Put Your Driveway into Overdrive
Rough cobblestone and thick pavers distinguish a long stretch of asphalt
This blacktop leading to the house looked the same as the side roads in this rural area. The owners wanted something that would define the entrance to their driveway. Working from a design by landscape architect Elliott Brundage, This Old House landscaping contractor Roger Cook and his crew spent two weeks laying roughly 15 tons of granite to create a 16-by-33-foot decorative apron. "We installed a piece of hardscape that announces the driveway," Rogers says.
Roger's techniques for laying out, setting, and cutting stone can apply to smaller decorative insets and paving projects of any kind, from patios to walkways.
Nearly as hard as diamond, granite is practically maintenance-free and impervious to damage.Colors: Gray is most popular, yellow is ideal for beach properties, pink suits urban settings, and "black goes with everything," says David Croteau of Stoneyard.com.Sizes: Cobblestones come in cubes (4x4x4 inches), regulations (4x5x9 inches), and jumbos (4x7x10 inches). Pavers are sized in 6-inch increments, from 1-by-1-ft. squares to 2-by-3-ft. rectangles. Anything bigger is a custom order. Patio pavers should be at least 1½ inches thick. If cars will be driving on them, they should be at least 3 inches thick.Finishes: Smooth granite is slippery when wet; outdoors it should be thermaled, flame-heated with a torch until the smooth layer pops off. The tumbled finish on cobblestones and split faces on some slabs offer traction. Costs Cobblestones cost about $6 to $10 per square foot. Regulations are the cheapest. Pavers run $15 per square foot.Weight: One jumbo cobblestone weighs 36 pounds. An 18-by-24-by-4-inch paver weighs 170 pounds. Hiring a pro to move it adds add $10 to $15 a square foot.
Where the apron will meet asphalt, Roger made a clean cut through the blacktop with a gas-powered cutoff saw driving a 16-inch diamond blade. After prying up one edge with a chisel-tipped iron bar, he called in the heavy machinery to peel up the pavement. The asphalt is carted away to a stoneyard, where it is recycled into base material.
An apron needs a 10- or 12-inch base of well-packed gravel to support the stone and the weight of any car passing over it, and to drain away water that could cause frost heaves. In this case the asphalt already had such a base, saving Roger days of excavation and tamping. To guide the stone layout and establish its finished grade, he anchored a bright orange mason's line down the center of the apron. This line remained in place for the entire project.
Starting at one corner, the crew bedded black Belgian blocks vertically, in what is called the "sailor" position. Each stone was set in a couple inches of an 8:1 mix of stone dust and portland cement, which is flexible enough to handle freeze-thaw cycles. A few whacks with a rubber mallet adjusted the stone's depth to the mason's line.
Two rows of sailor-set black cobblestones established the edges of the border. In between, the crew set gray blocks face down (the "shiner" position) in the stone-dust/cement mix. They troweled more mix between the stones until it came within 2 inches of grade. To keep the cement from staining the stone, they sponge-washed it with water.
Roger had to trim all the 4-inch-thick pavers at the end of each course so they'd fit against the apron's slightly tapered sides. For every other row in the field, he also cut a paver in half to create a staggered running-bond pattern. He marked the cuts with a crayon, then ground through the granite with two passes of his 7-horsepower cutoff saw. Water poured from a bucket kept the blade cool and the dust down.
Once the cobblestone border turned a corner, Roger had a starting point to begin installing the field of pavers. After installing a mason's line to guide the placement of the row, first Roger and his crew spread the setting mix 2 inches deep.
Then they laid the 170-pound slab a half inch from its neighbors.
Finally they set and leveled each stone with a mallet, using a wood timber to cushion the blows. Roger then checked the paver's face for level in two directions—left to right and front to back—before continuing to the next piece.
The stone-setting mix needed a day to cure, then the crew filled the joints with polymeric sand, a material laced with plastic binders that glue the sand grains to each other. After sweeping a 1-inch-thick layer into the joints, they tamped it down with a spray of water, which activates the binders. Another layer, dampened with more water, filled the joints. Two days later, the joints had hardened and the apron was ready for its inaugural drive.
Polymeric sand. This low-maintenance polymer/sand blend forms a hard joint that won't let plants or ants get through, but it softens when wet, allowing water to drain. It's ideal for walkways or patios made with concrete, brick, or natural stone pavers, as long as the joints are ½ to 1 inch wide and at least 1½ inches deep. After 10 to 15 years, joints should be power-washed and refilled.Stabilizing Sand. This green product uses plant fibers or tree sap to firm up sand or stone dust. Should it ever crack, it rebonds to itself after it gets damp. Organic sand is easier to remove than polymeric sand, which helps when replacing damaged pavers. Life span varies, depending on movement and amount of moisture, but it should be maintenance-free for two to three years. At that point, you just add more of the same material. Sand-joint stabilizers. These acrylic- or epoxy-based liquids improve the elasticity and water resistance of existing sand- or stone-dust joints, as long as they're less than ½ inch wide. Also seals porous materials, like brick, but it will darken and create a sheen on any surface it touches. Sand-joint stabilizers last 5 to 7 years.
Elliott Brundage, the landscape architect, designed this apron's rustic black-and-gray cobblestone border, which sets off the austere smoothness of the three paver panels. "I wanted some contrast in the cobblestones to give interest to the design," he says. As a practical matter, Roger made sure to pitch the apron slightly to the left (1/8 inch per foot) to encourage runoff into a drainage retention area. Maintenance for the apron will be minimal because granite is so durable and the polymeric-sand joints won't wash away or grow weeds.