King Solomon Academy

King Solomon Academy

King Solomon Academy, just off the Edgware Road at Paddington, was built in the late 1950’s as the Rutherford School.

It was designed for the London County Council by the award winning Festival of Britain architect Leonard Manasseh and at the time the Teaching Block was considered innovative with the early use of precast and prestressed concrete in this country.

The school was Grade II* listed in 1997 and was closed in 2006 for subsequent refurbishment and formation of the King Solomon Academy.

The uncoated precast concrete mullions to the Teaching Block were in reasonable condition for their age with the need for concrete repairs, cleaning and application of a migrating corrosion inhibitor (MCI) and clear coating to provide protection to the reinforced concrete.

The requirements of English Heritage together with the needs of the Structural Engineer had to be balanced to produce:

  • A structurally sound repair system.
  • A repair mix similar to the original concrete design in order to replicate the weathered faces of the mullions.
  • A mix suitable for hand application.
  • A mix matching the existing in colour once cured.
  • A clear matt coating.

Initially sample mullions were cleaned by water jet and a range MCIs and clear coatings were applied for approval by English Heritage.

This was followed by the forming of concrete repair samples in moulds using a variety of hand applied concrete mixes incorporating both OPC & white cement together with SBR in varying ratios.  A number of these were then rendered with a variety of sand/cement mixes for a thickness of 3mm and then prepared to expose the aggregate to simulate 50 years of weathering

All samples were treated with MCI and clear coating systems for final approval by both the Structural Engineer and English Heritage.  In all 16 different samples were produced to accommodate the combinations of mix design and coatings.

The works to the façade were accessed from a combination of cherry pickers and scissor lifts to allow for a full visual inspection, hammer test, cover meter survey and carbonation depth testing. The mullions were cleaned followed by the concrete repair and render treatment that were hand rubbed in places to achieve a matching finish.  This then followed by the application of the MCI and clear coating.

Once the glazing had been replaced and the existing frames prepared and painted the building was back to the condition that reflected its grade II* listing.

Heathrow Express

The Heathrow Express is a high-speed rail link giving passengers the fastest journey time of 16 minutes between Heathrow Airport and Paddington Station in Central London.

The service was opened in May 1998 and runs from Paddington following the Great Western Main Line for 12 miles where it enters a five mile tunnel near Hayes.

From here it continues under the airport to 2 stations, one serving Terminals 1,2 & 3 and a second four miles away beneath Terminal 4.

Upon completion of the tunnelling works in early 1997, we were invited by Laing Baily Joint Venture to carry out trial works and offer budgetary advice for the application of a decoration render to the platform tunnel walls at the station at Terminal 4.

Flexcrete Ltd had previously designed a decorative render, Monolevel MF, for application on the Jubilee Line.  At Terminal 4 this was modified to match the decorative precast GRC wall panels by incorporating a blend of selected micas from international sources producing a highly striking sparkle effect, quite unlike the traditional drab finishes associated with protective renders.

A standard of finish was established during site trials following which we negotiated the subcontract for preparation and application of the render to the curved concrete walls to the platforms, walkways and concourses.

It was important to give full access to the curved walls for the tradesmen to apply the render.  This was achieved from specially designed multi decked mobile scaffold platforms with wheels on both the platform and track.

Initially surface laitance was removed from the concrete by strictly controlled wet blasting.

Working between the cast in V-joints and for the full circumference of each platform wall the 2 to 3mm thick render was then applied by hand in 2 or 3 passes and finished with a damp sponge to fully reveal the translucent mica inclusions.

This process was repeated in the passenger cross tunnels and concourse areas. Dummy joints were introduced to give a continuous finish matching the adjacent newly installed decorative GRC panels.

Over 8,500m² of Monolevel was applied over a 6-month period with a team of up to 10 skilled tradesmen producing the aesthetically pleasing finish required.

The Friends Meeting House

The Friends Meeting House

The Meeting House is a grade II* listed non-denominational meeting place situated at the University of Sussex. It was designed by the eminent Sir Basil Spence, the celebrated architect of the post war era. The structure, which is a circular 2 storey building with a conical roof, was completed for dedication in October 1966.

It is constructed primarily from large board-marked reinforced concrete blocks, laid in a staggered formation with multi-coloured stained glass filling the gaps between blocks.

The internal concrete faces, which have been left uncoated since construction, had become stained over the decades. In an attempt to clean the walls we carried out cleaning trials using a number of techniques including the use of dry-ice pellets. This method leaves no blast media upon completion as the pellets evaporate upon contact with the surface that is being treated.

This approach was felt the most appropriate within the building where the use of grit, sand, chemical or water blasting techniques would be disruptive and totally inappropriate.

The external concrete surfaces had previously been repaired and coated by us in the early 1990s as part of a maintenance package and were in need of refurbishment.

Subsequently we were awarded a subcontract for treating both the internal and external surfaces of the building.

All external concrete was pressure washed and a minor amount of concrete repair carried out before the application of an elastomeric coating at high level and anti-carbonation coating on the remaining areas. The sealant within the parapet was also replaced as part of the works.

Repair mortars, coatings and sealants were manufactured by Fosroc Limited, with the works being completed during the university summer holidays when the campus was least busy.

Colchester Castle Museum

Colchester Castle

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.

Cobden House and Gloucester Avenue

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.

Chelsea FC

Stamford Bridge

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.