A tarmac drive isn’t the cheapest form of driveway but it must have a proper edging to protect that investment. Without it, the edges of the driveway will crumble away. Water will get in under the fabric of the top dressing and eat away at the foundation layers.
Arrangements With a Contractor
Tarmac does become cheaper per square yard for a longer drive. Its chief disadvantage, in terms of the domestic driveway market, is that it isn’t easy to do as a DIY job; it’s much easier for a contractor who has all the specialist tools (see our article The Art Of Laying Tarmac on this site).
If you get an amenable contractor, you can ask if they are prepared to allow you to do the edging and then come along and lay the tarmac later. It’s a tricky proposition for the contractor because if there’s a failure of the driveway, the contractor could get caught in the middle of a blame game. As long as you can come up with an agreement that puts the contractor’s mind at rest, you can then proceed.
It’s become common to see timber edgings for tarmac paths and driveways, but it doesn’t last particularly well and if it warps, gaps can open up between the edging and the tarmac.
Those gaps may close after a warm summer if the tarmac oozes into them, but you are then thinning the tarmac layer at the edges. If the course of your driveways means that people often drive over the edge, this could all lead to premature breakdown of the drive.
If you do want to put timber edging down, perhaps everyone else in the street has it, or you are selling the property shortly, make sure it is laid down flush. Any timber that’s proud of the driveway will be ragged and splintered within days. Take a look at our article on Timber Edging in this section for more details.
Concrete Edging for a Tarmac Drive
Mounting block or bricks on a bed of concrete is much more reliable and longer lasting. You can use kerb blocks made for the purpose but they can look a little municipal. For a domestic drive, it might be better to pick up something a little more decorative.
Once you’ve Excavated The Area, mark out the edges at the sides of the drive using pegs and string or a biodegradable spray paint. Then make up the concrete, making the mix stiffer, so that it stays in place. Lay the concrete down in a ridge about 6 to 8in wide, high enough to support 10-15% of the block’s depth when pressed into it.
Then you need to build up a layer of concrete on the inside of the line of edging blocks to support them. This is called ‘haunching’ and will help prevent the spreading strain put on the edging when a car uses the drive.
Haunching should stop about an inch from the top of the edging block and taper away from it. Make the haunching layer about as wide as the edging block. But if this would make it unnecessarily wide, build wooden formwork inside the run of edging and lay concrete between that and the edging block.
Laying the Driveway
It goes without saying that you should pay strict attention to levels throughout this as you want the driveway to look as good as possible when it’s done. Then protect the edging with a thick, heat-resistant plastic layer and call in the tarmac.
If you are using a contractor to lay the tarmac, get him to check over your work at different stages to avoid any expensive mistakes. After all, it’s not going to save much money if you are going to have to do all the work twice.