Concrete wearing surfaces
These are covered by BS 8204, Screeds, bases and in-situ floorings, Part 2: Concrete wearing surfaces– code of Practice (2004).
A wearing screed is a screed that serves as a flooring and was formerly known as high strength concrete topping or granolithic topping. It typically contains a hard rock aggregate up to 14mm to enhance the wearing resistance. It can be laid in two forms, either monolithically, as an integral topping laid before the base has initially set, or as a separate screed.
When laid monolithically thickness is in the order of 15 ± 5mm whilst the optimum recommended thickness for separate bonded wearing screeds is between 25mm and 40mm.
BS 8204 contains classifications for surface regularity and abrasion resistance.
When a concrete wearing surface is required over a DPM an overslab of at least 100mm, (increasing to 150mm to minimise curling) should be used.
Further reading: PYE, PW and HARRISON, HW. Floors and Flooring, BRE, 2003.