The restoration of a Derbyshire town house


Property Remedial Articles - Olympic Construction

Olympic Construction was contacted by the owner of a stone built town house in the Derbyshire town of Glossop who found the information on the Heritage and period properties page of our website. The reason for the original call being dampness affecting the internal elevation of the lounge.

On inspection it was discovered there were a number of defects which were presenting a risk of water ingress into the front elevation of the property, this most obvious one being the incorrect installation of the gutter and rainwater down pipe, this was a simple fix and was undertaken the flowing week.

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Photographs showing the damage and decolouration to the front elevation of the property due to the incorrect chemical cleaning system used.

The more serious issue being the damage and defects noted to the Ashlar stone dressed walling to the front elevation, this had been subject incorrect cleaning works by unqualified contractors. Chemical cleaning methods involve applying a substance to the face of the stone, which then reacts with dirt and buildup of deposits on the stone, due to contamination from the environment.

The chemical is then removed, along with the soiling normally by water cleaning, both alkaline and acid chemicals can be applied as liquids, gels or pastes, depending upon the system that is used. These being less physically damaging to the stone than the cruder forms of mechanical cleaning, chemical techniques which have often left a permanent legacy on the affected building by changing its colour, or by leaving residues in the stone.

This was the problem with this property in Glossop as it was constructed of a porous sandstone. No matter how good the attempts are to “rinse off” the chemicals, some residue will always be left behind, resulting in the opening of the pore structure of the stone. As a result of the effects of gravity, rinsed-off chemicals are also likely to remain in higher concentrations on the lower parts of the treated wall and in projecting architectural details. The long-term effects of chemical cleaning can include, irreversible bleaching or staining, leading to changes in the building’s appearance and the stone’s colour leaving unsightly white deposits (efflorescence) as a result of residual deposits (salts) being drawn out of the sandstone to crystallize on the surface, erosion of certain natural minerals leading to ‘pitting’ and changes which can also accelerate the stone decay.

The surface of the stone had been changed, into what can only be described as honeycomb, resulting in water being absorbed into the stone structure and migrating into the inner face of the wall, resulting in damage to the applied plaster finish, a number of incorrect repair applications had been attempted by contractors who were not qualified or had no understanding of what the issues were or what was required to correct the defects to the stonework, to ensure the wall structure was again made watertight.

In this situation the only effective means of repair is to remove the face of the affected stone work, back to good stone, unfortunately in some cases the stone was so badly damaged new stone sections need to be installed, the problem with this form of repair is it will remove the original detail from the stonework.

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The face of the stonework to the front of the whole property was spun back by 10mm by our English Heritage registered stone mason, the defective stone was cut out and new stone installed, the removed detail of sparrow pecked punching and drafted margin edge detail had to be cut into every stone by hand, the wall was then repointed with 3.5 NHL Lime mortar to match the original mortar compound.

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The photographs above showing the finished front elevation, which was water tight and has restored the property back to its original glory.
Our client was good enough to post a comment on the Trustatrader website, in relation to the works,
He really knows what he’s doing, is very thorough and clean in his quotations as to what work needs doing. A wonderful job with no hidden extras sprung on me, very pleased.”

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