WESTOVER WOODLANDS - CLEAVING SHINGLES
are wooden roof tiles, made by cleaving wood. They can also be used for
wall cladding. In the UK they were traditionally made from Oak (Quercus
robur). In America they are made from Western Red Cedar (Thuja plicata)
and in Eastern Europe, Norway Spruce (Picea abies) is the traditional material.
Oak shingles were widely used in England, and there is archaeological evidence from the 10th Century for shingles up to 15'' (38cm) long. It has been suggested to us that they would only have been produced from the timber in the bottom metre or so of the tree, because this wood is too twisted to work in longer lengths. However, we have found this bottom section of trees to be too twisted even for shingles, and believe that shingles would have been made from better quality timber as it saves time effort and material.
To make shingles, an Oak trunk of at least 40cm diameter is required. The trunk is cut into rounds, 38cm or less in length. We use wedges to split the rounds into 4 or more segments, depending on the size of the round. The sapwood and core are removed with the froe.
The remaining blocks of heartwood will vary in size depending on the diameter of the tree, producing shingles between 10cm and 20cm in width. The shingles are then split off by driving the froe into the end grain of the block, along the medullary rays, producing a cleft shingle approximately 8mm thick. Splitting along the medullary rays helps to ensure that the shingles don't warp, and increases water resistance. One face of the shingle can be cleaned up using a drawknife and shaving horse (sit-on vice to hold timber while it is being worked on).
Historically, shingles were fitted using wooden pegs, which would have hooked over the roof batten. Today copper or stainless steel annular ring nails are used, because they are resistant to the tannin in the oak and therefore will not rust.
Shingles are laid so that at every point on the roof they are three thick, i.e. only a third of every shingle is visible. If fitted correctly an oak shingle roof should last 80-100 years, and we have been told that about 80% of the shingles will be recoverable. The fixings are likely to fail before the shingles.
When using 30cm long shingles it takes approximately one hundred shingles of average width to cover a square metre area of roof.