Underpinning Elwood

Underpinning Elwood, Melbourne, Victoria.

Information about Underpinning in Elwood the causes of house subsidence in Elwood and available remedies

Many houses in Elwood have been affected by climatic and soil conditions causing the need for foundation/footing remediation in the form of raising and re-levelling.

For many decades houses in Elwood were well supported, but then many foundations began to subside as the result of drought which dried out the reactve clay in the ground.

How the Drought has Affected Underpinning in Elwood

Subsidence can be caused by many things, but the recent 18 or more years of drought in Southern Australia have affected many buildings that were previously quite stable.

The problem of subsidence has hit Elwood particularly hard. A beautiful, prestige suburb on Port Phillip Bay just South-East of the Melbourne CBD, Elwood has many of Melbourne’s finest houses.

Unfortunately many of them have been affected by subsidence. The result: cracks in walls and sunken floors, with windows and doors not opening and closing properly.

The Problem Lies in the Geology of Elwood: Reative Clay Soil.

The reason that Elwood has been so badly affected goes back to the birth of the suburb. The area had been a forest of mangroves where a major creek flowed into Port Phillip Bay.

Then in 1910 the area began to be reclaimed from the Bay, so that homes could be built. That creek was turned into The Elster Canal, and it’s now surrounded by one of Australia’s finest suburbs with many, many lovely green tree-lined streets like Glen Huntly Road, Ruskin Street and Beach Avenue, to name just a few.

The area's soil characteristics result in a significant amount of foundation repair for homes and commercial businesses. As in many other parts of Melbourne, Elwood’s soils contain many clays. And reactive clay soil, Melbourne. is the culprit behind foundation problems.

Why Many Elwood Homes Require Underpinning

Especially since the Second World War homes and commercial businesses have been built on concrete slab or concrete strip (perimeter) footings. These footings support the building giving it stability. In turn, the foundation soil supports the footing.

The problems began with changes in the water content of the clay soils underneath the houses in Elwood. During the protracted periods of hot, dry weather the clay soils lost large volumes of water, so they contracted. Even the brief periods of heavy rain were insufficient to stem this trend that had been getting progressively worse over the best part of two decades. So this shrinkage lead to buildings losing support and subsiding.

Subsidence is usually uneven. Along the length of a house, concrete footings can bend. This often causes walls to develop cracks, sometimes both inside and out. Doors and windows may become very hard to open and close, if that part of the house becomes “out-of-square”.

Gaps sometimes appear below skirting boards because the floor has sunk in one place while the wall and skirting board stays up.

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

One Good Underpinning Solution in Elwood is Expanding Resin Injection

It’s modern, advanced technology that’s fast and uncomplicated, very neat and unobtrusive - often compared with keyhole surgery!  

Expanding structural resins are simply injected beneath the footings of the house. The resins mix together to expand and lift the house footings back to level.

The old, traditional way involved a lot of hard messy work, jacking-up the house from concrete underpinning. Huge blocks of concrete were poured in holes excavated under the house footings.  The concrete had to be allowed to set. After that the house was jacked-up off those blocks.

Three major draw-backs of concrete underpinning:

First, this was very hard work and took many days to complete.

Second, it’s extremely disruptive and creates an enormous mess, covering lawns, landscaping and gardens, not to mention grit being walked into the house

Third, concrete underpinning can produce major problems in the future of the house. That is because concrete or masonry 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 is generally used to re-support a footing down onto a different underground stratum not susceptible to movement. The problem is that whilst the corrected section is then effectively rigid, the adjacent sections that have not been underpinned will continue to move with future ground movement. This can create new cracking in the structure - unless articulation joints are sawn right through the walls.

Expanding resin injection technology does not cause this problem. This has been shown clearly by university research and nearly 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 therein, improving bearing capacity, raising and restoring and maintaining a uniformity of bearing strata.

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 Elwood and many other parts of Melbourne, the added weight of concrete or masonry underpinning (at about 2400 kg per cubic metre) can make the situation worse, not correct it!

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

Compared with concrete underpinning, expanding resin injection is like keyhole surgery!

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