Cut & Carve Demolition – Premier House

Complex cut and carve demolition project that required a number of different propping solutions and temporary works. The project was to remove a part of the Premier House structure in Manchester before redevelopment.

The building was located in the city centre of Manchester and was close to the river, Deansgate road and the Victoria Bridge which is a grade II listed structure.

Contractor: PP O’Connor

Client: Property Alliance Group

Project Overview

The whole structure pictured is to be renovated in time, but this case study focuses on the work in the north section (red and orange on the map below) which were completely demolished as part of these works. 

The red and orange area had a 2 to 3-storey basement carpark. Demolition in these areas were the main challenges of the demolition design. 

An existing basement retaining wall supported Deansgate and Victoria Bridge Street and was close to Victoria Bridge.  During the works part of both roads and bridge were still in use, with the hoarding line removing one lane of traffic from each.

Temporary Works Overview

Andun were involved in the temporary works design at the tender stage with PP O’Connor, sitting in on the precontract meetings and delivering the detailed design once they were awarded the contract. 

Key items of temporary works are listed below:

  • Propping and justification of cut and carve demolition of retained structure
  • Propping for small plant (8 tonnes) on the upper levels
  • Backpropping for larger plant (90tonne) on lower levels
  • Basement retaining wall propping to facilitate substructure removal
  • Demolition cut line propping
  • Vibration assessment on underground culvert
  • Movement monitoring and assessment on surrounding structure

Project Challenges and Constraints

One of the challenges was to support Deansgate road during the demolition whilst also permitting the proposed demolition works and leaving open lanes and up to a 90 tonne excavator operating to facilitate the demolition.

Andun worked with the project team to develop a more effective demolition scope that included leaving a bay of structure in that was braced with propping to provide this support. The solution was to use temporary works in combination with the existing structure as shown below.

Retaining wall support photos

The photo below shows some archive photos of the structure being built in the 1970’s

It could be seen from these photos that there was minimal temporary works to support the wall due to the large buttress wall that supported Deansgate Road.

Unfortunately, investigations were unable to gather enough information on the buttress wall structure to remove the requirement of temporary works completely. This is because there was the possibility that the wall had been changed, was in poor condition or the sections of buttress had been removed since the photo was taken.

However, the site investigation allowed for a lighter design than if there had been no existing wall at all. Early on, this investment in site investigation paid dividends, allowing for a saving of time and money on site.

Site Monitoring

Due to the complexity of the project, four different types of monitoring were set up. Assessments and calculations were carried out by Andun and it was found that all movement and vibration remained within the allowable tolerance thus proving the success of the recommended mitigation measures used on site. The following areas were monitored:

  1. Deansgate elevation Movement Monitoring  
  2. Victoria Bridge monitoring
  3. River Wall Monitoring
  4. Services vibration monitoring

Project Impact

The temporary works solutions employed on this project used as much of the existing structure as possible which reduced the amount of propping imported onto site and cut down on installation time.

 This follows our mantra of ‘No temporary works is the best temporary works’.