Foundation Heave

Foundation Heave – The Not-So-Hidden Risk of a Plumbing Leak

Ian Mutuli
Updated on
Ian Mutuli

Ian Mutuli

Founder and Managing Editor of Archute. He is also a graduate architect from The University of Nairobi, Kenya.
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What is Foundation Heave?

Foundation heave is cracking and lifting up of the base of your home caused mostly by excessive moisture in the soil beneath which reacts to water and swells under concrete slabs. It is the opposite of subsidence which is the foundation sinking due to poor soil quality.

Other causes of cracks in the foundation can result from severe storms or extreme weather events exerting force on the home’s structure, large tree roots that grow under and up through the foundations, or in rare cases earth tremors that shake the foundations. All of these causes translate into shifts that can send fissures through the concrete foundation. Of these causes, it is excessive water and the soil’s reaction to the wet that is the primary reason for damage to foundations; but where does this excess water come from?

What Causes Water-logged Soil Under Homes?

The main cause of accumulated groundwater is in fact plumbing and drainage leakage from broken or burst pipes. And what causes pipes to break happens to be disasters, rain, storms, extreme changes in weather temperature, tree roots and sometimes just pipes being old.

Older homes with clay pipes tend to have foundational problems more than newer houses using PVC pipes and better materials. And ironically, the foundation heave itself can damage plumbing which in turn causes more water to seep into the soil which can worsen the cracks in concrete floors. It can become a perpetual cycle that should be stopped early before it gets out of hand.

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When addressing the problem of foundation heave firstly you should determine what has caused the damage. If you can rule out storm damage, earth tremors, tree roots or age deterioration, then the most likely culprit is water-logged soil. As previously stated, usually this is an effect of:

  • Plumbing leakage
  •  Underground aquifers
  • Excessive rain
  • Overflow from drainage pipes, irrigation or nearby dams.

In any case, the problem is usually both man-made and natural. Modern construction takes into account possible problems of foundation heave before the house is built. They do this by putting in place drainage systems to alleviate excess water in rain or shine.

They check the ground soil for reactivity to water and compensate for expansion as well as subsidence. This does not always ensure flawless foundations. Therefore, in nearly all cases of this problem of heaving, the main cause of any uplifts of concrete slabs or floors can be traced back to an unexpected failure in plumbing, or leaking pipes.

If the plumbing system that is designed to redirect water during heavy rain overflows or is leaking, then drainage will be minimal around the house and groundwater will accumulate.

If there is a break in the indoor plumbing then water can seep from sewage systems into the earth. With or without the compounding factor of frost and freezing temperatures, the soil will absorb the moisture, expand and lift upwards in a fissure into the base of the home. Foundation heave can be disastrous and cause homeowners much heartache and trouble.

What’s The Solution?

Foundation heave is a two-part problem. First and upmost, homeowners should identify and eliminate the cause and then repair the damage. In the case of foundational heave, caused by plumbing leaks, homeowners need to -

  •  Look for signs of plumbing leaks.
  • Repair the plumbing leak.
  •  Repair the damage to the founding base.
  • Take preventative measures.

Sometimes signs of the damage include doors no longer fitting properly into door jambs, windows not closing and even cracking, bulges in the floor closest to the ground, uplifted slabs of concrete, and at its worst, damage to walls and home structure. Next, a search of the property for any sodden patches of earth can uncover a broken pipe contributing to foundation heave.

Damage Control

There are a number of solutions to foundation heave once the cause has been addressed. The homeowner can enlist a team of plumbing experts, geo-technicians, and construction tradesmen who can work together to:

1.      Test the soil for reactivity to water.

2.      Inject special resin into the earth under foundations to compact and strengthen the soil.

3.      Repair and level the foundation so it is realigned with the house.

4.      Ensure that drainage does not overflow and pool in certain areas.

5.      Ensure that plumbing is built to industry standards.

6.      Ensure that plumbing connections are expandable to take extremes in temperature.

7.      Regularly check the property for leaks in pipes or damage to the foundation.

In Australia, floods and prolonged rain events can bring groundwater levels to record highs and thus naturally increase the chance your plumbing will fail due to soil swelling and fissures appearing in the foundations. Follow the steps above.

As a related point of interest, there was even an earthquake in Newcastle, NSW in 1989, which caused $4 billion in damage to around 38, 000 homes and buildings. It was reported that soft sediments may have intensified the shaking which caused worse damage to foundations and houses.

The importance of the soil beneath cannot be stressed enough for healthy foundations. As we have seen though, softer and reactive soils can be compacted and treated with resin to support foundations. Foundations are perhaps the most important part of a building. But 21st-century plumbing leakage still remains the major cause of foundation heave and structural damage. So, be aware of the tell-tale signs and follow the steps outlined above to stop foundation problems before they even start.  

Ian Mutuli

About the author

Ian Mutuli

Founder and Managing Editor of Archute. He is also a graduate architect from The University of Nairobi, Kenya.
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