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Beech Stone Cleaning And Restoration

Dunderave Castle, Inverary Argyll, PA32 8XQ

Nature & History of the Project.

The Macnaughtons proudly owned Dunderave Castle in 1598 and remained in use until the early 19th century, but by the 1880's it was derelict although the masonry "shell" remained in fairly sound condition. 1912 saw the restoration of the Castle by Robert Lorimer which has been progressed to the present day with the owners since 1989, Dr. Stephen and Sandra Joffe, careful not to alter the history or heritage. The Castle sits directly on an outcrop of land which means it has magnificent views up and down Loch Fyne. However, the elevations are also exposed to any storms that march through the Loch, some in excess of 140 mph. Dr. and Sandra Joffe have previously had restoration works completed, but they have not always been successful. One recommendation was to apply what appears to be a 2 pack epoxy polyurethane coating to stop the ingress of water through the facades. However, water ingress did not stop and infact appeared to make it worse as condensation could not escape and the freeze/ thaw action began to craze the surface allowing moss and algae to form in the joints .


The first task, therefore, was to remove the coating to allow the walls to "breathe" and let any retained water escape. Whilst scaffolding was being erected it was decided to form a 3 m high ground level "evaporation" zone to the two main elevations by removing the coating. Prior to the removal of the coating tests were carried out to formulate the best way to expose the stone substrate. Trials were carried out using "Intachem" paint removers, 90 deg hot water at a pressure of 500 psi and a low pressure abrasive system using Bengal Garnet at 5 bar. In this instance the abrasive system was by far the most thorough and effective way of removing the coating, algae and lichen. As soon as the coating was removed the stone joints turned dark as condensation began visibly trickling out. Once the scaffolding had been erected the coating was removed and a closer inspection of the fašade was carried out. It became apparent that in certain areas the pointing was too hard thus not allowing any expansion / contraction of the stonework. This lack of slight movement meant cracks formed in the pointing and had damaged some of the stonework. Upon further inspection it transpired that the flaunching to the top of the chimney stacks, fillets at the junctions of all roofs to chimneys, parapet walls or any other upstands were of the same hard mix, thus giving rise to the possibilty of leaks, major or minor The coating was removed and any residue of algae etc was treated with a biocide. All cracked or loose pointing, all fillets to the roof areas (whether cracked or not), any stones in the fašade or any damaged roof slabs were all carefully removed by hand. (When the pointing and roof fillets were removed there was evidence of major leaks as moss and algae had grown in the joint behind and where the stones were severley weathered they also had an algae and moss growth) The stone joints were also treated with a biocide, but some stones in the fašade ( and some roof slabs ) were too eroded and were replaced. Where the roof fillets had been, the gap between the roof slabs and parapet / chimney was filled with a lime based mix, an 18mm rebate was formed and code 6 or 8 lead (dependant on position), plus wedges, was installed and pointed in a lime based mix. As the quarry for the stones was now extinct we were given permission by Dr.Joffe to dismantle walls that were obsolete, in the copse on his land, and indent reclaimed stones within the fašade. The pointing of stonework generally and leadwork was completed using 1 part HL 3.5 : 4 part local brown sand : 1 part sharp sand. After making samples of slightly different mixes non of them dried to a matching colour, texture etc to the existing. It was then thought that when the Castle was originally built the sands were probably not brought in but were taken from the beaches of the Loch (plus solids we don't use now). So sand was taken from the beach, washed and dried and mixed in and the colour, texture and visually was exact. So, with the knowledge of Dr.Joffe, surface sand was removed from the beach, thoroughly washed and dried and used in the pointing. All the chimney flaunchings were removed (they also had algae and moss underneath),treated with a biocide and reflaunched using the same lime based mix. The Main Hall chimney had a specially made cowl fitted to stop rain pouring in but still allowing enough draw in the fireplace to keep the fire going and also to exhaust the fumes. Drips were re-formed in the stone lintols of the windows and doors that had weathered away over the years. The windows and doors were repainted in an oil based paint. Once all the facades had been restored they were washed down and treated with a micro-porous impregnation system which has not altered the surface appearance ( Prior to the Easter period a substanatial amount of scaffolding was dismantled leaving the main elevations exposed to the elements. Over the Easter period the Castle was hit by high winds and heavy rain, but whereas in the past major leaks had occurred, the housekeepers informed us that everywhere was dry ) More Projects


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