Blackening paving stones

Rekusu

What ho one and all.

I have three areas with paving stones; the patio, in front of the garage and the area in front of the front door.

The problem is that in two areas, the paving stones are becoming stained / blackening.  I regularly use the pressure washer but that does not restore them to  more or less, as bought shiney.

The garage and front door are both on the south side of the house and although the front entrance slabs are covered by the porch, the winter wind does blow rain onto them.  However, the entrance slabs are not discolouring but the garage and patio just look dirty and algae patchy.

I have slab cleaning solution in garden centres but they are expensive and I'm not sure if they do what they say on the box.

What can I do to clean them?   Detol?  Vinegar?

Thanks and toodle pip

Pete.8

Both Patio Magic and Wet & Forget have worked well for me over the last few years.
It needs to be used when the weather warms up a bit as it doesn't work when it's cold.
I was suspicious if it would work, but they were recommended by the firm that laid my drive and both work very well.
After spraying (I use a 5L pump spray) not much happens for about a week then the colour of the grime/lichen/algae changes and after a few decent rain showers it comes up pretty much like new.
It also stays that way for about 6 months.
So I use it around March and Sept.
My drive faces North so the top end gets sun but closer to the house gets none and over winter does get algae and marks from fallen leaves

PS - I also use it for the 20ft x 20ft of paving around and inside my greenhouse (which gets thick with green algae over winter) - it comes up a treat a while after spraying

bédé

Sorry, can't help.  I try to encourage my paving to look weathered and natural.  No shine or bright colours.  "Dirty and algae patchy",  perfect.

Plantminded

I agree with @Pete.8's advice, I use Patio Magic twice a year on my sandstone paving.  I was advised by the contractor who laid the paving not to use a pressure washer as although it removes the algae/staining it can also abrade the surface of the slabs making the surface more porous and more attractive for further algal growth.  Follow the instructions carefully and be patient.  You'll see an improvement within 2 - 3 days, often observed as round marks which outline the natural growth habit of algae - these disappear after the first rainfall.

LilyW

Is patio magic bad for the environment? Would hate to wash nasty chemicals into the surrounding soil

Rekusu

Everyone,

Thanks very much for the advice.  Was hoping there was something less expensive than PatioMagic, but seems that is the way to go.  Will buy some  and give it a go.

Pete.8

If you use a pump sprayer and not a watering can a little goes a long way.
5L will allow me to treat the drive and greenhouse area twice a year and usually still have some left over.

Rekusu

Thanks for the suggestion.  I do have a pump sprayer so guess that one can will do the job.

Given the in-climate recent weather, does one need to apply it when there is a dry outlook for a few days?

Desi_in_London

I'm not an expert, but both products @Pete.8 mentioned seem to have worked better for me when surface is dry, and it is not very hot and sunny but with temperatures at least 10 degrees or a bit above ( requires no rain for a few hours after application, but again a clear 48 hours or so dry spell post application has helped in my case ) 

Plantminded

That's exactly how I use it @Desi_in_London, although it does seem to work below 10 degrees, as long as it's not freezing.  Applying it late afternoon is also better so that it dries slowly.

Algon is an environmentally friendly alternative @LilyW.  Patio Magic is hazardous for aquatic life so apply only to the area that needs cleaning in the dilution recommended.  A pump spayer rather than a watering can gives more precise coverage without over applying.

Pete.8

I do my drive and greenhouse area in March and Sept.
The surface needs to be dry when you use it, so I choose a cloudy day when the temps are above 10c.
It's easier too when the surface is dry as you can see where you've already sprayed.
The surface only needs to be covered lightly, not soaked so it doesn't take long and it doesn't use a lot of product.