Property: What gives with gravel?

That lovely new drive will soon drive you mad if you get the preparatio n wrong, writes Jeff Howell
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The Independent Online
GO ON, admit it. Your dream home has a crunchy gravel drive in front of it. A sweeping horseshoe of crunchiness. And in your dreams you cruise up in your Bentley/Ferrari/Roller (all right, not very pc, but we're talking fantasies here, OK?) making delicious crunchy noises, to be greeted by a gorgeous woman/man/dog while a servant appears with a bottle of champagne and two glasses on a tray. Welcome home, darling.

Well, dream on. Because when most people look at the fantasy image of a gravel drive, they see only the gravel and don't appreciate what's under the surface.

An amazing number of people order a lorry-load of gravel to be delivered, spread it around the front garden, and stand back to admire their handiwork. The only trouble is, when they try to walk over the newly laid gravel, they sink into it; then it really is like a dream - the kind of dream when you're trying to run away and you can't move your legs.

And if you try to drive a car over it, things can get even worse: the car sinks and the spinning wheels pepper the house with gravel, like shot from a gattling gun. Because what you see when you look at a properly laid gravel drive or path is only the top finish. The main part, like an iceberg, lies below the surface and represents considerable planning and preparation.

Robert Phillips, a groundwork contractor and gravel-drive specialist from Suffolk, has seen his share of disasters: "I've seen plenty of cars sunk up to their axles", he says. "People try to get things done on the cheap, and waste their money buying in a load of shingle - it just doesn't work." Mr Phillips thinks the problem is usually due to ignorance: "Drives are unforgiving. When you drive a vehicle over any surface, the forces involved are huge. If people knew a bit more about it, they'd realise that it's got to be costly."

That cost, for a "single" drive, will be at least pounds 40 per square metre. The sweeping horseshoe version will be more. So for a simple straight run up to the house, twice the length of your car, don't expect much change out of pounds 1,000.

But what should you look for in a quality gravel drive, and how do you know if your contractor's estimate includes all the required operations? Preparation is everything, and topsoil must be removed to a depth of at least 250mm. On a clay subsoil the area should then be lined with a geotextile - this stops the clay pushing up through the gravel but still allows water to drain downwards.

The "sub-base", 150 mm deep, must be a Type 1 material. The term comes from the old Ministry of Transport specifications for road building, and means a hard stone with the correct distribution of particle sizes - "well graded" in trade parlance. The best-quality Type 1 material is crushed pink West Country granite; recycled crushed concrete is a cheaper alternative, but check which one you are being charged for.

The sub-base must be well compacted with a heavy vibrating roller before 75 mm of Type 2 "hogging" is laid. This contains a proportion of clay, which will bind the stone together and will set rock-hard if allowed to drain through to the Type 1 below.

The hogging, in turn, must be well compacted before the next stage - spraying with two coats of bitumen. The best quality is hot-sprayed, which means it must first be heated in a tanker; the cheaper version is a cold- sprayed bitumen emulsion. In both cases the first coat has a single layer of gravel rolled into it, and the second coat is topped with the gravel surface. So your finished gravel drive is really only two stones deep - one stuck in, and the other "floating" on it.

All gravel drives will need edge restraint - either timber edging or brick or concrete kerbing - to stop the layers of stone escaping into the surrounding soil. And if your drive constitutes a new access, the local authority may insist you install a cut-off drain to stop water flowing down the drive on to the highway.

But once that's all done, your crunchy gravel drive will be there for ... well, not all that long, actually. The gravel is a "wearing" surface and after 10 to 15 years the top will need renewing. In the meantime it will have accumulated dirt, oil and fallen leaves, and quickly lost its smart good looks.

But let's face it, you don't install a gravel drive for the sake of appearances; you want it for its crunchiness - that delicious sound as you sweep off the road and pull up at the front door. What a great selling point - it's already a part of everyone's dream.

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