Olympic Construction were proud and privileged to be instructed to undertake the restoration works on the chimneystack of Delph Lodge, Delph Oldham, the property is a prestigious private residence recently purchased by our client who wanted to restore the original chimneys into working order, as part of an ongoing restoration project using traditional construction methods and materials.
Delph lodge forms one of two properties located at the foot of Saddleworth moor, believed to have been constructed in the early 1900, which was later extended to the right hand elevation, the property became a grade II listed building on the 3rd July 1986 (English Heritage Building ID: 212088).
The restoration works to the chimney structure being required to repair the damage as a result of neglect, long term water damage and lack of inappropriate and unsympathetic maintenance of the property by past untrained contractors.
The aim of the works is to reinstate and maintain the original features of the chimney structure, ensuring long term water tightness, where ever possible using the original materials and sympathetically ensuring the building retains its original character.
The original chimney being constructed of Ashlar stone wall, the gutter and eves to the right hand gable elevation above roof height were also in a poor condition, the mortar beds having perished and extensive weed having become established.
A sample of the original mortar was removed and sent for analysis to Conserv Lime Mortar Suppliers & Stone Restoration Specialists, to establish the best mortar match, the nearest mortar compound being ‘Fox Cragg’ lime based mortar, a sample of this to be provided and agreed with the local conservation officer, before works commence. A method statement, building regulations and planning application were submitted and approved, by the local planning and conservation department.
The chimney structure was photographed and measured, before any dismantling works were undertaken, the structure above the roof line was carefully dismantled and the stonework labelled and stored in course form, on a purposely constructed scaffolding at roof level, to ensure correct reconstruction with the same materials where ever possible.
OPC render and pointing had been applied at some point to the external elevation of the chimney, during the original inspection a section of this was removed, to establish the construction and condition of the wall structure below, this was found to be of the same stone construction as the chimney and was found to be in a poor condition to the area exposed. It is proposed to remove the OPC render and leave the stone exposed following reconstruction, as we believe, this was the original construction.
On opening up it soon became apparent the stonework was in a much worse condition than was previously thought, due to the long term effects of the sulphur gases and ammonium from the long term burning of fossil fuels, resulting contamination of the masonry.
When coal or coke is burnt it produces two main by products, soot and smoke, soot is a black carbonaceous solid and is primarily carbon, but it contains hydro carbons which in turn contain ammonium. Ammonium is a byproduct of coal and coke being burnt. When organic matter, coal or coke, containing nitrogen is burnt ammonium is formed.
As the smoke rises out of the combustion, this smoke contains a sulphur gas, water vapour is always present in flue gases, which contain sulphur oxides and tar acids, as the flue gas pass up the chimney and reaches the upper areas of the chimneystack these form as condensation which attack the stone and mortar, resulting in the masonry crumbling and having to be replaced.
The internal ceiling level was the original lath and plaster with an ornamental plaster frieze mold this limited the level of which the stone work could be dismantled, ideally a further meter of stone should have been removed, to get past the last area of water damaged stone, but we had to reach a compromise and causing any damage to the ornamental plaster frieze mold was out of the question.
Our highly skilled English heritage registered stone mason Rob, worked the stone by hand to reconstruct the chimney structure and over a period of four weeks the chimney structure was restored to its full pride and joy, with new lead work installed to prevent water ingress into the roof structure and the formed stone gutter lined with new lead, the upper gable pikes were lime rendered and the chimney flues topped off with new pots, as unfortunately the original pots were crazed and cracked which prevented them being reinstated.