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I am thinking of replacing my asphalt driveway with granite paving. The problem is that if I build a mortar bed for the granite blocks it will be level, so that water will sit on top of the driveway and not drain off.

In professional road building the road surface is crowned to provide for water shedding.

How can build the driveway so that water sheds off?

  • A mortar bed completely defeats the environmental and practical benefits of a permeable surface like granite blocks. Use something else that drains naturally. – isherwood Nov 10 '16 at 17:50
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You don't need to crown the driveway, just make sure that the runoff slopes away from the house at to one and a half inches per ten feet; so if your driveway is 20ft long, the bottom should be 3inches lower than the top. If possible, pitch in two directions, so water runs to the bottom and to the side. (the recommended minimum is 1" to 10', but I like to play safe)

You don't set granite blocks in a mortar bed - it's too rigid and brittle. Use blocks designed for a vehicle driveway (they're thicker than the normal pavers you can buy). Put a good base below that - 8 to 12 inches, compacted. Anything less will not take the weight of the cars for too long. Spend a lot of money and time getting the base right, and the block part of it will be fun.

The internet has a lot of help on how to build and install driveways. My advice is only as follows;

  1. Prepare your base such that it extends sideways 50% of the depth. So if you're working on a 12" base, you want to prepare an area 6" extra all round (so a 10'x20' drive needs an 11' x 21' base)
  2. Rent, or buy, a vibrating plate compactor. It's worth it for the speed and quality of finish.
  3. Don't think that you can get away with a thinner base because you have hard ground. You may get away with it, but it's better to be absolutely sure that the base you've built is to your specifications, not Mother Natures.
  • How do I slope the base? If I add stones to a sloped surface, won't they crack due to unequal pressures? – Tyler Durden Oct 8 '16 at 18:11
  • Building a driveway is a massive subject - lots of videos on the internet. Basically, you dig out to the depth that you need, put woods forms around the area you need to build (use the forms to set the slope), and set their top edge to your final height. Add roadbase in 2" lifts. Compact each. The last layer is sand, which is also compacted, and leveled to the top of the forms. Then place the blocks on top of the sand (make sure they're constrained at the edges. Fill the gaps with polymeric sand, and you're done. – PeteCon Oct 8 '16 at 21:12
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    Other than poly sand I agree, poly sand is much more expensive and I find it to only last 1-2 years longer without needing additional sand added at 2-3x the cost. – Ed Beal Oct 9 '16 at 21:28

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