Top down demolition of a multi storey car park – King Street, Maidstone

Demolition project background

The multi-storey car park in King Street was built in the 1970’s using the “lift-slab” method. The lift slab technique later proved to be prone to failure and despite efforts to reinforce the structure it was declared unsafe and the top down demolition of a multi storey car park was scheduled.

The contract was not only to demolish the multi-storey car park but to also construct a street level car park. DDS proved best value in a competitive tendering process and fulfilled the contract in the role of principal contractor.


Demolition Works:

  • Confirm isolation and termination of services to the structures.
  • Erect Hoarding to secure the site and create a demolition exclusion zone.
  • Install pedestrian and vehicle gates as part of the overall Traffic Management Plan.
  • Erect scaffold / monarflex around the external elevations of the car park.
  • Remove asbestos materials.
  • Remove any other hazardous materials.
  • Soft strip services, fixtures, fittings and non-load bearing structures.
  • Design and install temporary propping.
  • Demolish car park to ground slab level.
  • Remediation works to AMF Bowling party wall.
  • Remove all demolition arisings, rubbish and soft strip materials arising.

Civils Works:

  • Break out isolated areas of slab and back-fill voids with type 6F5 crushed concrete
  • Excavate and install service ducts and new lighting columns
  • Install new power / distribution board.
  • Install new RC kerbs to car park, sub-bases, tarmacadam, wearing course and white lining
  • Plug drainage, install new bypass separator, adjust manholes to new levels, multi-drain and sump units.
  • Excavate and install new RC retaining wall.
  • Excavate and construct new planters.
  • Excavate and install new crossover.
  • Landscaping, crash barriers, chain link fence.

Achievements and Successes

  • The site was in the heart of the town center. The surrounding roads, pathways and shops were all heavily used throughout the duration of the works. Effective dust and vibration suppression was paramount, and such pollutions had to be carefully controlled.
  • The multi-storey car park had practically no room at ground level to use large 360 excavators situated at ground level. DDS employed a top down methodology for the higher levels until suitable space could be created at ground level.
  • Maidstone Borough Council required the project to be completed in time for the Christmas shopping season. DDS had a clearly defined deadline which could not be moved almost completely irrespective of any delays encountered on site.
  • The car park had a party wall with the AMF Bowling center next door which remained fully operational throughout our works. This elevation of the car park had to be carefully razed by hand.
  • The structural failings of the car park imposed strict floor load limits on DDS Demolition. The structure had to be reinforced with temporary propping so that the demolition plant required for the top-down demolition would be held by the floor-slabs.
  • A well-hole, a hole cut through each floor at the same location, was used to clear all waste from the working level to the ground floor. This regular waste clearance prevented the overloading of the floor slabs.
  • Over 98% of the waste arising from the demolition process was recycled, with a very high percentage of this re-used on site for the sub-base to the street level car park.