Blackening paving stones
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