The UK has a damp climate. This can cause real problems for natural stone patios, especially some of the softer varieties of sandstone paving. Natural stone is porous and the surface of a patio can be the perfect breeding ground for alga and fungus growth. Slate and limestone paving are not as porous as sandstone so they will not be as badly effected by algae, but they can both still be susceptible to algae in damp, north facing gardens. When we sell stone to a customer we are always sure to find out what the conditions in the garden are so that we can recommend the right type of stone.
We often get call from people asking how to prevent there patio from algae. Sealing natural stone will reduce the effects of algae but not get rid of the problem altogether. London Stone think they have found a product which will get rid of algae, once we have tested the product we will reveal all.