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Special Structures (continued)

To build a rock wall, excavate a footing in soil or to solid rock. The footing should be insloped to match the designed batter angle and deep enough to support the foundation tier of stones (these are usually the largest stones in the wall) for the full width of the tread. Ideally, the footing is dug so that the foundation tier is embedded for the full thickness of the stones (Figure 63).

Image of crib wall construction
Figure 63—Rock placement and batter is
critical on the first courses.

Ideally, the stones should weigh at least 20 kg (45 lb). At least half of the stones should weigh more than 60 kg (130 lb). The ideal stone is rectangular with flat surfaces on all sides. The worst stone to use is rounded like river rock.


In reality, you have to use the rock available. Small crib walls can be successfully constructed from smaller rocks. The key is the foundation platform and he batter. Remember to save some big rocks for the top course where you need them for capstones. A final point—most rock can be improved with a few good blows from a rock hammer. Placing the rock on dirt rather than another rock before striking will help ensure it breaks where you want it to.
 

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