McAlpine take on complex engineering for hotel job

The firm will add two layers of basement to The Westbury Mayfair in London.

McAlpine’s in-house team for the scheme include: 

• The Special Projects team. 
• Geospatial Engineering team. 
• Design Group team. 

Inside the job

The revamp of the seven-storey structure will involve: 

• Removing the rear of the concrete frame building. 
• Digging down two further levels. 
• Extending both out to the site boundary and underneath the existing structure.

After these works, a full-height steel frame extension will be installed. 

Building temporary foundations

To hold the weight of the building during excavation, temporary foundations were put in place for each existing concrete column. 

This solution was developed by the Design Group. 

In the plan:

• Four new piles were drilled 26m into the ground through each of the existing foundations. 
• A steel frame on top took the weight of the building off each column. 
• The weight was then transferred to the temporary foundations using hydraulic jacks. 

With the weight supported, the team then started to remove the old foundations and excavate. 

On completion

When the basement section is complete, permanent steel columns will be installed to extend the existing columns down to the pile caps at the bottom of the basement. 

The weight of the building will then be transferred to the new foundations, with the temporary ones removed. 

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