What do you use to get moss/algae off paving slabs?

[Fluffycloudland77]

The front of our house gets little sun & the stone window sills are going green!.

Get a pressure washer! I spent years trying various treatments for green flagstones in a shady garden with intensive yard brushing and rinsing which help a tiny bit. Borrowed a pressure washer before I put that flat up for sale and it was amazing. (Be prepared to get absolutely filthy yourself though) Couldn't believe I'd been wasting my time for so long....

Yes, pressure washers are great for that. But mine won't reach to the end og the garden so I find Jeyes fluid solution does a good job - tho' it's not very environmentally friendly.

Don't bother with products, a Power Washer will do the job. Be prepared to get wet & wellies are a must. Set aside plenty of time,it's addictive cleaning. Don't buy cheap or you'll replace it in a couple of years. A Karcher is superb. Happy blasting.