Tarmac (short for tarmacadam) is a road and driveway surfacing material made from crushed stone or gravel aggregate bound with bitumen - a black, viscous petroleum derivative. It is laid hot (typically at 150-180 degrees C) by machine or hand, then compacted with a roller while still warm to produce a dense, waterproof, skid-resistant surface. The term 'tarmac' is often used colloquially for any black road or driveway surface, though the correct technical terms are bituminous macadam (bitmac), dense bitumen macadam (DBM), or hot-rolled asphalt (HRA) depending on the specification.

What is the difference between tarmac and asphalt?

In everyday use, tarmac and asphalt are used interchangeably to describe bitumen-bound surfacing. Strictly, tarmacadam uses tar (a coal-tar derivative) as the binder, while asphalt uses bitumen (a petroleum derivative) - modern road and driveway surfaces are almost exclusively bitumen-based, so 'asphalt' is technically more accurate for modern surfaces. Hot-rolled asphalt (HRA) is used for heavily trafficked roads; dense bitumen macadam (DBM) is a looser aggregate mix used for base and binder courses. For domestic driveways, 'bitmac' or 'dense macadam' is the normal product.

How thick should a tarmac driveway be?

A residential driveway is typically constructed with: 100-150mm compacted Type 1 MOT sub-base; 50-60mm binder course (base layer of larger aggregate bitmac); and 25-30mm wearing course (fine surface course). Total asphalt depth of 75-90mm over 100-150mm sub-base provides a durable surface for cars and light vans. For HGV access or heavily loaded areas, the total construction depth increases significantly. The sub-base depth depends on the bearing capacity of the soil below - softer clay soils require deeper sub-base.

Does a tarmac driveway need planning permission?

Standard tarmac is impermeable - rainwater runs off rather than draining through it. Under rules introduced in 2008, new or replacement impermeable surfaces in front gardens over 5m2 require planning permission in England. To avoid planning permission, the surface must be permeable (porous asphalt is available) or drainage must be directed to a lawn or border rather than to a road or drain. In conservation areas, additional planning restrictions may apply. Rear garden and side path surfaces are generally not affected.

External Works noun

Tarmac

/ ˈtɑːmak /

Also known as: tarmacadam, asphalt, bitmac, bituminous macadam, blacktop, macadam

Definition

Tarmac (tarmacadam) is a surfacing material made from crushed aggregate bound with bitumen, laid hot and compacted to form a dense, durable, and weatherproof surface. It is used for roads, driveways, car parks, paths, and playgrounds. A standard installation comprises a compacted granular sub-base, a thicker binder course of coarser aggregate bitmac, and a finer wearing course as the finished surface. Modern versions are strictly bituminous macadam (bitmac) rather than true tar-bound tarmac.

In practice

Tarmac must be laid within a few hours of leaving the plant, as it cools and hardens once removed from heat. Machine laying with a paving machine gives the most consistent finish; hand laying is used in confined areas. The surface is compacted with a vibrating roller - typically two passes in vibratory mode and one or two static passes to finish. Edge restraints (concrete haunching, granite kerb, or plastic edging) are essential to prevent the edges spreading or crumbling over time.

A key advantage of tarmac over block paving is speed - a standard domestic driveway can be completed in one day and driven on within a few hours. Disadvantages include susceptibility to oil and petrol spillage (which dissolves bitumen), softening in extreme heat, and the difficulty of accessing services beneath it without significant disruption. Tarmac driveways typically need resurfacing or resealing every 10-15 years. Spray and chip (surface dressing) prolongs surface life without full reconstruction.

Building Regulations

Planning (front garden)Impermeable tarmac over 5m2 requires planning permission

Porous alternativePorous asphalt (permeable) does not require planning permission

Road standardBS EN 13108 - Bituminous mixtures

Under the Town and Country Planning (General Permitted Development) Order 2008, laying an impermeable surface (including standard tarmac) in a front garden over 5m2 in England requires householder planning permission. Porous asphalt (which allows water to pass through to a granular drainage layer below) qualifies as a permeable surface and does not require planning permission. In Scotland, Wales, and Northern Ireland, different planning rules apply.

Full Building Regulations guidance

Tarmac

Just so you know...