Perhaps the most challenging part of building a stone wall is fitting irregular shapes and sizes into a pleasing and effective pattern. A carefully fitted stone wall has a natural sculptured beauty that few other materials can match. Almost any type of stone that is available in quantity can be used. The easiest stones to trim and face are stratified rocks, such as sandstone, limestone, and shale. However, they are not recommended for use in winter climates, where the combination of excess moisture and low temperatures tend to crumble the layered composition of such rocks. The most durable rocks are composed of granite and basalt. Their very toughness, however, makes them harder to break and chip for fitting purposes.
Stone walls can be built with or without mortar. Naturally, the use of mortar will produce a more durable structure, but if stones are properly fitted together, their weight and balance alone are enough to hold them together.
TWO TYPES OF STONEWORK
There are two broad classes of stonework -rubble and ashlar. Rubble masonry is composed of uncut stones, fitted together in their natural state. Ashlar masonry is built with cut stones, laid in fairly regular courses. An amateur may find the ashlar stone easier to use because the regularly shaped stones can be laid in place with less juggling than is required for irregularly shaped rubble stones.
THE QUANTITY AND SIZE OF STONE REQUIRED
The amount of stone required for building a wall is normally figured in tons; the area that a ton will cover will depend on the type of stone used. Your dealer will quickly figure the needed quantity if you provide him with the total cubic wall area.
Be sure to choose a variety of sizes in the type of stone you select; usually the face area of the larger stones should not be more than 5 or 6 times the face area of the smallest stones. The larger stones should be laid in the lower levels, the smaller stones in the upper. Large stones can sometimes be broken to size while you are working.
TOOLS AND EQUIPMENT YOU WILL NEED
The most important tools and equipment you will need are a hammer for chipping stones, a sledge hammer for breaking stones, a container for holding mortar, a spade or shovel for digging the foundation trench, a wheelbarrow for carrying materials, and a trowel for spreading mortar.
In order to keep your work aligned, use mason’s twine or string to mark the boundaries. Also use a level for checking alignment as the work progresses.
AMOUNT OF MORTAR REQUIRED
Because of the numerous and irregular size of joints to be filled, stonework requires a relatively large quantity of mortar. There is no sure way of estimating the amount needed to build a complete wall; however, one solution is to lay up a small section, figure the amount of mortar you used, and then compute the quantity needed for the rest of the wall.
The recommended formula for mortar is 1 part cement and 3 parts clean sand.
USE A FOUNDATION FOR ADDED STRENGTH
Any masonry structure should have a foundation of stone or concrete set well below the surface of the ground. Where the climate is mild, a foundation of 10-12 inches depth is usually sufficient for a 3-foot wall. Make sure the ground under the foundation is firm and compact.
A dry wall-one that is assembled without mortar-does not require a deep foundation, even in regions of severe climate. The wall may topple or list a bit, but is easily repaired when good weather comes along.
Concrete foundations are easy to pour and are relatively inexpensive. If a stone foundation is used, it should be laid with mortar, and have time to dry completely before the actual wall construction is started.
PROCEDURE FOR SETTING THE STONES
Before you begin construction of the wall, make sure that you have enough rocks on hand and placed where you can easily reach them as you work. If you have a choice of sizes and shapes, you will be able to keep your pattern interesting. Try placing several stones in a small section before mortaring to see if the pattern is the one you desire. Then begin the construction. Here are some helpful hints to guide you:
1. Remove all dirt and lichen or algae from the stones with water and a stiff brush. (Do not use a steel brush as it may produce rust stains.) Let rocks dry before mortaring.
2. String a guide line to keep the face of the wall flush. Place the first row of stones so they do not jut beyond this line.
3. To give the wall the proper slope inward, nail two boards together at the angle desired, for checking as work progresses. Your wall should slope 1 inch in every 24 inches of height.
4. Offset vertical joints at every course to assure a proper bond. Also set some stones with their long dimensions at right angles to the face of the wall to add strength.
5. Make sure that all joints are completely filled with mor-tar. Make the joints as thin as possible by filling empty spaces with small chips of stone while filling with mortar.
6. After laying one section, use a stick to rake out the joints on the facing before the mortar sets. The deeper the rake, the better the shadow effect. Brush off excess mortar with an old broom before it completely sets up.