The driveway's asphalt edges are crumbling. Rainwater is washing away mulch. Plus, cars are straying onto the grass, leaving tire tracks where they don't belong. One solution to all three problems? A crisp boundary made of Belgian block.
The rough-cut rectangles of stone, first carried to these shores as ballast in the bellies of ships, have been used for paving since colonial times. When placed side-to-side along the perimeter of the driveway, they add a touch of distinction as they protect vulnerable edges from eroding or being split apart by shoots of grass. And there are the less tangible benefits: "Stone edging looks good in all four seasons," says This Old House landscape contractor Roger Cook.
Setting block edging is a one-person project that can be done in a weekend or two, depending on the length of the driveway. If done the right way — with the stones firmly bedded in a thick concrete base for support, and no mortar in the joints, which can become a maintenance headache later on — it will never need any more attention.
On the following pages, Roger demonstrates how to set it and forget it.
A 60-lb. bag of premixed concrete, while convenient to buy, is only enough for a 2-foot-long setting bed. For big projects, it's less expensive to buy bagged cement and a pile of sand. One 80-lb. bag of cement and 200 pounds of sand make a 20-foot setting base. Blend the dry materials first — three shovelfuls of sand to each shovel of cement — then add just enough water to make a good, stiff mix.
Stone Edge, Step-by-Step
Dig a trench 1 foot wide and 8 inches deep along the edge of the driveway. If the driveway slopes, start at the top and work downhill. Toss the dirt in a wheelbarrow and dump it on a tarp. You'll need some later for backfill.
2. Clean the edge
Snap a chalk line on the pavement, just inside the driveway's edge. With a cold chisel and 3-lb. sledgehammer, slice away the asphalt along this line. (Make sure to wear safety goggles.) Trim the soil beneath the pavement flush with the clean edge. Before discarding the asphalt chunks, check whether your town recycles them.
3. Stake a line
Drive two stakes at the edge of the driveway, no more than 50 feet apart. Tie a mason's line between them. Its height above the top edge of the pavement should be no more than half the depth of the stone. (Roger used a 2-inch exposure for this project.) Check this height along the string and adjust it as needed by adding a stake. Lay out the first 10 blocks along the pavement near your starting point: at a corner or the most conspicuous end.
4. Set the blocks
In a wheelbarrow, mix up a batch of concrete. It should be relatively stiff so it doesn't squeeze up between the blocks. Shovel a few inches of concrete into the trench over a 3-foot stretch at the starting point, then use a trowel to smooth out the mix. Now take one block and set it in the concrete, tightly against the pavement and even with the corner.
5. Level the tops
With a rubber mallet, tap the stone's top flush with the mason's line. Bed and even up the remaining stones, one after the other, keeping each one tight against the last.
6. Secure the bases
When all 10 blocks are in place, push the concrete 6 inches up their back sides, then trowel it smooth at a 45-degree slope. Lay out 10 more blocks and repeat the steps.
7. Turning corners
Where the edging turns a corner, keep the stone faces tight to one another. Always end a row with a full-sized stone. If it doesn't fit, use a diamond-bladed saw or grinder to trim the last four stones in the row. Trim them all by the same amount to make the changes in size less noticeable.
When all the blocks are set, sweep some stone dust (available in bulk at stone yards) or ground limestone (sold in bags at nurseries) into the gap between the blocks and the pavement. Don't use sand; it attracts ants. Finally, fill behind the blocks with topsoil and plant with grass seed or cover with mulch.
Belgian block, the generic name for granite cobblestones, comes in three sizes — regulation (or regular), jumbo, and cube — and in four colors: pink, black, tan, and gray.
For this project, Roger used regulation blocks, which measure about 5 by 5 by 9 inches and weigh 20 pounds apiece. You'll need approximately 12 regulations for every 5 feet of edging. They're typically sold by the pallet. One pallet holds roughly 140 pieces this size.
If you need bigger blocks, choose the jumbos (4 by 7 by 10 inches; 29 pounds; 100 pieces per pallet). Cubes measure 4 by 4 by 4 inches. They're too small for edging, but they make fine pavers.