It's not suitable for Irish damp weather, so the algae takes hold. Don't know if true.

Hocus Focus

That Algon promotes itself as an organic product. I find that such products may be less than successful as opposed to the usual chemicals. I would recommend a product containing Benzalcoium Chloride, such as Patio Magic. Here is a link to a discussion on it, mentioning black algae spots on another forum to which I subscribe:
https://forums.ybw.com/index.php?threads/patio-magic-et-al.471521/