Photos by Ken Ige, Star-Bulletin
Strings suspended from a wooden frame help a worker
for Nisa Contractor build a blue-rock wall, above.

A wall of stone adds stability
and beauty to your fortress

By Tim Ryan
Star-Bulletin

hat homeowner hasn't coveted those rugged, fortress-like lava rock walls that surround so many homes in Hawaii?

Not only are they expensive -- as much as $300 a cubic foot by one professional's estimate -- but these status barricades take skill to build and lots of muscle. You'll be lifting rocks as big as 24 inches in diameter and as heavy as 30 pounds.

But let's say you just want a little wall, like 3-feet high, and you want to do it yourself. Living in an area where stones are abundant makes the job a whole lot easier, though finding large stones at least 6 inches in diameter can be tough. You may have to order a truckload from a mason supply company.

A low stone wall adds an attractive, rustic touch to a yard or garden, said Todd Black, a landscape architect with PBR Hawaii. The building process is relatively simple, Black said, but be warned, lifting and hauling stones is not for the feeble.

Before you even get started, Black advises do-it-yourselfers to don steel-toed shoes and gloves and, when lifting heavy stones, "bend your knees, keep your back straight and let your legs do most of the work."

Photos by Ken Ige, Star-Bulletin
Stone walls are popular with homes in the
hilly parts of Makakilo.

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Remember, Black said, what you are really doing is putting together a puzzle of your own making.

"Make sure you get the right rocks and take your time fitting them together," he said. "Make very sure pieces fit together. Don't get lazy and just shove a lot of small (rocks) together. You'll pay for any impatience in the long run."

A low stone wall can be more than just decorative, Black said.

"Though a slope can provide visual interest in an otherwise flat yard, it can also be difficult to landscape because of soil erosion from water runoff."

One solution is to terrace the site by building some sort of retaining wall that prevents erosion and at the same time creates a raised area for planting, he said.

Even building a low wall involves some heavy-duty landscaping, with lots of hours of sweat equity, Black said.

To begin, you usually lay down a foundation of concrete so the stones are set on a secure footing, Black said. That means digging a trench 6 to 12 inches below grade where the wall is going to stand. Then pour in about 4 inches of concrete, using the dirt sides as the form.

"A concrete foundation is not essential for a low, not-mortared wall, but it will provide tremendous stability," Black said.

If you don't want to pour concrete, Black said you must tamp the soil thoroughly to compact it into a firm surface.

Photos by Ken Ige, Star-Bulletin
Saisa Nisa aligns rocks along a wall.

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"When loose soil settles, water can move the earth and the wall will crumble, especially if it's retaining anything," he said.

A stone wall can be random, using uncut, roughly dressed or dressed stones in uneven courses, or it can be regular, with stones fitted tightly in level courses, Black said. Stone walls can be laid with or without mortar.

Some masonry builders suggest that a do-it-yourselfer's first wall be a dry stone wall -- no mortar -- no more than 3 feet high. Dry stone walls are more flexible than mortared ones, generally need no concrete footing and require an excavation of only about 6 inches.

Higher walls might require reinforcing bars, Black said.

"If you build a wall in the Hawaiian dry-stack method, it's more like a puzzle and may take more skill than most people possess," Black said. "The trick is finding boulders that basically lock together and hold the wall."

Black also suggests looking for stones with solid bases, flat tops and one or more straight sides. For wall ends and corners, you'll need a supply of stones with two flat sides that meet at close to a right angle. You can also break stones to get the angle you want with a sledge and a mallet, Black said.

"You start with what we call 'man stones,' which is what one man can lift, usually a rock about 24 inches in diameter," he said. "The big stones are always on the bottom."

Gravity holds well-built dry-stone walls together and pulls apart poorly laid ones, Black said.

And though large stones will speed a project, handling them can be exhausting, Black said. He suggests trying to stick to those that weigh less than 30 pounds.

Built correctly, a rock wall should last several generations, Black said.

If you're successful with a dry stone wall, you may want to try a mortared one. The mortar improves the bonding between the stones, permitting higher walls and vertical faces. But the same principles for working with gravity apply: Mortar is not as durable as stone. When it fails, gravity and friction take over.

"If you use mortar, try to hide it between the rock and behind, so it doesn't show," Black said.

And because a mortared wall is relatively inflexible, to minimize movement, build it on a concrete footing, Black advised.

How to do it yourself Suggestions from architect Todd Black: Place the course on firm, level ground, using stakes and level lines to guide the construction. Place larger, more irregular stones on the bottom, digging as needed. Tilt the stones slightly toward the center of the wall. Black suggests tapering the faces of the wall inward a minimum of 1 inch for every 2 feet. Fit each stone so that it contacts the adjacent stones in as many places as possible. Place the stones "one over two," staggering vertical joints by laying one stone over the joint between the two below. For stability, make the wall at least two stones thick. A wall 3 feet high should be about 18 inches thick. Turn corners by overlapping long and short stones from each leg in alternating courses. These stones tie the two legs together. At wall ends, finish each course smoothly by laying stones that are reasonably smooth and flat on the ends.