Projects

Blair Castle South Roof


Blair Atholl, Perthshire


In Autumn 2014 the Blair Charitable Trust asked Jonathan Gotelee to inspect the South Roofs of the Castle because there were obvious problems with water coming in, not simply from leaking lead work or isolated roof failures, but because the roof slating more generally was letting significant quantities of water through causing the sarking boards underneath to be almost permanently wet.

The roofs in this area form the second phase of David Bryce's Baronialisation of the castle and were completed with the building of the new Entrance Hall block, in 1869. Most of the structure and walls date from this period.

Inspection showed that the slates were the original Craiglea Perthshire slates but had been taken off and re-dressed sometime after the First World War and relaid on a lime:hair slurry, they were therefore very small and without sufficient lap to keep increasing rainfall out of the roof. In addition it was obvious that many of the sloping valley gutters were now undersized and regularly overflowing in heavy rain, often by as little as half way down the gutter and that poor abutments between slating and stonework or harl was allowing water into the wall cores and blowing the harling off the wall's fronts.

Research in the Castle Archive revealed a number of things; that much of the roof had been re-laid in the 1920s as a part of preparing it for leasing to a tenant; that the most expensive item on the original 1869 bills for the work was for Ordinary Portland Cement for harling and that there were photographs taken by Valentines of Dundee in 1870 of the newly re-built Castle. The research helped in a number of ways. First of all we knew that the roof had to be roofed with new slate as the area was too large to replace with larger second-hand slates. The photographs showed that the original roofs were remarkably smooth and consistent, quite unlike their more romantic appearance in 2015 and much as we knew the roofs would have to look when we replaced the slating with new Cumbrian Burlington slate . We also finally had a proof that Bryce had decided to use the new material Portland Cement in the harl for the castle as an effort to prevent water getting in to the walls. This had been our suspicion for some time and the root of many of the castle's problems, as for example at Baron Maule's Room Roof.

The repairs carried out have required careful thought, detailing and skill to execute and Bruar Construction's team have, as usual tackled them carefully and diligently. Each of 4 circular turrets has a curved lead rhone at is base which needed a steel tube former manufacturing to allow the gutters to be formed before lifting them to the roof level. Also, Bryce's abutment details and rainwater management needed to be significantly improved for current rainfall levels and made easier to maintain without altering their appearance significantly. Finally we had to find methods to let water that had got behind cement harl out from behind it without wholesale removal of large areas of harl and its replacement with a lime based harl. We have done this by providing a better head seal to as many walls as we can, by removing cement harl from the rear of parapets and replacing it with a lime based harl and on cement harl areas by using bell cast render stops at the base of the harl above drips and string courses. The render stops provide a protected air gap at the base of the wall area from which water can evaporate should it become trapped.

Once it was decided entirely to re-slate almost one half of the Castle's high level block the Trust's brief for the work was "We want you to be the man who stripped Blair's roofs of failing slates and returned it to a state Bryce would have envied". We have only been the conduit for this work between a brave client and a careful set of craftspeople and hope the results last well beyond the 50 years the original nailing did.

We were delighted to welcome the 2016 Society for the Protection of Ancient Buildings (SPAB) Fellows and Scholars to the site during the course of the work

Design Team


Architect: JGA
Structural Engineers: Elliott & Co
Quantity Surveyors: Thomson Gray
Contractor: Bruar Construction and Restorations
Selected photographs courtesy of Blair Castle Archive

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