Traditional underpinning is quite rare in Ireland but this project was perfectly suited to this form of foundation remediation. The property was moving due to escape of water from old clay drains which had washed away the fines of the underlying soils.
Such was the movement in the front corner of the property that lateral displacement warranted a local ‘demolish and rebuild’; movement in the garage warranted a similar approach. Such measures are very rare in subsidence cases as issues are normally addressed during the loss of serviceability stage.
Traditional underpinning simply involves excavating below foundations in a particular sequence to good bearing ground, pouring concrete into the space and dry-packing on completion. As the front corner was considered the most vulnerable, it was agreed that flooding up would be more appropriate. Good ground was found via the local Lucan formation at depths of about one metre.
A combined drain which served the neighbouring properties was just about remote enough away from the foundations to negate the requirement for temporary drainage which made this project so much easier.
Substruck completed the underpinning phase only; a general builder was employed by the insured to complete the enabling and general construction works.