Tuesday, 14 September 2010

The rocking stones of Surrey

Regional variations in building methods are becoming rarer as uniform materials and techniques take hold. Of the three key cost variables in UK building - labour, materials and transport - it is now the first two that are the most expensive and the last that is relatively cheap, leading to a state of affairs where developers source the cheapest materials and put them up as quickly as possible in a way that is standardised across the whole country. In the Georgian period the opposite was broadly true: transport was hugely expensive but labour and materials were cheap, so for example local stone was used and numerous skilled craftsmen were employed to erect it.

And so it is now chiefly in historic buildings that regional variations are evident, as here in Albury Park near Guildford in Surrey, where a technique known as galletting, or the insertion of smaller stones into mortar, is shown to good effect. This can be purely ornamental but in the main its purpose was practical: it was used where the only stones available were hard and had irregular edges, so that when one was laid on another the stones were unsteady and a large gap was left between them. Because the stones were hard, it was easier to fill the gaps with mortar than reshape the stones to give them a flatter edge. But the mortar was less durable than the stone; and the stone was non-absorbent, meaning the mortar adhered badly. The result was weakness on two fronts. To help overcome this, small wedges (often chippings from the masons' workshops, but in this instance pellets of local ironstone) were inserted in the mortar to add strength and counteract the natural rocking between the stone courses.

The practice, which in England is confined to areas where it was structurally necessary (Norfolk and the Weald, which lacked building stone), became known as galletting, after the French word galet for water-worn pebble. The technique dates back to mediaeval times and continues even today for ornamental purposes. Here at Albury, a Tudor house, the present galletting dates from a substantial remodelling by Pugin in the 1840s.

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