Residential Property in Dublin

We were asked to underpin an existing extension that was displaying signs of subsidence.  Trial pits had been excavated and they indicated that the foundations were founded on a material with low bearing capacity. 

Our brief was to transmit the load of the extension onto more competent strata by the use of mini piles.

The client had a desire not to disturb his paths and garden and wished the works to be carried out from the inside only.

Our access to the rear of the property was via an 800mm wide gate, this tight access was easily overcome by our T750 drop hammer rig.

Taking these parameters in consideration we decided that our “Internal Piled Raft” solution would best suit the site conditions.  The internal floors were removed to a depth of 500mm below finished floor level to facilitate the installation of a new raft floor slab supported by 150mm dia mini piles.  Pockets were broken out in the masonry and the raft slab extended into these pockets via reinforced concrete needle beams.  The needle beams gave support to the external walls and transferred their load onto the mini piles.

We installed 18No. 150mm dia mini piles to a depth of 7.5m constructed 13 No. reinforced concrete needles and cast a raft slab 300mm deep over a 25m2 area.  These works were completed in 7 working days.

Vibration monitoring was carried out for the duration of the works and vibration was kept to a limit lower than that required for protected structures.

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