Paving the Way with Pride and Passion
Tarmacadam: Layers of Construction
As with most other driveway surfaces there are a number of layers involved, starting with the foundations. Typically excavations will go down to 16 to 18cm for a driveway or path, then a sub-base of crushed hardcore will go down and be rolled with a road roller. Edging kerbstones, or a decorative stone or concrete block, whatever you have chosen, should then be laid and haunched on both sides so that they will be supported while the tarmac is laid.
The tarmac will go down in two layers, first the base and then the top surface known as the 'wearing' course. The base layer will use a larger grade of aggregate and has to be delivered in a heated lorry. Once laid roughly along the site of the driveway the tarmac is spread out and levelled with large, sturdy rakes. The roller then comes over again to compact the base layer, only stopping when it no longer makes marks on the surface.
Top Surface and Finishing
The wearing course has smaller grains of aggregate so there's a finer, better looking and harder wearing top layer. In the future, if the job has been done right all the way through, the driveway can be rejuvenated by skimming the wearing course and re-laying it, a process known as 'overlay'. The laying is done in much the same way as the base course but with more care, and a professional crew will be looking for a tolerance of around half a centimetre across the levels.
The drive will set fairly rapidly and within an hour or so it will be available for careful use. It's best to avoid aggressive accelerating or braking for the first week or so, and in particular turning the wheels when the car is at a stand-still, something that's all too easy with a power-steered car.
Tarmacadam & Setts
