What is Slab Heave

What is slab heave and how does it affect houses?

This is our video on slab heave.

G’day. I’m Matt Cornell from Cornell Engineers.

Today I’m answering a question about slab heave.

Before a house is built on a site soil moisture conditions are fairly uniform across the site.

That changes when a house is built.

The uniform soil moisture conditions are interrupted by the house.

Slab heave occurs in clay soils when the soil moisture conditions under the house are no longer uniform.

When the soil around the outside of the house becomes wet the clay soils absorb moisture and expand.

The expansive forces are large enough to lift a house.

Under the house stays relatively dry.

There is a transition zone between the wet and dry soils as soil moisture transfers sideways.

When the soil around the outside of the house becomes dry the clay soils release moisture and shrink.

The ground surface moves down and the soil under the house is relatively wetter compared to the dry
soils around the outside of the house.

Again there’s the transition zone between dry soils and wetter soils as moisture transitions from under the house towards the dry zone.

Soil moisture conditions aren’t only affected by changing seasons.

Other sources of soil moisture changes are garden irrigation, broken pipes, poor drainage and tree roots.

This has been Matt Cornell from Cornell Engineers talking about slab heave.

Don’t forget to check out our website for more information and to follow us on Facebook.

Just a reminder:

  • Not everyone who thinks they have slab heave does.
  • Not everyone who thinks they have other problems does.
  • Only use experienced structural engineers and geotechnicians to diagnose and fix house movement.

Call Cornell Engineers for more information about slab heave and how to fix it.

3 thoughts on “What is Slab Heave”

  1. Hi Matt,

    Your new video on slab heave is well appreciated. You mentioned abt tree roots as one of the contributing factor to slab heave. As a guide, what is the safe distance for any tree to be oplanted near the house? Example, Castle Wallan. Thank you.

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