Take a scenic drive through the back roads of New England and you will inevitably spot some of the 240,000 miles of stone walls built by 19th-century farmers trying to delineate their land. You may not have a large plot to mark off, but your patios and flower beds are still deserving of a border, and one that doubles as a place to sit down will make your landscape all the more enjoyable. But no need to dig up the yard looking for rocks like the Yankee farmers had to. As This Old House senior technical editor Mark Powers shows here, a wall built from cast concrete blocks made to look like stone is just as beautiful and much easier to build—especially when your "planting season" is confined to the weekends.
How to Build a Sitting Wall
Friday: Lay out the length and shape of the wall.
Saturday: Dig out the area and put down the base layer.
Sunday: Build the wall and set the capstones.
Lay Out and Excavate the Area
At least half the depth of the wall's first course must be buried for stability, so you need to dig a trench before stacking the pieces. Allow for at least 1 inch on either side of the blocks, which you will backfill to keep the wall from tilting as the ground settles. Once you've laid out the trench, a level line acts as a reference point against which to check the depth of the trench. Using stones placed at the two ends of the wall as a guide, map out the width and shape of the trench. Add at least 1 inch on either side of the stones. Drive a stake at each end.
String a Line Level
String a line level on mason's line and stretch it between the stakes. To keep the string from shifting, notch each stake and hook the string in the notches rather than tying it; that way you can unhook the string and resecure it as needed when you dig.
Dig a Trench
Using a spade and starting at the low point of any slope, dig a trench at least 6 inches deep or until you reach beyond the loamy topsoil to the lighter-colored soil beneath. Measure off of the level line to keep the base of the trench level as you excavate the area.
TOH Expert Tip: Have a wheelbarrow or tarp handy as you dig to help you cart away the soil while protecting the patio or lawn.
Lay the Base
Create a strong, tightly packed base for the stones with a crushed-rock-and-stone-dust mix known as paver base. Put down the base in layers so that you can pack it well, building it up until the depth of the remaining trench is about half the thickness of your stone. Shovel 3 inches of paver base into the trench.
Use a Hand Tamper
Using a hand tamper, compact the base. Measure the distance from the base to the level line to make sure the base stays level. If necessary, pour additional layers of paver base and tamp each one until the surface of the base at the low point of the slope is half the depth of one block, plus 1 inch, from ground level.
Shovel Stone Dust into Trench
Shovel 1 inch of stone dust into the trench. Spread and level the stone dust by pulling a spade over the uneven surface. Check that the finished depth of the trench with the base and stone dust is equal at its shallowest point to half the thickness of one stone.
Lay the First Course
A level and sturdy wall all depends on the positioning of the first course. A first course that tilts will tilt the block stacked on top of it, and one with gaps will throw off the rest of the joints. If there's any slope to your area, begin to set the stones from the high end of your trench and build up the low areas to avoid having to remove any stone dust.
Set the first stone centered between the sides of the trench. Using a 4-foot level, check the stone running from side to side, front to back, and corner to corner. Using a rubber mallet, tap the stone to set it. Place the next stone. Set it with the mallet, and check that it's flush with the adjacent stone and level in all directions. Continue setting the first course in this manner until you reach the end of the wall.
Backfill the Gaps
Using a spade, backfill the gaps on either side of the stones with extra stone dust and a layer of dirt. Step on the dirt to pack it in place, being careful not to dislodge the stones.
TOH Tip: When setting a stone, butt it against the adjacent stone, then drop it straight down so that you avoid dragging the stone dust and pushing it into the joint.
Cut the End Stones
To give the wall strength, you need to stagger the joints between courses. So the second row of the wall should start with a half stone to offset the alignment of the joints. Using a mason's chisel, mark and score every side of the stone at the point where it will be cut. Create a small channel along the score by chopping it out at an angle, side to side, using light taps on a wide mason's chisel.
Cut the End Stones
Holding the chisel perfectly vertical at one end of the score line, strike it with a maul to split the stone. Use the claw end of a brick hammer to clean off any uneven pieces along the cut.
Build the Wall
A comfortable sitting height for a wall is 18 to 24 inches, including capstones. Most cast concrete stones are heavy enough to stay upright without help. But for safety's sake, you should glue down at least every other course—and certainly the capstones—with construction adhesive made for stonework.
Using a caulk gun, apply masonry construction adhesive in two lines on top of the first course of stones. Set the second course on top of the first, making sure to stagger the joints.
Stack the Courses
Continue stacking courses until the wall is a few inches from the desired height. Lay down two beads of masonry adhesive on the last course, and set the capstones in place. Turn them perpendicular so that they overhang the sides of the wall to create a finished top.