Working in bad weather and above a busy departure lounge with poor access, Mitie Roofing, winner of the UK Roofing Awards 2017 Liquid Roofing category, still met the client’s exacting requirements.
Gatwick Airport’s North Terminal has undergone a huge modernisation programme to its facilities, including a new £21m departure lounge to create more space for future growth and offer more retail and restaurant outlets. Mitie was tasked with replacing failing flat roof to the highest standards of quality within tight timescales in an operational airport that sees 150,000 passengers pass through the terminal buildings every day.
Complexity
The roof area was packed with 30 items of plant, five large air-handling units, an adjacent glazed façade and 36 large plinths with their own steel work, cable trays and pipe supports. This made installing a tapered scheme and applying coating to all the plinth details hugely challenging. This was further complicated by a central rain screen façade separating the roof, hindering access and making the space extremely confined.
All plant had to first be disconnected and raised so that the prefabricated roof sections could be installed before recommissioning. To prevent disruption to the numerous retailers, much of this work had to be completed overnight within a four-hour window. Before priming with Kemperol D, the existing lead skirts, cover flashings and associated cementitious insulated upstands from each large support plinth had to be removed.
Challenges
A significant challenge was access through a single 40 m scaffold gantry route via the North Terminal plant room. This access route was used for the removal of 400 sqm of slab and 2,100 sqm of insulation, plus all deliveries, which were transported up and down the five storeys using the goods lift. Deliveries were also required to be booked-in and permits issued for access and security checks.
The low 250 kg/m2 roof loading meant that the removal of the slab and 250 tonnes of ballast had to be painstakingly managed, with the aid of a suction excavating machine. Installing a tapered insulation scheme on such an intricate roof was particularly testing, while significant time was spent adjusting, chamfering and checking varied levels of the existing deck to successfully deliver the scheme without standing water.
Workmanship
In addition to a leak-free installation guaranteed for 25 years, with zero defects and no standing water, the installation also had to be flame-free, odour-free and environmentally friendly. To meet the requirements, Mitie Roofing worked with the principal architect at project inception to develop the best solution.
Kemper Systems was identified as a key supplier, with full daily Inspection and Test Plans (ITP) and Inspection and Test Records (ITR) developed to run in conjunction with the manufacturer’s standard QA procedures.
Spot sampling of the existing Vapour Control Layer (VCL) was used to check for potential uplift of the bond, with failures cut out and repaired before installation of the new self-adhesive VCL. This was further bonded with hot-air welding of all side and end laps.
Because the installation of the liquid plastic waterproofing system was largely carried out during the winter period, careful laser and digital monitoring of deck and air temperatures was carried out respectively and logged using the ITR.
Installing the waterproofing around the numerous items of plant and steel work required maximum focus on quality, with each phase of work inspected by Mitie Roofing, before inspection by the manufacturer and the client’s senior team.
Mite Roofing says:
This project demonstrates first-class delivery within a live airport environment, which required total dedication, focus and excellent communication. With a commitment to quality and safety Mitie Roofing completed this intricate project on time and within budget.
About Mitie Roofing
Mitie Roofing has full regional coverage, with the ability to provide a local service from local offices, with locally-sourced labour. We offer a high-quality, efficient and competitively-priced roofing service, from the initial survey and consultation, right through to completion and handover. We have an outstanding record on health and safety as well as all the accreditation we need to deliver our service safely and to the highest standard.
