Tarmac — more accurately, open-graded or dense-graded macadam — has been the default British driveway surface for decades. It is cost-effective, quick to install (a typical domestic driveway is done in a day), and when laid properly it is extremely durable. The issue is that tarmac is also the material most associated with rogue traders — the combination of fast turnaround and a finished surface that looks adequate even when the base work has been poorly done creates obvious temptations for less scrupulous operators.
What a Correct Tarmac Installation Looks Like
A properly installed tarmac driveway involves: stripping the existing surface and vegetation; excavating to the appropriate depth (at minimum 100mm for cars, deeper on soft ground); laying and plate-compacting a sub-base of MOT Type 1 crushed stone; applying a tack coat to the prepared surface; and laying macadam in at least two layers — a binder course and a wearing course — with each layer compacted by roller. The total finished depth should be at least 50–75mm of macadam over the sub-base. A single thin layer of tarmac laid directly over compacted soil or an old concrete base is not a proper installation and will crack and settle within a few years.
"There is no such thing as a proper tarmac driveway that can be installed in a morning by two men with a small roller. A legitimate job requires machine-mixed hot macadam, a plate compactor or roller, and adequate time for each layer to be properly compacted before the next is applied. Rush and shortcuts at this stage create a surface that looks fine on the day but fails within two to three winters."— Asphalt Industry Alliance — Homeowner Guidance
The Cold-Mix Problem
Hot-mix macadam — heated in a plant and delivered ready to lay — is the correct material for a durable driveway. Cold-mix tarmac, available in bags from builders merchants, is a repair material for filling potholes and small areas. An unsolicited caller offering to tarmac your driveway from "leftover material from a job nearby" is almost certainly using cold-mix, which does not compact or bond properly and will degrade quickly. Walk away from any such approach.
Edging Restraints
Tarmac has no inherent structural edge — without a physical restraint, the edges will spread and break over time, particularly where vehicles mount kerbs or cross the edge repeatedly. A properly installed tarmac driveway should have a concrete haunching or block paving edge course to contain the macadam. Ask specifically about edge details when comparing quotes.
"Edge restraints are essential for a tarmac driveway. Without them, the macadam will spread laterally under vehicle loading and the edges will crumble. The cost of fitting concrete haunching or a block edging course is small relative to the overall job cost, but it makes a significant difference to the longevity of the surface."— Which? — Tarmac Driveways
Planning and SUDS Requirements
Standard tarmac is impermeable. Laying more than 5m² of impermeable surface in a front garden in England requires Householder Planning Permission, or the run-off must be directed to a permeable area (lawn, border) rather than the road. Porous tarmac (open-graded macadam) is available and SuDS-compliant, but requires a different sub-base specification and costs more to install. Confirm with your contractor which specification applies to your situation before work begins.
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