Hi there to Everyone
I have just sent in my first post to this site much earlier today. Forgive my apparent stupidity, but I prefer the sentiments of The Simpsons to The Waltons and, for today only, I have found myself saying "Doh" far too much!
I hope that I am not the only one who is having difficulties posting a photograph on this site.
I have been asked to provide a word or two on my photograph of 'The Head of Commerce', before it was fully restored. You can see this in the photo gallery, amongst a few others.
Back to the issue. Rather than go on, I thought that I would provide you with an honest, published account (twice to date with good payment made, so ALL COPYRIGHT STRICTLY OBSERVED)
The Royal Exchange - A Case Study
Working in the building conservation industry as a specialist contractor, where much time is devoted to the completion of technically demanding specifications, on time, in a highly competitive market, it is sometimes easy to forget the significant contribution that is being made to the preservation of Britain’s architectural heritage.
Given that the British Museum is still fresh in the memory of professionals who like to see the right job done well, I was particularly pleased to be offered the chance to work on one of London’s other great landmarks, The Royal Exchange.
Built in a bold Classical style (1841-44), the focal point of The Royal Exchange is the west pediment, 35 metres wide and 5 metres high, comprising a detailed frieze sculpture with seventeen statues and miscellaneous objects depicting international trade.
As the Site Manager for Triton Building Restoration Ltd, my role was to supervise a programme of planned external maintenance works to the building, which included provision for a specialist geophysical survey of the statuary, an inspection of over 400 stone roses to the cornice and all essential stone repairs.
No matter how thorough a survey may be from ground level, or even with the benefit of a “cherry picker�, one can never tell just how good the condition of a building will be until a fixed scaffold is erected and there is the opportunity to give it a good shake or even, dare I say it, break a piece off a Grade I Listed building!
Every stone contains some kind of natural defect, which will eventually be exposed as a structural weakness by the constant weathering action of the sun, ice, wind and rain and buildings which are highly decorated afford a more severe test of durability of any given stone; a consequence of the increased surface area presented to the elements.
Some materials are more susceptible to accelerated decay than others, as Charles Dickens once noted when he described the Anston stone used to build the Houses of Parliament as being “the worst ever used in the Metropolis�, having seen the need for constant, expensive repair. In this instance, the magnesian
limestone was full of vents, shakes and vughs, defects which really should have been observed by the Select Committee responsible for selecting the stone.
An architectural contemporary of the Houses of Parliament, The Royal Exchange is built in Portland
limestone, the material advocated by the London Guild of Stonemasons and which had already been used to good effect centuries before, by Inigo Jones, Christopher Wren and Nicholas Hawksmoor, amongst others.
As might reasonably be expected on a building of this age in an exposed location, the extremities of many of the sculptures, such as noses, toes, fingers, hands and feet, had deteriorated, very much like the effects of frostbite. In a few places, the mortar joints were defective and apart from minor repairs to a handful of scrolled corbel brackets, the condition of the Portland
limestone was extremely good. However, a cause for concern was the displacement of cladding panels to the rear of the frieze sculpture and the condition of the 3 metre high statue of “Commerce�, which had been repaired on at least one occasion.
Using the naked eye to determine the cause of the damage, a fracture pattern which bore no relation to the natural bedding and jointing in the stone suggested that the problem could be due to the rusting of ferrous cramps and reinforcement rods, a frequent cause of structural failure in stone. It is extremely difficult to predict when a building component will fail, and at what point previous attempts at repair become uneconomic and when working on a Grade I Listed building, every attempt should be made to diagnose the problem without resorting to exploratory cutting out works.
A detailed survey of the background cladding panels with a basic metal detector, including those that were obviously fractured, produced point readings at regular intervals. To the statue of Commerce, however, the scan proved inconclusive, with metal discovered throughout the upper parts.
A good twist of the head of “Commerce� proved that initial suspicions were well founded and, once the head was carefully removed, a rusted square section iron dowel was clearly visible. When oxidised, iron can expand up to six times its original volume, a force which no stone can withstand.
With no option but to carefully cut away the neck and shoulders, to reveal the extent of the damage, twelve pieces of stone were set aside for potential re-use. Given the indeterminate results of the initial geophysical survey, it was necessary to undertake further investigation using Ground Penetrating Radar, a technique used to precisely locate the position of metal reinforcement within the statue.
Having established that the ferrous dowel extended 250mm into the torso, the next step was to remove this with a slow speed core drill, using water to lubricate the bit and minimise potentially damaging vibrations.
Once the full extent of the damage had been determined, the possible options for repair were proposed to the client. Although technically possible for the existing fragments of stone to be pieced together with a combination of stainless steel dowels,
epoxy resin and lime based mortar, a technique commonly used for in-situ repair, this would be at very best, a short term solution. On this occasion, the most cost effective option was to replace defective material with matching Portland stone.
Using the retained fragments and a detailed photographic record for reference purposes, roughly carved pieces of Perryfield Whitbed Portland stone, selected from the Triton Stone Library, were prepared in the workshop before being taken back to site for re-fixing and final finishing in situ. In keeping with good building conservation practice, original masonry was used where practically possible.
As with any repair, attention needs to be given to preparatory work. With the pattern of fracture shearing through the left shoulder, it was necessary to cut out a piece of the undamaged statue to leave a stable horizontal plane on which the head and shoulders could be securely re-bedded.
With two large pieces of the original masonry fixed back in place with stainless steel pins on a bed of lime based mortar, the stone was grouted using white Portland cement and the head of Commerce re-bedded with a 600mm stainless steel ribbed dowel, before pointing with lime mortar.
As for the damaged cladding panels, although rusting ferrous cramps were identified as the cause, full investigatory and replacement works were considered to be beyond the scope of the contract and repairs were kept to a bare minimum. All rust to the exposed cramps was hammered off, before treatment with a phosphoric acid based rust inhibitor and zinc phosphate paint. New 40mm thick Portland stone panels were then pieced in, with a batted finish to closely match the existing.
On completion of the contract, the project administrator from DTZ Debenham Tie Leung commented “I want to say firstly how great the stone repairs look on the West Elevation. The workmanship is really good and the client’s money well spent. Well done�.
I hope that completes a good introduction to myself.
Have a look at
Glowing Edges Designs
There is enormous scope to turn these images into architectural glass, ceramic tiles for walls and floors etc etc
Linear Mode
