Foundation Repairs

When it comes to foundations there is:
The three big questions
  • Do I have a problem
  • How big is the problem
  • How much is it going to cost to fix

No matter where in the world you live  you are going to run into foundation problems.

The following info-advertisement  is just as relevant in Australia or NZ  as it is in the USA for home owners, strata managers,buyers, sellers investors in property.

What Buyers Need To Know About Foundation Problems and Repairs

Common reasons for foundation problems

Matric Suction

Is the pressure dry soil exerts on the surrounding soils to equalize the moisture content in the overall whole block of soil. The forces can be considerable and the subsidence significant. it is calculated through steady state seepage analysis.

Trees, ponding water, water ingress around footings and reactive clay soils will precipitate load bearing soil movement.

The quality of your footings will determine if the soil movement is going to fracture your foundation.

Types of Foundation Repairs

  • Foundation Underpinning
  • Helical Piers
  • Helical Pile Applications

The purpose of a helical pier is to transfer the load of the structure through the unsuitable soil to a stronger, more suitable soil deeper in the earth. Helical piers are a deep foundation solution. Helical pier applications operate equally well in tension and compression

Permanent new structural foundations under continuous foundation grade beams or column bases, compression and/or tension loads. Typical ultimate capacities for single piles can range from 30 tons  to 100 tons . In  groups, column design loads of 1,000 tons application would be for new single and multiple story buildings, including high-rise structures, bridges.

Permanent battered piles to take lateral loads including wind and seismic. Lateral loads are taken as axial compression and/or tension loads. Examples of this application would be those listed immediately above but also including sound walls, water towers, communications towers, bill boards, etc.

Permanent new structural foundations under new concrete slabs. Permanent retrofit foundations in existing structures and additions loads are being added to the structure. An example would be where a new mezzanine level is being added inside a building or where new, larger and heavier machines are being installed in a factory. Permanent retrofit structural foundations under existing concrete.

Permanent retrofit foundations for seismic upgrade purposes.

Permanent new foundations under heavy artwork/signs.. Permanent underpinning of any settled or heaved existing foundations, heavily or lightly loaded.  Steel brackets are used to transfer existing loads from the structure to the new helical screw piles.

  • Helical Tension Anchor Applications:
  1. Tiebacks for permanent retaining walls constructed of any materials such as cast-in-place concrete, shotcrete, gunite, soldier beams railroad ties, etc.
  2. Permanent tension hold down for wind loads
  3. Tiebacks for permanent or temporary shoring
  4. Where lateral load resistance is required. All locations where grouted tiebacks are specified and the anchor zone is not into solid  rock.
  5. Their advantage is that their capacity is known and can be verified where as resistance and foundation piles are just calculated and usually not tested as it is uneconomical.
  • Resistance Piers

These are piers used to resist movement, vertically or horizontally. They can be of metal. wood or concrete and can be used to support directly off a solid bed or to provide resistance through frictional force. The piers appear to float in the soil.

  • Foundation Piles

These are piers which support the foundations of a structure. They may be fixed in place before the foundations are placed of maybe poured as an integral part of  the foundations. Common practice for a new house on a cut and fill site is for 300mm diameter piers to be drilled every 1.8m along the length of the footing to a depth of soil showing the same bearing capacity as the deepest cut area of the site, so that all footing will have the same bearing capacity due to the uniformity of soil at the bottom of each pier. This is assuming soil layers are horizontal.

The use of screw piles are proving more popular these days then the bored concrete pile as they are more efficient, deliver better results and are less expensive.

There is no soil spoil to clean up and dispose of, no concrete to source or pump required, smaller equipment can reach greater depth for better soil quality etc. They can be easily modified to accommodate lateral loads, reactive soils and top of pile supports to superstructure.

This video shows a proprietary system for adding lateral strength to helical anchors in poor soils and a range of applications for screw piles and how we use them.

 

Blade Pile being screwed in whilst torque is monitored. Going for rock here as supporting sand has a water table of 1 meter here at Kogarah Bay.