Start with the wisdom of an old stoneworker’s adage: “One stone over two, two stones over one.” In other words, stagger the seams of your rock wall, and if you’re using fieldstone, take another bit of classic advice: “Pick stones that nest.” That means choosing rocks with contours that hug each other as closely as possible where they meet. Make sure to check local regulations before you begin, confirming that your plans comply. Since mortared stone walls are typically heavier than mortarless dry-set walls, building codes often include specifications for the footings. (Mortared stone walls need a concrete footing to prevent cracking due to frost heave.) Many require the use of reinforcing rod. There may also be also regulations requiring professional engineering, depending on the height of your wall. Allot roughly two to three days to lay a 3x10-foot wall. But take your time: Stonework is a matter of continual trial and error, testing to see which combination of stones works best. Make sure to prepare the site and order your stones in advance, then get ready to start stacking. Editor’s tip: You may need a little help holding up the stones. Irregular stones are bound to leave gaps that cause the stone to tip before you can mortar it. Cut a few small wooden wedges before you start laying the wall and keep them close. As you work, insert them in the gaps to help the stone stay level. Mortar around the wedges and remove them once the mortar is set. Then fill in the holes left by the wedges. Fill in the core and mortar the stones. Then dry-fit the next row and reset it, checking the batter as you go. (This is the subtle angle in a rock wall, with the top slightly narrower than the bottom to prevent toppling.) If you’ve made your mortar a little wet for ease of application, don’t set more than three courses a day—the weight of the stones will cause the courses to sag before the mortar sets. Lay bondstones every third course, at roughly 4-foot intervals. When the mortar begins to set up, stop laying stone and finish the joints. Cap the wall with a course of flat stones large enough to cover both wythes. When you mortar the capstones, do not finish the joints. Brush them flush with the surface of the capstones to keep water from collecting and freezing there—it could split the mortar or the stone. Editor’s tip: As you strike the joints, you’ll usually find some places between stones that need extra mortar in order to be even with the rest of the joint. Use a mortar bag to fill them. Mix mortar slightly wetter than you would if you were troweling it, fill the bag, and squeeze the mortar into the gaps. A bag is easier to control than a trowel and reduces the amount of mortar spilled on the wall or ground.
