In Telegraph of 23.8.14, the Ask A Builder column dealt with the following question from MW of Basingstoke …
“I want to install a gravel path around my house. Owing to the confines of the area, and the fact that it may be too expensive to pave, the gravel will be right up against the house. I’m making sure not to raise the level of the path above the damp-proof course (DPC), but how much lower should it be?”
Telegraph consultant Jeff Howell said:
“Ground levels adjacent to any building must finish at least 150mm (6in, or two brick courses) below the DPC. This is to prevent rain splashing off the ground and wetting the wall above DPC level, where it might track across and cause damp patches on the inside.
“Installing a gravel path or drive is not quite as simple as it might sound. If you just spread a load of gravel on to the ground, it might look pretty for a few months, but will soon sink into the earth, and become colonised with weeds.
“A properly constructed gravel drive or path is like an iceberg, in that 90 per cent of it is out of sight. You need to excavate and remove the topsoil, line the subsoil with a geotextile, then lay and compact hardcore. Follow this with a layer of compacted “hoggin” – compacted clay, gravel and sand. This is then sprayed with hot bitumen, and has a layer of pea shingle rolled into it. The final “wearing surface” of pea shingle is spread on top of this. So your finished gravel path is actually only two stones deep – one stuck into the bitumen, the other floating on top of it.
“Don’t forget that a gravel path also needs edge restraint – timber, brick or concrete kerbing, to stop the layers of stone and shingle escaping into the surrounding soil.
“I think you’ll find paving a lot easier and cheaper. You will still need to remove the topsoil, but you can then just line with a geotextile and bed the paving slabs on sharp sand.”
For more Jeff Howell, see http://www.askjeff.co.uk/