Safestore, Battersea

The Safestore self storage facility is located in Battersea in south London and was originally constructed as a depository in 1901.

Following the successful completion of external repairs to two other Safestore sites in Islington and Edgware, we were awarded the 21 week contract for the repairs and refurbishment of the front, rear, flank ends and internal structural elements together with waterproofing to the roof.

Due to the close proximity of the railway line at the rear of the building and the requirement to keep the building in operation with as short a programme as possible, a combination of scaffold fans, temporary suspended electric cradles and abseil techniques were used to access the facades.

The faces of damaged brickwork were repaired using Remmers colour matched Restoration Mortar and where severely damaged, individual matching bricks were replaced.  Cracks were repaired by resin injection and installation of Helifix HeliBar, helical bar reinforcement, followed by extensive brickwork repointing.

New movement joints were created in external solid walls by cutting vertically and then installing horizontal sleeved HeliBars across the newly formed joints.  The joints were then completed by sealing with a polysulphide mastic.

The reinstatement of the details to the damaged dressed stonework was also carried out by ‘dubbing’ with a polymer-modified, structural repair mortar and completed using the appropriate Remmers colour matched mortar. Rendered bands were decorated using external grade masonry paint.

Concrete repairs were carried out within the penthouse structure using Fosroc Renderoc, pre-bagged, lightweight repair mortar, where soffits had failed due to the expansive corrosion of the buried filler joists, caused by long-term water ingress through the failed roof covering above.

To prevent further water penetration from the roof, Sika LPL’s Decothane System, a glass fibre reinforced liquid roof membrane, was applied to the roof areas. Once completed a Single Point Guarantee, provided by the manufacturer, was issued to the client providing assurances they required for the building’s continued serviceability.

Whilst the above works were being carried out the client also took advantage of having the steel framed windows refurbished and fully redecorated and any broken glass replaced.

Metropolitan Wharf

Metropolitan Wharf

Built in the late 1940’s, the concrete wharf structure on the north bank of the River Thames adjacent to the famous Prospect of Whitby Public House in Wapping was showing serious signs of distress.

Working with the consultant John Foreman and Partners we provided technical and budgetary advice for the client, Capital and Counties, for repair and corrosion control of the structure following which we were awarded the contract.

Restrictions imposed by the Port of London Authority, the Environment Agency and local residents, compounded by the range of tide levels, resulted in detailed planning of all operations.

Working within limited working hours due to the tides, scaffolding was erected from the foreshore below with the working level boards being tied down to prevent flotation at high tide.

Following a thorough clean of the concrete, on site investigation confirmed that the major problems related to the beams and columns within the tidal zones and the underside of the precast planks supporting the slab above.

Fosroc Ltd prepared the repair and protection specification which consisted of high build, hand placed polymer modified repair mortars and free flowing micro concrete.  This was followed by the application of 2 coats of a penetrating hydrophobic silane-siloxane to protect the structure from attack from chloride ions and water intrusion.

To prevent the formation of new corrosion to the reinforcement in areas adjacent to the newly repaired concrete, Galvashield XP sacrificial anodes were installed and incorporated into the repairs. Once installed, the zinc core corrodes preferentially to the surrounding rebar providing ‘Cathodic Protection’ and therefore preventing incipient anode formation.

The contract was completed within the 18-week programme using over 11.5 tonnes of hand placed mortars, 10 tonnes of micro concrete and over 750 sacrificial anodes.

Basement Leisure Complex

Leisure Centre Basement Pool

An inspection of the concrete soffit above the suspended ceiling of a leisure complex swimming pool found severe corrosion of the reinforcement and extensive spalling of the concrete.  The complex was housed in the basement of a converted building in North London and had structural steelwork installed some years ago during the conversion which had corroded with the resultant rust delaminating in layers.

Following a full concrete survey by a specialist consultant, we provided methods and budgets for the client and the  Main Contractor and were able to negotiate the subcontract for the repair.

With the pool close for in excess of 6 months, the client required the remedial works and fitting out completed as soon as possible to limit revenue loss.

Weekly planning meetings, led by the hands-on client, were held with the all the specialist subcontractors and designers.  These were essential as limited as-built drawings and details were available.  A repair plan was agreed at negotiation stage and final details agreed as the areas were opened up.

The severity of concrete degradation resulted in the need to install major propping prior to removal of defective concrete.  Over 1200 sacrificial anodes in strings of 10 were   then   installed   to the soffit and beams to control corrosion together with monitoring anodes and boxes.

Preparation of the surfaces by open grit blasting was followed by repair using 7 tonnes of hand placed mortars and 30 tonnes of spray concrete.  A cementitious fairing coat and elastomeric coating were applied to both the repaired and existing concrete to enhance protection to the structure.

The structural steelwork was also cleaned by grit blasting followed by the application of a high performance coating system.

Strict controls were put into place to reduce the risk to the health and safety of the operatives.  These ranged from forced air to control dust and labour rotation for limiting exposure time to vibration from power tools.

Upon completion of the structural repairs, a high performance ceiling was installed to provide a moisture and temperature controlled environment for the structure with access made available to check the anode monitors.

Despite the many unknowns at planning stage the project was completed on time.

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.