Tuesday, March 29, 2011

Hand Pitching

This is new section of pitched pathway built in the lake District by professional waller and trail maker Gavin Rose.

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I first met Gavin in Mallorca at the 2007 Stone Symposium workshop in Deia where a large number of enthusiastic students learned to build the unique walls and historic cobbled stone pathways they have there.

Gavin has since been to Canada several times to take our Canadian bridge building workshops in Russell Ontario, Cobourg Ontario and most recently at the DSWAC annual event Rocktoberfest last year where Gavin introduced this method of pitching for the walking surface on Kay's Bridge which we built during the festival.

Here is what Gavin writes about this method.

This style of stone pitching has a long history in the Lake District in places such as slate quarries, where the steep grade of the track required to move material on the fells to lower down meant that the tread needed to be reinforced. In this particular case, a combination of trail bike traffic and water was severely eroding this unclassified road.

For those unfamiliar with stone pitching, one way of describing it is like a single skinned retaining wall with a very low batter i.e. a roughly 6 to one batter as opposed to the more normal proportion of one to six. As the track was lower than the verges on either side a pipe and stone culvert were placed down the middle and the pitching built over the top of it. At certain points in the pitching, water bars were installed to divert surface water run off into the culvert underneath.

To get an even surface I used a a simple technique that I learnt in Mallorca, Spain where pitching has been used for thousands of years. At the start of my pitching, at the down hill end, I placed a board across the road at the height I wanted the final surface of stone to be and placed another timber board cross the road at the other end of were the section of pitching would end - using a spirit level to get each board level. With the two boards in place either end I could then use a third board, with one end resting on the downhill board and the other end on the uphill board to determine the final surface of the pitching in between.

Then it was a case of laying the stones much as you would in a wall - placing them with their length running into the pitched surface and crossing the joins for strength - and using my board as a guide to get the right level(much as you would use a string line and frame on a wall to get the correct batter). Once the stone had been laid, gravel was meticulously worked into all the voids between and under the stones, using a stick, to help hold the stones in place.