Colchester Castle Museum is a 1950’s steel framed building housed within the existing walls of Colchester Castle, which is a scheduled ancient monument as defined in the Ancient Monuments and Archaeological Areas Act 1979 (as amended) Section.
Repair works to the roof covering was put out to tender mainly to roofing contractors as the major part of works related to the application of a Sika LPL liquid applied membrane system. Works were also specified for the repair of the concrete elements of the roof lights.
In addition to our concrete repair capabilities, our operatives hold CSCS cards in liquid membrane application and we are an approved installer. We were therefore able to provide a cost effective quotation for all the works.
The contract was required to be carried out in a 4-week period prior to the May Bank holiday weekend whilst the Museum was closed. Detailed forward planning and sequencing of the work together with strict procurement and delivery of plant and materials was vital to meet the very tight programme.
Extensive protection was no required to the listed structure both internally and externally and also to artefacts within the Museum.
Scaffold access towers to the roof were not permitted due to the Castle’s listed status therefore all materials and plant was manually carried up the Great Stairs. Journeys down the stairs for meal and comfort breaks were not wasted as all arisings were removed from the roof at the same time.
Concrete repairs were carried out to the central roof light structure using a polymer modified hand placed repair mortar followed by application of a fairing coat and anti-carbonation coating.
The existing asphalt roof covering was cleaned and over coated with the Sika LPL Gamma 20 system, which offers a 20-year guarantee.
Although additional works were instructed during the contract the works were still completed in time for the Museum to reopen as scheduled.
The benefits of a liquid applied system over traditional asphalt were clearly demonstrated on this project, not only by access issues but also by the reduction of fire risk and potential issues that bad weather could raise.
As part of the refurbishment to meet the decent home standards, two residential blocks in Camden Town, London, NW1 were both in need of external concrete repairs, but in each instance was the consequence of very different problems.
The walkways at Cobden House are of filler joist construction, with clinker concrete infills, rendered and painted. Here corrosion was due to water ingress from above and causing spalling on the soffit surface.
Gloucester Avenue is a tiled concrete frame building. Water ingress behind the tiles had caused the reinforcement within the concrete to corrode resulting in concrete spalling and debonding of tiles creating a hazard for pedestrians below.
At Cobden House loose and defective concrete and render were removed. The steel filler joists were then mechanically wire brushed and primed, followed by the installation of stainless steel mesh. High build polymer modified hand placed repair mortars were used for reinstatement. A thin cementitious filler was then applied to the soffits to cover the mapping effect caused by the removal of defective paint, followed by the application of a pigmented anti-carbonation protective coating.
At Gloucester Avenue traditional concrete patch and girth repairs were carried out where localised spalling had occurred. The tiles were reset with stainless steel pins drilled and resin fixed through their faces with a colour match mortar to disguise the pin head.
There was also a concern about the risk of further spalling where there were no signs of deterioration. The application of a migrating corrosion inhibitor (MCI) to the concrete to reduce this risk would have required the complete removal of the tiles. We were able to offer an alternative to this that saved the client both costs and programme.
Holes were drilled through the face of the tile at 200mm centres along the front elevation of the building and Margel Vapour Phase Release pellets were inserted. These act similarly to an MCI without the need to remove any finishes. Tiles were then repaired similarly to where the steel pins were installed.
After spending a successful season at Chelsea FC’s Cobham training ground carrying out concrete repairs, we were finally promoted to the Premier League to carry out a variety of projects at their Stamford Bridge Ground. As part of the refurbishment of the South Stand, new openings were cut through the concrete walls to give improved access to the stand. Making good to the areas was carried out with structural steelwork and hand-applied mortars.
During the 2005 closed season corporate hospitality facilities in the East Stand were upgraded. We carried out rescreeding for the full width of the stand using site batched mixes incorporating admixtures to facilitate new seating in these areas.
The following closed season further improvement works were carried out at the ground. This in turn resulted in the negotiation of further works to both East and South Stands.
Firstly new flights of concrete steps were cast for the full height of the South Stand as stewards seating was modified. Dowel bars were drilled and resin anchored to the existing terracing followed by casting with prebagged concrete that was mixed adjacent to the pitch and carried up the terracing.
The Home Team dug-out was also upgraded in the same period. Improved sighting of the pitch for both manager and substitutes was achieved by cutting walls and making good with hand applied mortars. In addition, the floor was raised by removal of the existing floor covering followed by recasting of the slab with prebagged concrete laid to falls.
Once the season was underway it was commented upon by Sky TV that whilst the Home dug-out was a vast improvement, the Away team still had to make do. Within a week we were back and the Away dug-out was given the same treatment.
Brooklands is a disused motor racing circuit and airfield just 20 miles south west of London near Weybridge.
It now houses the Brooklands Museum and Mercedes World with many of the old buildings and track reinstated to their former glory.
It was the brainchild of a wealthy landowner Hugh Fortesque Locke-King who, in 1906 during a European tour, decided that Britain needed its own test track if the new motor industry was to compete with the Europeans,
Work commenced in 1906 and in June 1907 the world’s first purpose built motor racing circuit was opened.
Due to the difficulty at the time of laying tar macadam on the steep banks, the track construction consisted of gravel overlaid with concrete in order for the steep banks to be cast in shuttered sections.
In 1937 the Road Racing Circuit, designed by Malcolm Campbell and built of similar construction, was added.
At the outbreak of the Second World War in 1939 the whole site was devoted to the production of warplanes and the circuit’s condition deteriorated during this period. It was finally sold to Vickers-Armstrong for aircraft production and in 1987 it became Brooklands Museum.
The Malcolm Campbell Circuit is classed as a scheduled monument and 100 years after Brooklands opened, we were awarded the contract to repair parts of the concrete track.
Gifford and Partners produced the ‘Specification for Works in Relation to Scheduled Monuments’, which included a performance specification for the concrete based on the original construction. As the aggregate used in 1937 was not available from the original source a similar alternative flint material was found in a quarry in Norfolk. Our concrete technician was then able to design the mix to match that of 1937.
Defective concrete was removed by electric hand breakers and edges square cut prior to the installation of a DPC, spacers and mesh. Due to the small quantities required each day and limitations imposed on the access to the track, site batching was considered the most economical option. Once cast, the repairs were cured with polythene sheeting in accordance with the specification.
The Barbican Estate, built on a 35 acre site between the mid 60’s and 70’s, is a fine example of British Brutalist Architecture with a wide range of exposed aggregate concrete finishes. Surrounding the three concrete residential tower blocks, maisonettes and mews are the Museum of London, The Barbican Arts Centre, Guildhall School of Music and Drama, City of London School for Girls and Barbican Library all set amongst lakes, elevated walkways and gardens.
Due to the age of the structures and reports of a number of visible defects to the concrete, we were awarded the contract to survey the condition of the external concrete facades of the 3 tower blocks by abseil technique. These consisted of visual inspection, hammer testing, carbonation depth and cover meter survey, chloride analysis, half-cell and resistivity tests followed by presentation of an interpretive report and recommendations.
Due to the risk of falling failed concrete, a scaffold protection platform and exclusion zones were provided at the base of each tower whilst the surveys were carried out.
Whilst the extent of defects was being established from the survey and taking advantage of the protection already in place at ground level, we successfully negotiated the next phase of the concrete repair works, completing repairs to within 20mm of the final finish with a Remmers high build polymer modified repair mortar.
In the meantime trials were carried out to establish a finishing material that would be both technically acceptable and also satisfy the requirements of English Heritage and Corporation of London’s Planning Department.
Upon agreement of the specification for the finishes of the repairs, consisting of a colour matched Remmers Restoration, the final phase of the repairs was carried out by abseil techniques and by working from the balconies.
Following the success of the survey and repairs to the 3 tower blocks, we have been awarded a number of further condition survey and repair projects throughout the Barbican Estate.
Built in the 1930’s, the Allington sluice lock gate is the last on the Medway before it becomes tidal. During 2010 the sluice underwent a major refurbishment including new gates, lifting gear and gantry, repairs to the concrete structure, a new fish pass and new disabled access ramps.
Although the sluice is not listed, due to its location adjacent to the Museum of Kent Life, the Environment Agency took a very keen interest in the structure and the refurbishment works. Any areas of concrete that had spalled due to seventy years of weathering were therefore required to be repaired sympathetically to match the existing concrete finishes.
We were employed by the Main Contractor, Jacksons Civil Engineering, to undertake initially trial samples in order to create a repair material that could be applied over the polymer modified structural repairs. This involved design of a range of mixes and bonding primers together with sourcing suitable sands, aggregates and cements.
Following the successful completion of the trials, we were awarded the contract for both structural and cosmetic repairs that were carried out in 3 phases throughout the year.
Upon agreement of the extent of repairs, defective concrete was broken out to expose the corroded reinforcement, which was then prepared and primed using a cementitious coating. Where corrosion to the steel was excessive, additional reinforcement was fixed. Repairs were then carried out using a weber prebagged hand applied polymer modified repair mortar to within 15mm of the original profile.
Repairs were completed by priming with a weber epoxy resin and whilst tacky the application of the approved mix from the trials. Surfaces were then abraded to remove laitance exposing the aggregate matrix to varying degrees. Where appropriate, a soot wash was applied to the finished repair to simulate the result of many years of weathering of the concrete.
Resin injection techniques using weber.tec EP resins were also used to repair cracks where there was no evidence of reinforcement corrosion.