Drip Grooves in Paved Treads
Whenever a paving slab is designed to extend beyond a terraced wall or step riser, acting either as an edge to the patio or tread on a set of steps, it is advisable to ensure that a ‘drip groove’ is sawn into the underside of the slab. This groove should run the full length of the overhanging slab, with each groove marrying up with its neighbour to provide a continuous line. A groove of 5mm wide x 10mm deep will suffice, similar to the groove found under a window sill.
The purpose is to prevent rainwater from running down the face of the wall/riser causing discolouration of the brickwork/rendering. The slab should have a fall towards the front edge of 1:60 to prevent water from sitting on the slab and causing issues with ice and algae from creating a slip hazard.
