TYPE OF STONE
The original quarry, Cromwell, from which the stone was sourced when the Piece Hall was built in the 18th century, was unable to supply stone in sufficient quantities for the project. As a result, the fine-grained carboniferous sandstone used was sourced from Lower Edge Quarry, supplied by Rand & Asquith (Aceblade), which is just over the hill from the Cromwell site. This means that petrographically, and microscopically, it is an excellent match.
METHODOLOGY & FIXING METHODS
The Piece Hall is of international architectural importance: such a special place demands a high quality and expert finish. Repairs were required to be meticulously carried out, and of the highest standards of workmanship. Calderdale Council worked closely with Historic England and LDN Conservation Architects to agree the scope of essential works. As work progressed there were challenges along the way, as would be expected taking into consideration the age and complexity of the building.
All repair work had been assessed by the architects. Stone Edge used its knowledge and expertise, working closely with LDN throughout, to confirm the most appropriate type of repair in every instance and taking great care at all times. Any adjacent sound areas of the building’s fabric, including other stones or columns, could not be damaged whilst carrying out the repairs. Stone Edge’s expert masons undertook the careful removal of stones for salvage or repair using appropriate traditional hand-tools of the correct size.
Where stone replacement was required the meticulous methodology was adhered to. This included extensive propping and protection of the historic building to allow for the installation of new and measures to allow the building to settle back. Traditional lime mortars were used to exact specifications, to ensure the most appropriate match and final finish.
When complete replacements were carried out, there was no requirement for additional fixings. Once in place, every replacement stone was individually handtooled, using the same techniques and fire-sharpened chisels as would have been employed by the original stone masons. This ensured the new stones had a uniformity and harmony of finish when compared with the old.
For time-worn stone, sections were replaced with new using indenting techniques. The old stone was removed using hand tools and mechanical grinders and stainlesssteel pins introduced into the sound stone remaining. New stone from the quarry was prepared to the required size and profile, using hand tools and mechanical grinders, with holes for the pins. Lime mortar was used to bond the stone together and point the cuts in.
Other types of repairs, however, did necessitate the use of a variety of fixing methods.
Stone Edge used a range of fixings, which included:
- Grade 316 austenitic stainless-steel fixings
- 08, 10, 12 16mm threaded rod
- 6mm x 60mm smooth dowels
- Frame cramps in cavity wall installation
- Hilti Hit HY270 resin
- Lead packers
- Slate packers
Heavy plant was used to install large stones, such as columns, lintels, jambs and floating flagstones. The plant included rubber duck excavators, telehandlers, forklifts, roustabout lifters and specially designed hydraulic grabs working together with rotators. Often, it was down to the ingenuity of the site team, using simple techniques to move large stones, inch by inch, over a day with timber wedges, packers, ropes, pulleys – and a little brute strength. Sometimes, the old methods are the best.