You are here: The Challenges of carrying out restoration work on old structures


As the Statue of Liberty approached its one hundredth birthday the New York Parks Department decided to carry out a refurbishment programme on the ‘stately old lady’.

While much of the proposed work was relatively simple and routine, amongst the challenges faced was the removal of an early application of bitumen to the inner surface of the outer copper façade.

The Statue is constructed of a central double spiral staircase, which allows visitors to climb up to the head of the Statue to a viewing platform which is contained within the head of the Statue. This robust ‘central tower’ forms the core of the Statue’s construction, with ferrous supports ranging in every direction to form an armature upon which the outer copper shield had been attached using brass rivets. Due to the Statue’s position on the edge of a tidal bay, the exposure to a continuous salt laden atmosphere had taken its toll on the different metals.

At the commencement of this electrolytic reaction, a coating of bitumen had been applied to ‘insulate’ the problem. This had initially proved successful, but in time the impact of the bitumen’s prolonged exposure to the elements was causing concern and resulted in the decision to remove and apply further protection.

Seymour Feebach (a highly respected American Engineer) was consulted on this aspect of the work and it was Seymour who contacted me and asked that I visit and advise on a possible solution as to how to successfully remove the bitumen without damaging the historic copper coating. Fortunately I had a good friend who owned a paint stripping company and he mixed a couple of ‘solutions’ which he felt sure would render the bitumen water soluble.

On arrival in New York, I was accompanied by Seymour and members of the New York Parks Department on a visit to the Statue. There is nothing worse than a group standing around watching you work, so I suggested they had a coffee break while I carried out an initial test.

Half an hour later they returned and I was able to show them a section of the copper with all the bitumen removed and the original ‘tooling marks’ clearly visible. The look of amazement, coupled with their elation at having the problem solved for them, was most rewarding, as was my fee!


During an annual inspection of Cathedral’s fabric, it was decided that the historic stonework of The Lady Chapel should to be cleaned. The challenge was to carry out the cleaning of the stone walls whilst protecting the medieval wall paintings at ground level.

Scraping, brushing or any harsh physical contact with the stone was not permitted, so I decided to wash the stone with nothing more than clean cold water, as any chemical additive may have caused a great deal of damage to the stonework. As further protection, a ‘drain’ was positioned above the wall paintings to ensure that in the event of the slightest spillage; this would be caught and diverted away from the paintings.

A certain amount of ‘dust’ was removed from the face of the stone using a hand held nozzle attached to a domestic vacuum cleaner. This work was carried out using only very soft fine hair bristles, this ensured minimal disturbance to the stone surface.

Once the dust had been removed, we started from the top of the wall and worked our way down using a pumped up mist spray to apply a very thin film of water to the face of the stone. Mopping-up with very soft towelling did not achieve the total result we wished, and the remaining stubborn stains would require some form of very gentle agitation in order to be removed.

Enter several hundred very soft toothbrushes, which were used with extreme care to ensure there was no damage to the surface of the stone. A final gentle mist spraying washed away any remaining dirt into the drainage system.

This ‘delicate’ operation provided a very successful outcome, so much so that a few months later we were invited to return to the Cathedral to tackle yet another challenging cleaning problem.


During a particularly cold winter a group of children living near the New Forest were worried that nobody was looking after the wild ponies, after all their own ponies were being well cared for in warm stables!

When their cries for help fell on deaf ears, they decided to take matters into their own hands and very early one morning travelled to Stonehenge (and giving credit for seeking an excellent advertising location) spray painted their message ‘SAVE THE PONIES’ in 5ft high red lettering, one letter per stone at an area where the stones were facing a main road.

As soon as the ‘slogan’ was discovered it was realised that immediate action was required and unfortunately white spirit applied to spray paint acts as binder, in much the say way as it would react with oil based paint, thus making it much harder to remove.

Whilst a number of cleaning companies indicated they would be prepared to consider finding a cleaning solution, English Heritage approached me as I had already provided them with solutions to some other difficult cleaning jobs.

Due to age and exposure to the elements, the Stones had become covered to a large extent in moss and algae, and straight forward removal of the paint would also remove the patina of ‘agricultural growth’ and risk leaving an imprint of the individual ‘ letters’ on each of the affected Stones.

Using a number of different techniques, including an aluminium oxide gun, paint stripper and very fine abrasive equipment, the paint removal was achieved without any marks to the underlying stone.

The next challenge was to restore the many years of agricultural growth. Enter a local farmer who was the source for a rather ‘interesting mix’ of chicken and pig manure and sour milk. This distinctive ‘cocktail’ was worked into slurry, containing just the right ingredients of nitrogen, phosphate and potash to encourage moss and algae and was painted on the Stones. Within five months new growth was covering the treated Stones.

My work is often observed and one day whilst applying the slurry mix I noticed I was being closely recorded by a couple of American tourists, one of which remarked to the other in a rather cross tone “will you look at those vandals over there painting dirt on the Stones”!


Following demob at end of WWII, I became an irrigation engineer supplying irrigation equipment to the farming industry. During this time I recognised an alternative use for ‘mist propagation equipment’ and eventually started my own business, using this innovation to clean stone masonry on historic buildings.
My first commission was to clean the West Front of Wells Cathedral, by a stroke of luck this was featured in the Sunday Times Magazine, resulting in a stream of enquiries and work, which included further historic dwellings in Wells (Vicars Close), South Porch of Malmesbury Abbey, Hovingham Altar Stone, and Sandbach Crosses.
Once established as resource for stone cleaning, I was increasingly asked if I could also carry out repairs, these involved the use of lime mortar, lime plaster and lime render. This resulted in a further expansion of my business, and the birth of the Lime Centre at Morestead in 1979.
In time The Lime Centre grew into a resource providing Consultancy and Training Courses as well as supplying materials, this at a time when there was a growing interest in maintaining the heritage of our many historic buildings both in public and private ownership.
Some of the first people attending my Courses went on to set up similar services in Suffolk, Cornwall & Scotland, we continue to remain good friends today, having acted as referral agents between each other.
Seeing the growth in this type of restoration and the recognition that knowledge of the use and handling of lime should be shared with the building industry in order to ensure future protection for our historic heritage, I founded The Building Limes Forum in 1992 in conjunction with a number of likeminded people. Today The Building Limes Forum has expanded from the UK to have international representation in Canada, USA, Sweden, France & Australia.
My desire to ‘spread the word’ has resulted in undertaking a range of UK and International teaching and presentation opportunities, including the Universities of York, Oxford and Southampton, the US Heritage Group in Chicago, and for International Specialist Skills, two attendances in Australia, including Melbourne University. I have worked with students and apprentices who are taking their first steps in the world of construction, and supported many professional colleagues in their CPD.
Armed Forces Memorial at Alweras - and the new Bomber Command memorial with building about to start in Green Park, London. – retained as a Consultant by Liam O’Connor, Architect for both of these Memorials
Newport, IOW – Repairs to the Harbour Wall in Newport at the head of the Medina River. Due to the tidal situation lime mortar with an ‘accelerator’ was used to facilitate the repair, thus avoiding the need to retard the tidal surge.
Lime mortar has proved particularly successful in Harbour repairs. Historically harbours worldwide have been built using lime mortar, for example the base of Queen Elizabeth Castle in the harbour of the Channel Island of Jersey was constructed in this manner and there the strong tide rises in excess of 8 metres.
House in Time – Folklore in the New Forest records that completing the building of a house between dawn and dusk on one day secured the right to live in it. The fact that my business is based so close to the New Forest means that I am often required to work on older Dwellings which are clearly well built, but obviously constructed in a hurry, this caught my curiosity as to whether we could replicate the ‘dawn to dusk’ build.
Having researched the subject and sourced a team of likeminded enthusiasts, we spent a year mastering techniques and honing our skills. We were supported by a kind donation of an acre of land by Lord Montagu following a recent project carried out on behalf of the Beaulieu Estate, in order that we could carry out an experiment of building a cob house to accommodate a family of nine between dawn & dusk in one day. We selected a mid-summers day to maximise the light and the whole event was filmed for television and I still use the film when teaching cob construction.
Chalk Cob Construction - Due to the large volume of chalk cob dwellings along the length of the Test Valley, I was asked by BBC Schools Broadcasting to assist them in the production of a documentary by visiting Stockbridge Primary School to show young children how chalk cob cottages in their area were built.
Windsor Castle – In 1983 retained to provide stone cleaning to Henry VIII’s Main Entrance to the Castle. Recalled in 1992 to undertake repairs using lime materials to match the original construction, this following the recent major fire which caused significant damage at the Castle.
Globe Theatre, London – provided consultancy, and designed the mortar, for the new Shakespeare Globe Theatre
Houses of Parliament – stone cleaning of the Speaker’s Cloister
Canadian Houses of Parliament – Consultancy for repairs to the historic stone carvings on the Agricultural Entrance.
Coral World Underwater Laboratory in St Thomas, Virgin Islands – Consultancy to provide solution to rusting ironworks in this structure.
Training Courses for the Construction Industry – over the years the Lime Centre has hosted training sessions to the construction industry to provide practical ‘hands-on’ training in the traditional uses of lime within mortar, plaster, render and limewash
My MBE - In 2002 I was Award an MBE in recognition of my work on the maintenance of historic building
In 2009 I decided to step aside from the day to day running of Lime Centre, but unable to completely hang up my ‘hard hat’, I continue to offer Consultancy advice to a wide range of professionals and private individuals to ensure we continue to maintain our many historic buildings.

This paper was written and presented at a CPD Conferences Course by R. H. Bennett M.B.E.
Bob was a much respected long time presenter at CPD Conferences courses, and is sorely missed since passing away in early 2017.