Slab heave crack

How to Fix Slab Heave

Slab heave can be fixed. The cracks in your house that open and close can be stabilised. Cornell Engineers has the experience and knowledge to help you fix slab heave.

What is Slab Heave

Read “What is Slab Heave” and watch our video on Slab Heave.

Some signs of slab heave are:

  • Diagonal or stepping cracks in brick and blockwork walls.
  • Cracks coming from the corners of windows and doors.
  • Doors and windows stick and become difficult to open and close.
  • Cracks, gaps or compression of cornices.
  • Gaps under walls.
  • Visible uneveness in floors.
  • Rarely, cracks in floor tiles.

Diagonal crack in a rendered brick wall

Do This First

If you are a homeowner and your house is starting to move and crack, do this first:

  • Start a Crack Diary.
  • Find water sources that are entering the ground around your house and eliminate them.
    • Fix leaking pipes. Get a plumber to help find and repair these pipes.
    • Repair dripping taps. Replace the tap washer or relocate the tap into your yard.
    • Fix broken pipes under your house. See a plumber.
    • NEVER plant trees near your house. Consider removing any really large trees that are near your house (seek help from a structural engineer and/or arborist).
    • Fill in dog holes next to the footings with tamped, moist clay sourced from elsewhere on the block.
    • Capture condensate from air-conditioners and hot water systems and divert it away from your house.

Do these things before you talk to your builder. Do them before you lodge a claim with your insurance company. Do them before you start paying for engineers and expensive chemicals. Do them before you fix ANY damage.

What’s Next

The problems associated with slab heave can often be overcome by one of these solutions:

  • Improve the tolerance of the building to uneven movement. This solution includes articulation gaps and joints and wall strengthening but is only appropriate if the slab doesn’t feel uneven.
  • Remove the cause of the uneven movement. Identify sources of soil moisture and eliminate them or isolate the building from them.
  • Isolate the building from uneven movement. This method includes jacking and underpinning so that the house is supported clear of the ground movement. Not all houses can be fixed this way.
  • Demolition and reconstruction of the house using one or more of the above techniques and/or a stiffer/stronger footing system.

Do it Right

I’m sad to say – unless slab heave damage is repaired correctly, it will come back again, and again, and again. Concrete slab repairs have to be done correctly.

Some builders think that houses with slab heave damage can’t be repaired. Houses with slab heave can be stabilised!

Cornell Engineers have engineered successful repair and rectification projects many times. Matt Cornell has never had to recommend demolition of a whole house because of slab heave.

Let me say that again: In twenty-eight years of full-time practice as a structural engineer, Matt Cornell has never ordered the demolition of a house because of concrete slab heave.

Cornell Engineers can Fix Slab Heave

If your house has moved and cracked because of uneven soil moisture conditions, I can diagnose this problem and help you fix it. I can help you fix your concrete slab heave, reduce cracking and reduce ongoing movement.

In time you will be able to fix the cracks and enjoy your house.

37 thoughts on “How to Fix Slab Heave”

  1. Hi Matt, the majority of builders seem to be using Waffle Pod slabs nowadays as opposed to Raft slabs.

    Our current house is on a raft slab on class H soil and as we are vaguely considering a new house in our local area, I am loathe to get one built with a waffle pod. I find it somewhat disturbing having chunks of polystyrene under my slab rather than nice firm sand, as in a raft slab.

    Anyway, can you offer any perspective on the two slab styles? Which would you use for your own house?

  2. We have heaving and sinking happening at our house. We are on a perimeter foundation with peer pads. The peer pads are what are sinking and heaving. So far the perimeter foundation isn’t moving. We’ve had Ram Jack, Terra Ferma, and a soils engineer out with not a word of advice. HELP!!!! Cracked walls, doors that wont open or close, gaps in between the ceiling and walls and floors and trim. We need an engineer to help with creating something stable for the house to sit on, in its center.

  3. Hi,
    Just wondering if a slab can heave in the middle from the front of the house dipping. I have a thin rectangle slab that is heaving upward around 40-50mm in the middle based on surveys which seems to be splitting the house in half. The front corner has dipped on one side close to the same amount.
    We’ve checked the pipes which run parallel and perpendicular to the cracking under the slab and only found a root in a joint in the kitchen on the other end of the house from the damage. Static fill tests show water leaving the system but the builder says this has to do with the drains in the wet areas. We can’t find any significant cracks in the pipes but all the joints have lots of burrs.
    The builder is saying it is caused by the surrounding pavers not having sufficient falls but there is no damage at the back of the house and rain barely gets down the side most times and the ground under the pavers isn’t excessively wet.
    The ground under the slab on the side of the house the laundry and kitchen are on is soaked, highly reactive clay though the area under the highest point in the house on the other side seems dry. Could water leak from the dodgey kitchen joint and pool in the middle without causing damage in the kitchen? Could water from outside the slab cause something like this?
    There is also a 500mm deep sand trench directly under the footing on the dry side which I don’t think should be there, especially on highly reactive clay. Just wondering what you think – I’m also worried it’s getting to a point if no repair.

  4. Hi Maggie and Rochelle. I’ve been following with interest the conversation you’ve been having regarding your problems with slab heave. Thank you also to Jason for contributing. Maggie you are right – it is a very stressful time. Solving slab heave is a slow process. Rochelle, try to stay positive. Staying informed and asking lots of questions will definitely help you stay in control. The QBCC is very good at solving slab heave issues and the panel engineers are all very experienced. If you’d like to have a chat about your progress, my details are on the website.

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