Slippery Paving Stones.

Both natural and concrete paving stones can become slippery if they are in the shade or under trees that loss there leaves in the winter.This is firstly because the sap from the tree leaves combined with the shady conditions makes it an ideal place for mosses and lichens to grow.You will find that especially the lichens are very small plants and are hard to see unless you look very closely.
When the paving becomes wet or damp through rain or a heavy dew its these lichens and mosses that become very slippery causing the problem.
The solution is to make a point of sweeping up the leaves in the autumn as they fall and also to treat the paving with Jeyes fluid and/or a dressing of iron sulphate which will kill the mosses and lichens.