Underpinning Adelaide

Underpinning Adelaide, South Australia.

Many houses in Adelaide have stood rock solid for many decades until foundations began to subside as the result of drought which dried out the layers of reactive clay deep in the ground.

Adelaide’s Climate and the Recent Drought

Of the Australian capital cities, Adelaide is the driest, and it has a semi-arid climate influence because of its dryness.

On top of this the recent couple of decades have effectively brought drought to southern Australia. This has affected many properties that had previously been perfectly stable.

So the problem of subsidence has hit Adelaide particularly hard.

Unfortunately many fine houses in various parts of the city have been affected by subsidence. This has been especially the case in the broad residential corridor from Windsor Gardens down to Clapham and west out to Plympton.

The result: cracks in walls and sunken floors, with windows and doors not opening and closing properly.

The Soils in Adelaide

The reason that Adelaide has been so badly affected goes back to pre-history and the geological formation of the area. The relatively flat, and very pleasant coastal area where most of Adelaide now stands is basically formed of sedimentary deposits, forming fairly soft soils.

In addition the soils in many parts of Adelaide contain reactive clays. These clays shrink, often quite significantly, as they lose moisture content. This clay in the soil is the underlying cause of most foundation problems these days.

 Underpinning Adelaide Homes: Why So Many Need It

Since World War II most homes and commercial businesses have been built on concrete slab or concrete strip (perimeter) footings. These footings support the building and provide its stability. The footing itself is supported by the foundation soil below.

Adelaide’s very dry conditions in recent years have reduced the water content of the clay soils under and around concrete foundations. In the protracted periods of hot, dry weather the clay soils have lost large volumes of water and have shrunk. So buildings have lost support, resulting in subsidence of the footings.

Subsidence is generally uneven. As civil engineers know, over many metres concrete footings will bend quite a bit. So walls may develop cracks, inside and/or outside. Windows and doors and can stop working properly, even jamming, if that part of the house subsides.

In some cases gaps appear below skirting boards when the floor has sunk in one place but the wall and skirting board has remained up.

The solution is to raise, re-support and re-level the footings of the house for the long term.

Expanding Resin Injection Solution to Underpinning in Adelaide 

It’s modern: fast, uncomplicated and unobtrusive - like keyhole surgery!  

Structural resins are injected under the house footings. The resins mix together, they expand, compact the ground and lift the house back to level.

 Underpinning Adelaide: Uretek compared to Old-fashioned Concrete Underpinning

Compared with Uretek , the old way involved a lot of hard messy work, jacking-up the house from concrete underpinning. Big blocks of concrete were set in holes excavated under the house footings.  The concrete had to be allowed to cure. Later the house was jacked-up off that concrete.

Concrete underpinning has major draw-backs:

First, it's very hard work and took many days to complete.

Second, it was extremely disruptive and created an enormous mess, covering lawns, landscaping and gardens, plus grit being walked into the house.

Third, concrete underpinning produced major problems for the future of the house. Concrete underpins, unless installed along every part of a building’s footing system, often contributed to future differential movements in the structure.

That happened because concrete underpinning was generally used to re-support a footing down onto a different underground stratum not susceptible to movement. The problem was that whilst the corrected section was then effectively rigid. The adjacent sections that were not underpinned continued to move with ground movement. This created new cracking in the structure - unless articulation joints were sawn right through the walls.

The resin injection technology does not cause this problem. This has been shown clearly by university research and 30 years of practical house re-levelling.

Expanding resin injection is different: it addresses the nature of the foundation soils and any cracks and voids in it. Bearing capacity is improved. Your house is raised and uniformity of bearing strata is maintained.

In relation to concrete underpinning, Australian Standard AS 2870 warns, “Underpinning should generally be avoided where the problem is related to reactive clay,” and  “Deep underpinning should only be considered as a last resort.”

In soft ground conditions, as in many parts of Adelaide, the added weight of concrete or masonry underpinning (at about 2400 kg per cubic metre) can make the situation worse.

With the exceptional stiffness-to-weight ratio of expanded resin material, this does not happen.

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