Prior to any works being carried out by us at the school we provided budgetary and programme advice to the school’s building surveyors for the concrete repairs and anticarbonation coatings to all 4 elevations of the 8-storey main block. Independently the surveyors obtained budgets for the replacement of the existing crittall type windows from SEH Commercial, a national glazing company.
Subsequently we were awarded the contract for both repairs and window replacement to the South Elevation of the block, the first of four phases that were awarded over the following four years.
Like many projects carried out in our schools, programming issues are critical as the works are required to cause as little disruption to the day to day running of the school and often squeezed into school holiday periods. All works were finally agreed to be carried out to a reduced programme of 6½ weeks with scaffolding commencing within an hour of the school breaking up in late July for the summer holidays.
On a rolling programme, scaffold was erected and the building hammer tested and water jetted whilst school staff removed IT equipment from the rooms affected by the works. This was followed by window removal and installation of temporary windows that allowed concrete repairs and anti-carbonation coating works to be completed before the new windows were installed.
The repairs and protection to the concrete were carried out using Fosroc HB25, a high build hand placed polymer modified mortar and Dekguard W, a water based acrylic copolymer white anticarbonation coating.
The fibreboard spandrel panels below each window were cleaned, joints made good and sealed and finally coated in one of the school’s corporate colours.
Internal making good, redecoration of the openings and refitting of blinds was followed by school staff finishing with a deep clean internally and reinstatement of equipment ready for the next term to start in early September. The final scaffold was struck and the site cleared within 2 days of the start of new term as planned.
We were awarded contracts for the three remaining elevations in subsequent years with the major works carried out during the summer holidays. The works to the North Elevation was the most complex due to the requirement to bridge the scaffolding over low level buildings and provide propping within the building.
The river wall on the south side of the Thames between HMS Belfast and Southwark Crown Court has undergone many changes in its history including the demolition of the old pier and raising of the wall height for flood prevention.
The wall was constructed from yellow stock bricks that had been protected by render in places, however due to many years of weathering by the tides the exposed areas of masonry had suffered from loss of pointing and failed brickwork.
Following a survey of an 85m length of the wall, carried out on behalf of Her Majesty’s Court Service by Peter Brett Associates, we were awarded the contract for carrying out repairs under the direction of EC Harris LLP.
The planning for the works had to take into account the effect of the tides and was further complicated by the need to satisfy a number of 3rd parties. These included the Port of London Authority, the Environment Agency, the local authority and the owners of the adjacent areas of land either side of the wall as well as the operations of the Court Service.
Scaffolding was progressively erected along the face of wall, founded on the riverbed and mechanically tied to the wall, with all scaffold boards tied down to prevent movement due to tidal action.
Defective render was removed by use of electric breakers to expose the old brickwork below. Eroded joints were repointed in a fast setting repointing mortar and missing bricks replaced with bricks that matched the existing. Weed killer was applied to unwanted vegetation.
This was followed by preparation of the surfaces by grit blasting to provide a key followed by the application of a spray concrete containing an alkali free accelerator and reinforced with polypropylene fibres. The finish was cut to line and trowelled whilst the excess material was cleaned from the scaffold and riverbed prior to the rising tide covering the work.
Other works carried out whilst on site included:
The Safestore building in Edgware is a large industrial unit comprising a reinforced concrete frame (columns and floor slabs/beams) and brickwork infill panels.
An investigation was carried out by Martech Technical Services to establish the causes and the extent of defective concrete. During this investigation it was identified that the brickwork panels were moving under light hand pressure. After further investigation it came to light that there were no ties between the outer leaf of brickwork and the inner leaf of blockwork in any of the panels.
We were awarded the contract to installed Helifix DryFix remedial wall ties to tie the inner and outer leaves of brickwork together as well as the outer leaf of brickwork to the concrete columns. Specially designed steel wind posts were fabricated and installed at the midpoint of the brickwork panels by our sub-contractor, Artistic Engineering Limited. These were deemed necessary due to the brickwork panels being the largest size that building regulations permit.
In addition to the above issues, the building’s concrete frame was also in a poor state of repair. Following the full site investigation, extensive concrete repairs were undertaken. Furthermore, the concrete frame was provided with corrosion control by the installation of Margel Vapour Phase Inhibitor pellets, a migrating corrosion inhibitor in capsule form, followed by the application of a pigmented anti-carbonation coating.
Additional works were carried out which included the waterproofing of an external staircase using one of Sika Limited’s flooring products and the removal of 2 no. large window sets and replacement with rendered blockwork.
The building remained occupied throughout with the site foreman working closely with Safestore staff and customers as well as the users of adjoining properties.
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.
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.
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.