underpinningPiling and underpinning are techniques used in the construction trade to repair problems caused by ground heave or subsidence and to mitigate against the risk of future movement within a building plot.

Using columns of metal, concrete or other materials, the weight of a building is transferred in a planned direction to stronger, more compacted soil underneath the surface soil.  Rafts and pads of concrete may also be deployed to form a reinforced, stable area to build on.

The main benefit of piling is that it is a relatively quick and cheap way to stabilise the ground beneath a building and meet structural requirements and building standards.

When Is Piling Indicated?

displacementPiling

  • Piling is also useful as a protective measure to preserve pipes when building over pre-existing services such as sewers, water mains, gas lines etc.
  • Piling will also be required when extending premises which have previously been built on a piling platform.  This ensures that there is no differential movement between the old and new building.  If the original building required piling as part of the construction, then any new work on the same plot would likely require piling regardless.
  • If there is a risk of tree roots causing damage to the proposed plot, or if subsidence has already proven to be a factor, then piling will also be a likely suggestion as a preventative measure.

pileAndBeamBefore Piling Can Begin

  • We visit your site to inspect it and discuss your project needs
  • We take a selection of soil samples from across your site to use for strategic analysis.  The results of this allow us to determine the optimal piling type for your building.
  • We create a piling design.  Our engineers calculate the required materials and structures to safely bear the building.  We then compile a list of specifications to go with the designs and submit the report for building control/authority approval.

What Types Of Underpinning And Piling Can You Carry Out?

We have expertise in many forms of remedial piling and underpinning such as:

If your property has suffered subsidence or ground heave, underpinning may be required to stabilise the ground under the building.  Underpinning requires us to remove soil in blocks from underneath alternative sections along the foundations under the walls of your premises.  Once these have been inspected, the excavated areas are filled with concrete.  The process is repeated along the foundations until the effected area is totally supported.  The result is a much more stable support for the foundations where the soil had failed.
Essentially, infilling spaces which have opened up below the concrete base ‘slab’ and destabilised it.  Holes are bored through the existing concrete and grout is pumped through these holes to displace air-spaces and replace them with a hard substance.
Using the grout and pile method, grout is pumped through holes made in the existing concrete slab.  Piles are driven down through holes, the slab and weakened substrate to harder soil.  This offers further structural support to the slab and is a more thorough process than grouting alone.
If your entire premises have been effected by ground movement, this method might be the best choice.  It necessitates the removal of floors as small supportive piles are inserted.  Brickwork is removed at alternating points and reinforcements are placed in situe until the work has passed inspection.  At this point, the cavities left by removed brickwork are filled with concrete.
Knuckle piling is similar to raft piling, but is only used on parts affected by subsidence or heave rather than the whole building.  Once the ‘mini’ piles are inserted in key areas, bricks are removed and the site is inspected by building control.  Reinforcing cages are placed in the excavated / removed areas and are then concreted.  This technique can be especially useful in areas with limited access.
Twin Piling is a simple procedure with minimal disturbance to the site and premises.  Pairs of ‘pile and prop’ are delivered through channels drilled out to the area beneath the concrete or brickwork foundations of the building at specified intervals.  This technique is popular where a discrete approach is desirable as little evidence of the work remains afterwards.
Angle piles are mini-piles which are inserted obliquely through the foundations of the building.  In combination with the existing foundations, these doubly braced piles help to form a more stable support for the walls above.

The pile and beam technique involves sinking small piles either side of the wall which needs the support.  A portion of the brickwork is removed from the wall at foundation level and a cage installed through the gap to rest on the top of the piles, forming a bridged section.  After inspection, the cage is filled with concrete to form the solid supportive structure.

The cantilevered version of this process is performed entirely from the outside of the property to avoid internal disruption and where there is insufficient space to work within the structure.

There are two main types of Piling:

Where shafts are bored out of the earth and the soil replaced with piles that fit into place as tightly as possible.

Typical Types Of Replacement Piling Include:

  • CFA – Continuous Flight Auger
  • Open-Hol Auger-Piles
  • Rotary Piles (Large Diameter)

Replacement Piling Pros

  • Quieter and causes little vibration.
  • Effective in soils which are non-cohesive or water retaining.

Replacement Piling Cons

  • Soil removed from the ground needs to be disposed of, usually off-site.  This can be costly if debris is contaminated.

Where pre-cast piles are driven into the ground using a large hammer or thumper style device to literally displace the soil around the pile.

Typical Types Of Displacement Piling Include:

  • Concrete piles
  • Thick steel tubes
  • Thin bottom piles
  • Wooden piles
  • Screw piles
  • Helical displacement piles

Displacement Piling Pros

  • No soil or debris to dispose of.
  • Little disruption to the pile area.

Displacement Piling Cons

  • Noise and vibrations caused by the driving process can be quite obtrusive.
  • Some clay layers or obstructions can prevent penetration of the pile.

 

If You Have A Piling Project In Mind Contact LEBC

call us on: 01676 545 051

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