How Drystone Walls Are COnstructed
I Built this wall in Derbyshire England for my DSWA Level III feature build exam. It passed with decent marks so I can say with confidence that it is an example of a well built wall.
Foundations are dug level into the earth below organic matter and in cold climates below frost heave levels. The foundation stones and subsequent courses are laid with stones length in and packing or hearting laid tight between the two wall faces. Stones are laid with the joints of one course being covered by the next course to bond the wall together along each face.
In a traditional drystone field wall as shown here the two faces are bound together at about knee height with through stones that are packed and fit tightly into the wall. These through stones are places about every 3 feet. And are left protruding from the wall traditionally to prove visibly that they are in the wall. Also in farming areas with limited stone that might be friable or easily damaged it would leave the precious few long stones available untouched by hammer for fear of breaking them into smaller stones that are no longer usable.
The top of the wall is bound together with the vertical coping stones here. Walls can also be capped with flat stones or a cover band. The vertical coping stones serve to bond the wall faces across the wall and as they are set on edge and tightly wedged they also add strength down the length of the wall as well as adding height quickly and creating a more stock proof wall. Although vertical coping is the the traditional aesthetic of field walls and common throughout the UK my clients in the states especially on the west coast are very unfamiliar with the appearance of these walls and opt for flat capped walls instead.
Retaining Walls
Retaining wall are usually built with the same double face structure as free standing walls, with stones laid length into the wall, joints between courses are covered by stones above and below, through stones are still used. Sometimes retaining walls are built as a single face skin with rubble placed carefully behind this face. The larger and longer the stones up to boulder sized stones set by tractor make this style stronger. The risk with the single skin style of building is that the wall does not have a self supporting strength that actually retains the bank rather the bank ends up supporting the stones.
