Scope of works would include; licenced asbestos removal, party wall hand separation, robotic demolition, mechanical demolition, ground and basement excavation, temporary works, waste removal and site clearance. The site would be tightly confined within a small area with the retail units adjoined to live buildings to the north and east of the site and pedestrianised high street to the south and west. There was a small courtyard for delivery access to the rear of the units. The construction mix of the buildings consisted of brick and block walls with timber and concrete floors. The roofs of each shop were set at various levels. There was a large concrete canopy located in front of the central shop. The site encircled a chamber to a live storm drain, this would have to be maintained and protected throughout the works and would have to be encompassed within the new design. Consideration would need to be given to the environment, members of the public and surrounding businesses that were in close proximity.
Solid hoarding and scaffolding was first erected to the front facades of all three units forming an ‘L’ shape surround. All retail units were soft stripped of shop fittings and fixtures ready for asbestos removal and demolition. AIB located to the front of the entrance and canopy of the centre unit was removed within an enclosed and controlled asbestos enclosure. Works were notified under an ASB5 and removed by Lawson Environmental (part of Lawson Group) as an approved licensed contractor.
The next stage required investigation works to ascertain the formation of the current construction in order to safely deconstruct the building. All investigation works were carried out by hand.
Vibration monitoring equipment was installed adjacent to the party walls, this remained in place throughout the entire project. The vibration monitoring equipment had a live feed to the site manager’s mobile phone. This alerted him of any recordings exceeding the recommended exposure limits.
Upon breaking out the party wall to the east of the site, it was identified that the walls were double-skinned and could be dismantled without any interference to the adjoining property. Due to the size of the wall area to be demolished, a Brokk 90 was used. This is a robotic demolition tool attached with a hydraulic hammer to break out the bricks and concrete. The Brokk was craned into the building through an opening cut out by hand for internal operation. Structural calculations dictated the use of temporary propping in order to support structures under operation. The Brokk was then utilised to break out the remaining roof and to demolish the party wall.
A different approach was used for the party wall separation to the north of the site. Firstly, working from scaffold platforms, the reinforced concrete framed façade was dismantled by hand. This continued until the roof level had been reached. Earlier investigations to the roof identified the construction as having reinforced bars running from the front wall to the rear. This allowed the separation of the roof away from the attached Thompson unit and was cut by hand in one metre lines. Lawson Group continued with the floor removal in a retreating method from the Thompson unit to the opposite corner of the unit to be demolished.
Works to remove the concrete framed façade were then resumed with all materials falling into the site. This was completed before mechanical demolition started. Due to the size and tight space constraints within this site, a Brokk was initially used to demolish the north-east section of the building in order to make room for Lawson Group’s 20-tonne excavator. A CAT323 was then used to progressively demolish the remaining structures. A Dust Boss machine was used as a dust suppressant to spray a surfactant across the demolition area.
An unknown basement was discovered below the buildings, all foundations and supporting walls were demolished and removed from site.
Throughout the project, banksmen were positioned to the perimeter of the site and all site personnel were able to communicate through radio communication. High risk works were completed outside of normal working hours and all deliveries were scheduled to avoid busy periods. The site manager was in regular communication with surrounding businesses and Town Centre Management to ensure everyone was kept up to date on proceedings.
All demolition waste was segregated ready for recycling and disposal – 96% of the site waste was recycled. As the producer and transferor of waste, Lawson Group ensured the duty of care was met for waste transported under its waste carriers licence.
The site was left clear and level on time, ready for reconstruction. A formal completion was agreed and the site was handed over to the client ready for the next stage of development.