Shell Tower

Structural Renovations Shell Tower

Structural Renovations have recently been carrying out waterproofing works in various locations within the Shell Centre in Central London.

Our works have involved controlling water ingress within the basement and lift pit areas of the main tower.

The 27 storey tower and 3 (now demolished) 9 storey wings were constructed between 1957 and 1962, on part the site used for the Festival of Britain. At the time the tower was the tallest building in the UK and the largest office building, by floor space, in Europe.

Our first phase of works involved pouring a new screed, laid to falls, within a double width lift pit using Flexcrete Fastfill repair mortar, modified with kiln dried quartz sand. The screed and 150mm of the adjacent walls were then waterproofed using Flexcrete Cemprotec E942, a cementitious waterproof coating, prior to the lift engineers reinstalling the lift buffers and rails.

The second phase of works to 2No. adjacent lift pits was based upon a bespoke waterproofing solution designed by Parkinson VTC Ltd. The works involved the installation of a wire mesh box around both sumps within the lift pits, prior to the installation of a 400mm thick layer of 10mm aggregate, to act as a soak away. A 450mm thick layer of Flexcrete Fastfill modified with 10mm aggregate was then installed over the soakaway. The screed and 150mm of the adjacent walls were then waterproofed using Flexcrete Cemprotec E942.

The limited space on site and strict delivery periods meant that up to 4 tonnes of material were being mixed and laid by hand each day.

A major redevelopment of the area, involving new office, retail and residential space has transformed the site and 1,700 Shell staff, who were temporarily relocated to Canary Wharf, have moved back to inhabit the main tower.

Ronald McDonald House, Southampton

Ronald McDonald House, Southampton

Ronald McDonald House Charity (RMHC) is an independent charity which aims to provide free ‘home away from home’ accommodation at hospitals across the UK enabling families to stay close to their child and maintain a degree of normal family life.

The new Southampton Ronald McDonald House houses 53 bedrooms to support families with children being treated at Southampton Children’s Hospital and Princess Anne Hospital.

As well as the 53 en-suite bedrooms, the House has communal living facilities including kitchens, lounges, playrooms and a laundry room. This enables families to stay close to their child and maintain a degree of normal family life.

We were awarded the subcontract for the supply and installation of a Sika Liquid Plastics Ltd designed built up warm roof system to the main roof and inverted roof system to terraces at 3rd floor of the new building.

Over 650m² of the Warm Roof System was installed which consisted of a vapour control layer bonded to the metal decking followed by the installation of cut to falls Decotherm Insulation. This was then followed by a carrier membrane and then finally cold liquid applied Decothane membranes reinforced with Reemat fibre glass matting.

Up to 150m² of the Inverted System was installed which consisted of Reemat reinforced Root Resistant Decothane applied directly to the concrete terrace slab followed by Eco Inverted Roof Board and a filtration layer in preparation for the terrace landscaping contractor.

As we are a Sika Liquid Plastics QA Approved Contractor, the project was regularly monitored by one of their field technicians throughout issuing inspection reports, providing confidence to the client that the works are being carried out in accordance with their specification and finally issuing appropriate guarantees.

The benefits of the Cold Fusion Bonded Built-Up Roof and Inverted Roofs Systems can be clearly demonstrated as:

  • Cold applied – no hot works issues
  • Seamless
  • Excellent thermal & UV stability
  • Fast cure
  • Root resistant where required
  • BBA accreditation
  • Guarantees up to 25 years

HTC Building, Slough

Salamanca in Slough is a five/six storey office block and the UK Head Office for HTC Europe Co. Ltd. The existing flat roof single ply membrane had started to break down and was in need of replacing. The main roof was generally flat with a number of smaller roofs over the lift shaft and staircases together with a significant amount of plant and pipework.

A specification was prepared by Sika LPL for over coating the existing membrane with their Decothane Omega 15 liquid applied system following which we were awarded the sub-contract with main contractor Construct Design Associates Ltd.

Existing falls were checked and where lacking, drainage channels were constructed within the original roof finishes prior to the application of the Omega 15 system.

Working alongside the main contractor, the new membrane was applied in phases to accommodate the installation of the new drainage channels and removal and subsequent reinstatement of paving slabs and pebbles around the plant room. Pipework supports were temporarily lifted and reinstated in order that a seamless coating could be applied.

The specification for the main roof included for an application of a biocidal wash and power wash followed by an embedment coat of the liquid applied one part air cured Decothane incorporating Reemat Premium followed by a further coat of Decothane in a contrasting colour.  Upstands were coated using the Decothane Detail Coat.

Vertical surfaces were terminated by either termination bars or sealant beneath the existing cladding and lighting conductors tapes refixed using self-adhesive clips. The paving slabs and pebbles around the plant room were reinstated on a Filtration Layer to assist in drainage in these areas.

The insulation was also replaced on one of the small roofs prior to the application of the Decothane coatings using a Sika LPL Vapour Control Layer, 130mm thick Decotherm Insulation Board and self-adhesive Carrier Membrane.

In total 2,000 litres of Decothane products were applied successfully with Sika LPL issuing a 15 year guarantee for the client.

The Marnham Building, Mill Hill School

The Marnham Building at Mill Hill School was refurbished as part of a major project being carried out at the school by Mansell. The basement of the building had damp problems with the floor slab, the previously painted brick walls and the concrete filler joist soffit below an external pedestrian walkway. The refurbishment of the area was planned to provide a future teaching facility.

Following opening up of the soffit and investigation we were awarded a design and build contract for the repair and strengthening of the defective filler joist steels and concrete surround. Steel joists were grit blasted and 55m of weber.tec force carbon fibre reinforced plates were bonded to the underside with their EP structural adhesive.

Repairs were completed with weber.cem hand applied polymer modified repair mortars. The external walkway above was treated with a Tor coating to provide a waterproof non-slip membrane.

Grit blasting techniques were used to remove defective coatings from the basement walls, to etch the glazed brickwork beneath and to also prepare the floor slab prior to the application of a waterproof membrane.
In addition a chemical dpc was injected to the internal walls using Remmers Aida Injection Cream and defective pointing made good with a polymer modified repair mortar to provide a suitable background for the waterproof render treatment.

15,000kg of Weber Motex Dry-rend waterproof render, consisting of bonding coat and 2 further coats to a total of 12mm, were applied to the prepared surfaces with a fillet and mastic detail at the floor junction.

Finally the prepared floor was treated with 2 coats of RIW Toughseal and a self-levelling screed to protect the membrane.

The Main Contractor’s finishing trades then completed the conversion to classroom conditions with new blockwork and plaster walls and joinery works.

The Main Contractor’s finishing trades then completed the conversion to classroom conditions with new blockwork and plaster walls and joinery works.

Safestore, Edgware


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.

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.