Screw Piles are tubular hollow sections of steel with a helix at the bottom. The screw pile is driven into the ground using an excavator and hydraulic driver attachment. The benefit of a screw pile is that it can be driven through upper levels of soil to better ground where a foundation can be found or re-levelled from. Screw piles can be temporarily installed to re-level a house or permanently installed to found the foundations on better ground at lower depths.
To re-level a house using temporary screw piles the lifting locations are marked out following engineering designs, usually between 1.5m and 2m spacing’s. Excavations are made at the marked locations to expose the base of the foundation and screw piles are driven to the required depth usually less that 2m for temporary screw piling. Once the screws are installed lifting brackets are attached to the foundation and lifting can begin using hydraulic jacks.
Once the foundation has been lifted to the required level, temporary boxing is installed around the screws and cement based grout fill is pumped under the foundation to fill the void created by re-levelling. Once the grout has set the screw piles and brackets can be removed.
If permanent screw piles are being used for re-levelling, screw piles and brackets are left in place.
Screw piles can also be used as a form of deep ground improvement installed under a new foundation.