Working with McLaren as the Main Contractor and with Scott Brownrigg Associates acting as the Architects, Avonside Cobsen-Davies Commercial & Industrial Roofing, served as the Sub-Contractor on this project, which was a multi-disciplined residential development in South London. The project involved 110 new homes, including a mixture of town houses and apartments within blocks of varying levels up to seven stories. Lendlease required contractor design, drawings and the coordination of the design.
Our scope of works consisted of the supply and installation of 5000m2 of Bauder warm encapsulated 3 layer waterproofing system, with laid to falls (LTF) insulation. This was installed to decking, terraces and balconies on a concrete substrate to a multi-level seven storey concrete frame (apartment block) including elements of Brown Roof and paving to high level areas.
Similarly, the same build-up and waterproofing system was installed to roofs and terraces, inclusive of decking to a timber substrate on multi-level 3-4 storey town houses. 1000m2 of Pre-laq (Zinc effect) cladding was supplied and installed to a proportion of the vertical and mansard surfaces of the town houses and over runs.
PCC aluminium copings were supplied and installed to parapets throughout the scheme. PPC aluminium rain water goods were also supplied and installed during the scheme. In addition, a man-safe hand rail system was supplied and installed at high level on the apartment block, fixed roof lights were supplied and installed as were lead works.
We, the Subcontractor, along with our primary supplier, Bauder, engaged with the project design team and the Architect from tender stage through to our initial appointment, to develop the design under the brief to deliver both robust and ‘buildable’ details that met with current regulations, manufacturer’s requirements, the Architect’s concept and, most critically, the client’s expectations.
Throughout these early stages and into the build itself, the design was progressed in accordance with the original design strategy through the regular attendance of design development workshops, whereby a comprehensive review of the various contractor designs was conducted. This review included regular communication between the interfacing trades and accompanying manufacturers regarding the many specific details and interfaces such as: door and window openings/thresholds and brickwork upstands and connections with dividing screens to terraces, which were reviewed to ensure the junctures were seamless and well-considered.
Predominantly led by AGS as a primary envelope contractor, the above was completed whilst maintaining a keen focus on the longevity of the details and ease of maintenance to ensure the finish remains defect free for the duration of the life of the building.
The flat roof weathering comprises of a warm 3 layer felt build-up with LTF insulation and finished with decking to create an accessible roof. One challenge which arose related to the thermal performance of the design in a number of localised areas required an increase in the thickness of the originally specified insulation to achieve the desired U-value however, any increase in the depth of the build-up would have compromised certain details at door thresholds and upstand heights. In order to mitigate the height issue, a high-performance insulate was introduced to these areas to achieve the correct U-value, whilst maintaining consistent levels of waterproofing throughout the scheme.
The major consideration for the installation of Pre-laq sheet to vertical cladding, mansard roofs and staircase overruns was the aesthetic of the finish. The appearance of the vertical lines was a particular architectural concern so each elevation, mansard or over run was detailed for approval utilising differing sheet widths installed in such a manner as to appear to be of a regular size when viewed from various vantage points across the site.
A particular challenge was the design and detailing of the structural fixing and bracketry in order to weather penetrations to the Pre-laq cladding. Both Juliet balconies and dividing screens to terraces required careful consideration to ensure both the rhythm of the standing seams and the clean flat facing surfaces were not punctured with fixing points and supporting elements which would distract the eye.
Due to a fast-moving programme we were often accompanied by neighbouring trades working simultaneously and in close proximity to our works. Our concern with this was the condition of the delicate surfaces, such as cladding and finished waterproofing. To ensure following trades were affording sufficient care and attention when working adjacent to these areas was a constant supervisory challenge. Understandably, McLaren treated such instances as a priority and ensured surfaces were adequately protected once complete and as works progressed behind us and in the vicinity of our installation, until such time as the works were complete and access was subsequently struck.
The Quality Assurance process was understandably a high priority on a project of this complexity. Assisted by the manufacturers and using approved labour with the support of both full-time site supervisors and a project specific contract management team including AGS’s rigorous in-house Quality Assurance process, the quality of workmanship was routinely inspected and reviewed, which involved the signing off of each area sequentially as it was completed.
The site is located in a densely populated residential area, with a school and care home immediately opposite which posed various logistical issues. One of the most significant challenges was a lack of space for both deliveries at front of site and extremely limited storage areas for materials, plant and equipment on site. This, coupled with a quickly evolving site logistics plan, meant that the sequencing deliveries and lifting was a constant management challenge.
Deliveries were required on a ‘just in time’ basis and broken down so each load was specific to a particular block and roof/section. Materials were only permitted on the ground for a limited amount of time before they were lifted to roof level where the completed roof decks were utilised for more permanent storage. Materials were then lifted into place or from roof to roof by means of mobile or tower crane, as required. The storage on the roof posed the addition logistical challenge for us to ensure the sequencing of the works considered the need for storage.
The logistics of the cranes in such instances became a daily challenge, with the very high demand between the various trades.
Daily co-ordination, logistics and delivery plan meetings were held by McLaren to prioritise crane time and review access considerations and the accompanying delivery process throughout the programme to ensure a steady flow of materials to all trades, as required to maintain high standards, keep to schedule and ensure ongoing client satisfaction.
The following measures were taken to maintain Health and Safety:
In addition, McLaren conducted a regular “Mini health checks” initiative checking lung function, blood pressure, BMI, dietary and lifestyle advice and wellbeing clinics were held on site. Front line leadership training days were also run by McLaren.
In circumstances where a concern regarding of health and safety was identified, McLaren would insist upon a whole site safety stand downs with whole site briefings by McLaren.
The project provided the opportunity to accelerate the development of two subcontract operatives to obtain their approved Bauder felt installer accreditation. This was achieved through the guidance and supervision of existing certified Sub-contract operatives who were working alongside the ‘trainees’, AGS Contract Managers and regular inspections from Bauder site technicians.