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Arniston House near Gorebridge in Midlothian was designed by William Adam, father of the more famous Robert. It was built by the Dundas family in the first half of the eighteenth century. It is a great privilege as well as a responsibility to be asked to do repair works to a building of this significance.
The estate staff had dismantled one section of the North balustrade, which they had discovered to be unstable. I took each piece in turn and set it out on some carpet on the lead roof and carefully chipped off the nasty hard cement that had been used to reassemble it some time ago.
 Seven of the balusters were broken, and one of the broken off bases was itself broken and could not be reused. I had prepared a new base off site and simply dressed the broken end flat to mate with the new base, checked that the overall height would be correct and then joined the bits up.
As with all the other broken balusters a centre point was found and carefully marked, and a hole drilled into each side of the break. A 4mm brass dowel, was then fitted, and the stones dampened and jointed around the dowels with a very small amount of lime mortar.
I used a mix of 5 parts of fine Levenseat sand to 2 parts of lime, the lime itself being 2 parts of mature putty to 1 part St. Astier NHL 3.5 hydraulic lime. The same mortar was used to bed the balusters and copes, and the balustrade was reassembled. 
The slots and holes that had been cut in the copes for the iron cramps that had originally been used to secure the work were made good where necessary with a Lithomex lime based repair mortar tinted to match the colour of the copes. 3mm thick stainless steel cramps were fabricated to suit each joint. These were set in place with the same mortar as used for building, enriched 10 parts to 1 with NHL 3.5 to create a porous but hard setting grout.
The finial immediately beside the reinstated section of balustrade had also been unstable and dismantled. The lower hemisphere and the collar of the base stone had broken due to the expansion of the rusty iron dowel originally used to fix them. The broken faces of the stone were a light purple and I used Watscliff sandstone as a good match for appearance and hardness and made an exact copy of the bottom half of the finial. Most of the other finials,
four out of six, have been reset at some time due to same problem. I drilled both the trunk of the base and the new stone to take a 140mm long 10mm brass dowel. The finial was reassembled with the same mortar as the balustrade. |
