Concrete Underpinning Vs Resin Injection Underpinning to Fix Subsidence

Cracks in walls near doors or windows can indicate a problem developing with your home’s foundations. Another sign that something’s amiss beneath your house are floors that start to slope.

If the underlying structural issue is subsidence, your foundations are sinking because of unstable soil that’s probably become too dry or too damp.

One of two engineering procedures is typically used by Melbourne underpinning contractors – concrete underpinning or resin injection – to fix the problem by strengthening the base for your foundations.

Concrete Underpinning

Concrete underpinning is the more conventional method to fortify foundations – by extending the depth of the foundation into firmer soil.

It entails digging holes and pouring concrete into them. The concrete is then left to set, creating a new foundation beneath the existing one.

Concrete underpinning is commonly used for smaller jobs. Although a well tried and tested engineering technique, it can be a slow, messy and labour-intensive process. Another potential drawback is that the deeper soil may not be sufficiently solid.

Resin Injection Underpinning

A more contemporary but still proven method of underpinning foundations, resin injection involves drilling small holes into the ground around the foundations and filling them with eco-friendly resin.

The substance expands beneath the foundation and elevates it back into its correct position. The resin also compacts the surrounding soil to prevent expansion or shrinkage. As more resin is injected, it will gradually lift the house above.

Unlike concrete underpinning, resin injection is a fast process requiring little or no excavation.

On the downside, resin injection underpinning may not be cost effective if it turns out there’s a large gap under the ground, which may need a lot of resin to fill it.

Preventing Further Subsidence

Subsidence experts say resin injection holds several advantages over concrete underpinning, including:

  • Speed.
  • Lack of disruption.
  • Versatility.

They point out, though, that for small jobs, concrete underpinning could be the cheaper option.

Both concrete underpinning and resin injections by Melbourne underpinning contractors have been proven to be effective in stabilising the ground underneath a building to prevent further subsidence.

Signs of Structural Damage Caused by Subsidence

Structural damage to your home can occur through subsidence when the foundations begin to sink because the earth beneath them has become unstable.

Subsidence is one of the most serious problems a property can suffer. If the foundation can no longer support the weight of your house, it threatens the structural integrity of the building and can slash its resale value.

Spotting signs of damage due to subsidence during the early stages gives you the opportunity to take measures to halt further structural deterioration and prevent similar problems in the future.

You shouldn’t necessarily assume the worst, though. For instance, surface cracks are far more likely to be the result of natural swelling and shrinkage because of humidity and temperature fluctuations. Freshly-plastered walls and ceilings can also develop small cracks as the plaster dries.

Types of cracks that point towards structural damage include those that are:

  • Near windows or doors.
  • Visible outside and inside.
  • Below the damp-proof course.
  • Where an extension joins the house.
  • In your basement.
  • In exterior brickwork.
  • In a chimney.

Other signs of subsidence-related structural damage include:

  • Bowed walls.
  • Gaps between walls and floors.
  • Nails popping out.
  • Wallpaper wrinkling near the ceiling.
  • Windows and doors sticking (the frames may be warping).
  • Uneven floors.
  • Front porch pulling away.
  • Gaps in the exterior of window and door frames.

Getting an Expert Opinion

Unless you’re a structural engineer, the only way to determine whether subsidence is damaging your home is to consult a specialist in foundation and subsidence inspections.

You’ll find that a good underpinning contractor in Melbourne will carry out a free assessment of your property and advise you on any necessary steps to halt progression of structural damage and/or safeguard against problems further down the road.

How Long Does Underpinning House Foundations Take?

Underpinning a house to strengthen its foundations becomes necessary in the event of subsidence – when unstable soil causes the foundations to sink – or if you want to add extra floors.

Either way, underpinning technologies have advanced rapidly in recent years, and several different methods are now available.

Because of the complexities of the job, it’s difficult to predict exactly how long an underpinning project will take, but on average it works out at around four to six weeks.

However, some underpinning or restumping jobs may take longer, especially if unforeseen snags arise – a particular problem in older houses.

For instance:

  • Utility lines may need to be relocated.
  • HVAC (heating, ventilation and air conditioning) systems may have to be modified.
  • Basement stairs could need extending or rebuilding.

The Underpinning Process

Underpinning begins with digging out the ground around the foundations. This is followed by the actual underpinning process. Three techniques popular among Melbourne underpinning contractors are:

  • Concrete underpinning.
  • Placing reinforcing beams.
  • Resin injection.

Concrete Underpinning

Concrete underpinning is often used for smaller jobs. It involves pouring concrete into excavated cavities. As the concrete sets, it forms a new foundation underneath the existing one. It entails the use of formwork moulds and reinforcing steel wires to ensure the concrete is the right shape and size.

Reinforcement Beams for Underpinning

Reinforcing beams – or piles – are driven into the ground or fitted into drilled holes until they’re anchored in stable soil.

Resin Injection Underpinning

With resin injection underpinning, small holes are drilled into the ground around the foundations and filled with environmentally-friendly resin.

Need a Free Underpinning Evaluation?

An experienced Melbourne underpinning contractor will be able to give you a better idea of how long your underpinning job will take – by carrying out a free inspection of your home.

They can also take care of all the preparatory admin work including getting the necessary permits.