The solid black surface of tarmac is a familiar sight on roads across the UK, and it might just be a perfect choice for your driveway too.
A versatile and reliable option for road surfaces, it has been used in public infrastructure for over a century. If you are considering installing a new driveway, tarmac is an affordable and straightforward choice.
What is a tarmac driveway made of?
Tarmac, the generic name for road surfacing, is not entirely accurate, as modern tarmac does not actually contain traditional tar.
The binding material for the aggregate used in today’s roads is a form of bitumen, a petroleum-based product rather than the natural tree resin or coal tar. The semi-solid bitumen is heated and used to hold together a base of crushed stone or aggregate.
It is then flattened into position to remove any air from between the gravel pieces, which makes it less prone to unevenness or sinking. The process also ensures that water cannot enter gaps, so the cracks that develop in other driveways because of freezing and thawing are rare.
As it cools and dries, the tarmac hardens into a smooth yet textured road surface. The finished structure can expand and contract with changes in temperature without cracking, which makes it perfect for London’s fickle climate.
How thick should a tarmac driveway be?
The ability of tarmac to withstand heavy loads is well known; there is a reason why British roads and motorways are surfaced with it. However, a tarmac surface that is too thin will wear down too quickly, and you will end up with potholes that need repairing.
More important is the sub-base on which the tarmac is laid. For your driveway, it should be more than 150mm of compacted crushed stone. However, if you have a van, lorry or RV parked there regularly, the sub-base will need to be much deeper.
The same logic applies to the tarmac layers applied on top. The heavier the vehicles and the more the traffic, the thicker the layers of blacktop.
UK standards for constructing public roads require more than 75mm of tarmac for residential access, while motorways are required to have over 400mm to account for incredibly heavy loads and traffic.
If the tarmac is not thick enough, it will not last and will fall apart due to cracking. The thickness is vital for evenly distributing the weight of vehicles and for longevity.
The finished thickness for a driveway surface, not including the sub-base foundation, should be in line with the standards for domestic access roads – 75mm and above.
What are the advantages of a tarmac driveway?
- Quick to install; it only takes one or two days, depending on the length and width of the driveway
- Cheaper option than block paving or resin
- It can be used to cover any shape or area size without seams, so reducing trip hazards
- Highly durable and requires little to no maintenance
- Withstands greater loads than block paving without damage, perfect for vans and RVs
- If they do develop cracks and holes, tarmac surfaces are easy and cheap to repair
- Better for your budget as it is cheaper per square metre than block paving
While a tarmac driveway may not have the desirability and pretty patterns of block paving, it is a solid and functional alternative that is easy on your budget.