Underpinning a Failed Foundation

In July, we were approached by Peter at Foundation Solutions Ireland whose client was building a Residential Log Cabin as an extension to an existing cottage. They were experiencing some issues with a previous extension and contacted Peter to see if he could help.

"The problem was an existing extension was sinking slowly causing structural cracks so they asked us for a possible solution with our foundation groundscrews. The site is old shallow bog with 1.2m of bog soil on 1m of normal sandy soil and then in to the harder subsoil where we hit a rock base."

Peter found us through our website and we helped devise the best solution. Groundscrews would not have been suitable as they could not be installed deep enough into the harder ground to ensure no further movement on the property.

Our underpinning solution is ideal for briefs like this as it causes minimal disruption and can often be hand installed which negates the need for an excavator. Subsiding properties are often due to insufficient foundations or shallow footings on ground conditions such as clay and, in this case, bog land.

"We contacted ABC Anchors who were able to supply us the machinery and large helix screw anchors. The support plates reached the required torque at between 2m-3m depth and the extension is now supported fully to prevent any further movement."

Screw piles have many benefits. If you are experiencing problems with a subsiding building where our underpinning solution may be suitable, or you have any other screw pile enquiries, please don't hesitate to get in contact with us.

Underpinning – Conservatory

A conservatory which had been unsuccessfully underpinned using concrete, has now been restored to its original level using 60R helical screw piles.

Initial soil tests indicated that competent ground would be located at approx. 2m depth. However, inspection of the failed foundation and the local presence of trees shed some doubt on this information.

Pile installation was very quick with all equipment hand portable on site.

On this site conventional foundations looked OK but were in fact terminated just above a layer of poor ground.

A two man crew took 1½ days to complete the operation.

Piles were positioned to avoid a number of underground services/utilities.


Using the ABC 400H hand held driver, which has a continuous torque read out, our operators discovered that the competent ground overlay a 2m thick band of soft material. The piles shown were driven to depths of 5-6m before achieving satisfactory installation torques and standard underpinning brackets were then installed and carefully jacked using our 40KN/pile system.

The photos show the ground beam has now lifted from the conventional concrete underpinning and is restored to its original level.

Foundation Repairs

Foundation Repairs – Underpinning

Subsiding properties are becoming more common. This is due to new buildings and extensions being built on insufficient foundations or shallow footings on clay soil. We have developed a system which can stabilise the subsidence and in some cases lift the building back to its original level.

The process involves digging around the outside of the failed foundation to expose the base of the concrete foundation. Pockets are then dug under the foundation at 0.8m-1m ctrs. Where the pockets have been dug, screw piles are installed to torques in excess of 3kNm. Piles need to be installed into stable ground. Jacking plates can then be fitted to the piles and lifted using hydraulic jacks. Once all of the piles are preloaded equally, the process is complete with the building stabilised and in some cases lifted back to original levels. Trenches are then backfilled with soil or type 1 if extra support is required.

Key Features

Can be hand installed for sites with limited access
Minimal disruption to property and surrounding area
Noise and vibration free operation

We have worked with numerous window companies to support and lift subsiding extensions and conservatories.

Access all areas – Underpinning with Helical Piles

Using helical screwpiles to underpin buildings suffering subsidence offers an alternative solution to concreting.

The practice of underpinning buildings with pumped concrete can, in some circumstances, disturb the ground and, in extreme circumstances, make the original problem of subsidence worse.

Using steel screw piles to overcome subsidence is a popular solution, since they can sit in good competent soil at depths of 2m-3m or deeper.

Director of screw pile supplier ABC Anchors Richard Robinson explains: “Subsidence generally occurs in soils that are ideal for screw piling. If the ground is so hard that a screw pile won’t go in, it is unlikely that subsidence will occur. A simple handheld soil probe will determine soil classification data allowing the most economical pile for the job to be designed.

“Where contaminated soils are overlaid with good soil, screw piles can also provide an excellent solution without arisings. In areas sub· ject to flooding, the screw pile will also resist multi-directional loads.”

One of the biggest issues surrounding underpinning projects is that of access. There is often limited room for equipment, and for home owners there is understandable concern if the work must be carried out from within the building. For these jobs, work has been made easier through the introduction of handheld drivers for the installation of screw piles.

Robinson, who has 25 years’ experience of designing handheld drivers coupled with eight years’ experience of manufacturing screw piles, has developed a handheld screwpile driver that uses a hydraulic drive system to overcome installation problems.

“Existing drivers use a heavy motor/gearbox unit at the top of the pile,” he says. “This means that not only do operators have to lift the heavy pile into a near vertical position, but the drive and torque reaction arm has to be lifted 2m in the air as well. This procedure is potentially hazardous and usually taxes the strength of operators to the limit.

“As the pile travels further into the ground, and especially when an extension has been added, the increasing torque reaction tends to force the head of the pile towards the operators. This is a further hazard and exacerbates the problem of using foot controls in muddy, slippery and uneven sites.”

Electric handheld 110 volt mains or lower voltage battery-powered units can provide lighter and more convenient solutions, Robinson says, but they can lack the oomph needed to construct deep foundations.

Robinson’s new ABC 400H Hydraulic Driver uses a standard 301 140Bar power pack with a hydraulic drive system. Having a separate hydraulic power pack with long hoses allows the operator to still work in confined spaces.

“While the 400H Hydraulic Driver still isn’t super light, it’s much easier to operate,” says Robinson. The handheld controls permit logical operation and offer immediate control, making for safer and more accurate installation rather than chasing foot controls in muddy trenches, which can be dangerous.

The new driver permits the installation of 3m or even longer piles in one piece without the use of extensions, saving money and time.

Robinson adds: “Because the handheld hydraulic control is so sensitive too, piles can be installed within +/-1.5mm of correct depth. This makes the formation of precision foundations much easier.”