Tarmac Surfacing
This construction method can refer to either a footpath, a residential driveway or a car park.
There should be at least 4 layers to all Tarmac pavements:
Surface Course
The Surface Course is the final top surface. A surface course should consist of a small, hard aggregate, usually 6mm or 10mm, in a bitumen or asphalt binder. Coloured aggregates are sometimes used to mark out zones for the public.
Binder course
Binder Course Layers are generally the first levels of Tarmac to be layed. This is a load-bearing, strengthening layer of the pavement and should be at least 40mm-50mm thick. The binder course material should be laid and thoroughly rolled and compacted.
Sub-base Course
The sub-Base layer is usually a layer of hardcore or crushed rock which acts as a load bearing layer.
Sub-Grade Course
The Sub-Grade is usually compacted soil with all vegetation and loose top soil removed. The sub-base and base courses may be constructed from more than one individual layer of the specified material.
Sometimes an existing tarmac or concrete surface can be overlaid with a new surface course. This is acceptable provided that the new surfacing is properly bonded to the old surface.
