"Underpinning A 200 Year Old Structure"

 

The key to retrofitting a basement underneath a building is, obviously enough, supporting the existing building.  Even while we excavate away the ground underneath the building we have to ensure that the building above does not shift or settle at all.  To do this we have to ensure that the mass of the building is transferred via suitable foundations to solid ground at all times.

To illustrate this case study we are using photographs from project sucessfully completed for a South County Dublin hotel. The requirements was to extend the hotel at basement level into the garden while preserving the feature granite walls that frame the garden. This type of wall weighs about three tones per linear meter. So keeping them from moving was a complex task.

 

A method we commonly use is called “Underpinning”.  Very simply this involves excavating underneath the existing foundations and extending them downwards.  Naturally we don’t tried to do the entire foundation at the same time rather we do a small section at a time.  The size of these sections depend very much on the site in question but are typical about a meter wide and a meter deep. 

This is the most crucial phase of a basement project and needs to be very carefully performed and monitored.  Once we have painstakingly excavated a section by hand, we can then add steel reinforcing rods around which we pour concrete.  Using this method we can ensure that the extended foundations are far stronger than what was there before. 

While the first section cures we then move off to a different section of the foundations and excavate another section by hand and repeat the process.  In this way the house is slowly extended downwards, while remaining perfectly steady and still.  Once the foundations are secured the excavation can processed at full speed. 

 

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