Patio black spot treatments

Ant555

orangecrush said:

This is one of the products that I was thinking of buying, but it is essentially just bleach. It says it is harmful to plants and will kill grass - ok, that’s fine. But what confuses me is there’s another (more expensive) product that is also bleach based that says it won’t kill grass or plants. 

If they’re both bleach I can’t see why one would be safe and another not?! In which case I might just go for this cheaper one 😁

thanks for your input! 

Your pics look very similar to the state of my own patio before.

I did actually use some left over product on a small paved area at the bottom of the garden last year that has no drains nearby and used lots and lots of water rom my hose to flush it away when I was done  - essentially everything washes towards my lawn as there is nowhere else for water to go and the grass was fine last year and is still fine.

I cant remember the instructions but it does fizz a bit and I have a hard yard brush that I scrubbed the patio with before leaving it for a few hours then washing off with lots of water.

pmartin86

I can see why you'd want to clean those up, but I could also see you enjoying them as "well worn", sometimes a garden doesn't have to be perfect!

That being said, I'd guess based on those pictures that its been heavily neglected  for years and you've the lichen and algae have slightly penetrated the surface which is why their showing even though you've pressure washed. I don't see any harm in you trying one of the "beach based" products mentioned, I'd recommend getting a sprayer though if you don't already have one, and give it a goad soaking, you want it to penetrate as deeply as possible, id also do it on a cooler, overcast day to help prevent evaporation (not rainy though) give that a coat or 2 and see what happens. 

If you still don't get any joy and are still unhappy, you could look at some of the "acid wash" type products, but be aware these can cause more damage than good and if you're not sure or confident with chemicals, probably best left to someone who is - That being said I once cleaned a small (ancient) path at my mums house with some Sodium Hypochlorite and it come up great - This was (quite) a few years ago mind so might want to check the relevant "laws" now if you go down this route.

This gives you an idea of how it works though:

How to clean a concrete drive with no power washer - soft-washing - Sodium Hypochlorite - Hypo - YouTube

shiraz99

The black spots are most certainly cause by lichen. Bleach is pretty much the way to go. Don't buy the expensive, "specialist" products as they just contain bleach by another name, ie, sodium hypochlorite. Just buy the big bottles of the stuff from the likes of Lidl, Aldi or Home Bargains etc and use that.