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Unit 800 Aztec West

Consisting of a series of multi-level octagons, this complex roof needed a long-lasting covering. Following a laborious strip-out, the team had to cut and detail-in multiple mitred hips, along with numerous sumps for outlets, as well as re-clad the building perimeter and five staircases

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Unit 800 at Aztec West is a multi- level office block, offering nearly 7,000sqm of lettable office space over three floors. The existing 4,250sqm roof had reached the end of its useable life so required full replacement. A high performance felt membrane was chosen for its hardwearing properties, needed because the roofs would be regularly accessed for maintenance. Mitie Tilley was contracted to carry out the roof works and the external wall cladding.

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Workmanship

The hexagonal arrangement meant there were multiple mitred hips which had to be cut and detailed in, along with numerous sumps for outlets. Numerous lightning conductor posts that penetrated the roofing membrane, so the team decided to detail these tricky areas with Icopal’s liquid coating sprinkled with mineral granules to replicate the rest of the roof.

A tapered scheme also needed to be designed and installed to replace tapered insulation that had been discovered in some areas during the strip-out. Meanwhile, five complicated staircases with leaking brick parapet walls had to be detailed in plywood, before being felted with external GRP trims to form a full encapsulation.

Build-up

Roof: BMI Icopal Products (Total Torch VPL; 120mm Thermazone; torch-on insulation boards; Total Torch vapour dispersion layer; and charcoal Thermaweld Firesmart mineral cap sheet.

Wall cladding: Kingspan Products (KS900 Optimo; 120mm insulated Quadcore panels with a Spectrum Onyx colour).

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Complexity

The office block’s complicated hexagonal shape and multi-level roof layout presented many logistical problems requiring detailed planning and co-ordination to achieve a high standard of work. The team had to deal with numerous penetrations, including lightening conductor posts, and a laborious strip out of the existing roof, which in places had a build-up of two layers of insulation and cork boarding.

At a glance

  • Project: Unit 800 Aztec West
  • Roofing Awards 2019 Winner: Industry Choice and Reinforced Bitumen Membranes
  • Award sponsor: Sika
  • Location: Bristol
  • Roof Covering: Reinforced Bitumen Membranes
  • Client: London & Scottish Property Asset Management
  • Roofing Contractor: Mitie Tilley Roofing
  • Client: London & Scottish Property Asset Management
  • Main Contractor: Trident Building Consultancy
  • Product Suppliers: BMI Icopal and Kingspan

About Mitie Tilly

An award winning industrial and commercial roofing company, Mitie Tilly is the UK's largest roofing refurbishment contractor with over 30 years of experience.

www.mitie.com