2torial #0741:
Learn2 Build a Dry Stone Wall (continued)

Calculate your materials

Once you've chosen your stone, it's time to put on your math cap and figure out just how much stone and filler you'll need. Here's how:

• Decide on the wall's dimensions. (If you've already figured the rough size, it's time to get specific.) Measure out the length with a measuring tape. For the height, stay under 2.5 feet (.76 meters)--anything higher could have stability problems. The base should be roughly three-quarters of the height, unless it's a low wall (under 1.5 feet, or .45 meters), in which case it should match the height.

• To find the amount of stone you'll need, multiply height times width times length to get the total cubic area of the wall. Next, divide this figure by 15 to calculate the stone in tons (15 cubic feet of stone is roughly 1 ton, the unit in which stone is sold), or by 4.57 to calculate it in metric tonnes.

• You'll also want filler, or aggregate--bits of washed stone to put between the exterior sides of the wall and below it, for stability and drainage. Aggregate is sold by the cubic yard, which is 27 cubic feet (about 9 cubic meters). The amount you'll need can depend on the type of stone you use, so get the stone supplier's recommendation before you buy (these places will commonly sell aggregate, too). A safe bet is about half of the total cubic feet. Dividing the total cubic feet by 54 (27 times 2) will give you that figure in cubic yards.

If you're wondering why you'd need the full amount of cubic feet in stone, in addition to half in filler, the reasons are stability, selection, and security. First, you'll need a little extra aggregate for the base layer below the wall. Some extra stone will give you more sizes and shapes to choose from, which is crucial to a well-built wall. And finally, remember it's better to have too much than too little.