No matter how much care is taken, weeds may occasionally appear on the surface usually as a result of wind blown seeds. Small weeds can be removed by hand without damaging the surface. In damp and shaded areas the surfacing may attract moss.
A pathway moss killer can be used, but do not use a moss killer which contains iron sulphate, it will stain the surface. Localised areas of self-set weeds can be treated with domestic weed-killers without causing damage to the surface. Oil-based weed killers should not be used.
Care must be taken in its application because of a possible hazard to children. After removal of weeds wash the whole area with water to remove any residual chemicals.