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What Is House Underpinning?

What Is House Underpinning
What Is House Underpinning
Are you searching for information about house underpinning? If so, don’t hit that back button because that’s what this article is about. We’re going to go over what house underpinning is, why a house might need underpinning, types of house underpinning, and more.

What Is House Underpinning?

House underpinning is a foundation repair procedure used when a house’s foundation can no longer support it because the foundation has weakened for some reason. The problem is usually soil-related. The soil has become unstable, and this has caused the foundation to move and settle into the ground unevenly. This is called “differential settlement.” See the graphic below for an illustration of differential settlement.
differential settlement epp
House underpinning makes the foundation stronger. It extends the foundation down to load-bearing soil that can support it. This not only stops further differential settlement but raises the foundation as well.

When Does A House Need Underpinning?

A house needs underpinning when the original foundation can no longer support the structure. Usually, this is because of differential settlement. 

All houses settle slightly – we’re talking fractions of an inch – after they’re built. This is normal and nothing to worry about so long as the settlement is uniform. That is, as long as the house settles into the soil as one unit. 

Problems develop when a house settles into the ground unevenly, as shown in the graphic above. This is differential settlement, and it can happen to both new and older homes. 

But what causes differential settlement?

Main Causes Of Differential Settlement

Various things cause differential settlement, including:

  • Expansive soil – Soil with a lot of clay is called “expansive” because it expands when it absorbs moisture and shrinks when it dries out. This swelling-shrinking cycle is usually seasonal and creates movement under the foundation, leading to differential settlement.
  • Soil that wasn’t compacted before construction started – Soil needs to be tamped down before you build something on top of it. If this isn’t done correctly, the structure will settle unevenly into the soil after it’s built, causing differential settlement.
  • Natural disasters like earthquakes, floods, tornados, and sinkholes
  • Poor construction – Unfortunately, it happens sometimes.
  • Soil erosion under the foundation – Soil prone to erosion can wash away, leaving voids behind. When the foundation settles into the voids, you get differential settlement.
  • Soil creepSoil creep – also referred to as downhill creep – is when soil at the top of a hill gradually slides down the hill and ends up at the bottom. When soil creep happens around a foundation, it can cause foundation trouble.
  • Large trees – Large trees looking for water can “drink” water from the soil leaving behind voids that the foundation might sink into, leading to differential settlement.
  • Poor drainage around the foundation – Poor drainage and expansive soil can create problems for a foundation.
  • Excavation next door – If your neighbor starts digging a big hole too close to your house’s foundation, it could destabilize the soil under your home, causing differential settlement.

Types of House Underpinning

The two most common house underpinning methods are push piers and helical piers. Here’s how they work:

Push Piers
The push pier installation process is as follows:

  • Steel brackets are attached to the foundation footer. 
  • A hydraulic ram drives the push piers through the brackets until they reach load-bearing soil.
  • Once the piers are in place, a synchronized hydraulic lifting system raises the house.
  • The hydraulic lifting system is removed, and the piers are left in place.
Helical Piers
Helical piers look like giant corkscrews and are used for both new construction projects requiring a deep foundation system and for underpinning existing foundations. The piers transfer the structure’s load to soil that can support the foundation. The helical piers are turned into the ground until they reach the proper depth and torque requirement.
Push piers and helical piers aren’t the only types of house underpinning methods. Other house underpinning methods include drilled concrete piers and slab piers.

Signs A House Might Need Underpinning

Signs a house might need underpinning include, but aren’t limited to:

  • Stair step cracks in brick or masonry – This is a sure sign the foundation has moved.
  • Floor cracks – Cracks limited to one or two tiles probably happened when something fell on the floor. A crack from wall to wall across the room was almost certainly caused by foundation movement.
  • Wall cracks – Horizontal and diagonal cracks are especially problematic. Vertical cracks usually are a sign the house needs underpinning. Most vertical cracks are harmless and caused during the concrete curing process.
  • Ceiling cracks – Some cracks go across the ceiling and down a wall. This is definitely a sign of trouble.
  • Uneven floors You might not notice a slightly uneven floor.
  • Doors and windows that don’t open and shut correctly – If it’s just one door, it might not be a sign of a foundation problem. However, you probably have a foundation issue if multiple doors and windows aren’t opening and shutting correctly.
  • A ceiling or floor separating from the wall – Even slight separations could indicate a foundation issue.
  • Torn or wrinkled wallpaper – The wall behind the wallpaper might be cracked.
  • Moldings that are separating from the ceiling or floor 
  • Leaning chimneys or porches 

If you see any of the above or anything else that strikes you as suspicious, contact an experienced foundation repair contractor or structural engineer immediately. A foundation repair contractor can also give you a repair estimate. 

How Much Does House Underpinning Cost?

The cost of house underpinning depends on various factors, including the type and severity of the damage, the chosen repair solution, and your geographical location. Ease of access to the job site also plays a role. 

If you suspect your house might need underpinning, contact an experienced foundation repair contractor in your area and ask for an inspection and repair estimate. 

Whatever you do, don’t put off getting your foundation repaired. Foundation problems worsen over time; if you wait, you’ll pay more for the repair. Save money by acting early.
how to keep water away from a house foundation

How To Prevent The Need For House Underpinning

Since poor drainage around the foundation is one of the leading causes of foundation trouble, you can do a lot to prevent problems by simply getting groundwater under control. Here are a few ways to do that:

  • Make sure your yard is graded correctly – The yard around your house should slope away from the foundation so that water doesn’t drain toward the foundation.
  • Clean your gutters regularly – Gutters full of leaves and other debris can cause water to flow over the side of the house and soak into the soil around the foundation.
  • Install downspout extensions – Your downspouts should release water no less than four feet away from the foundation.
  • Don’t plant water-hungry vegetation next to your house – When you water them, you’ll add water to the soil around the foundation. This is what you’re trying to avoid.
  • Install a drain tile system – You can’t beat a drain tile system for controlling groundwater. For more information, see, How Does A Drain Tile System Work?

If you believe your house might need underpinning and you’re in our service area in Nebraska, Iowa, Kansas, and Missouri, contact us today for an inspection and repair estimate.


Dave Epp

Dave is the President at Epp Foundation Repair with over 27 years of experience in the industry. Dave has worked on thousands of foundation, basement, concrete, and crawl space repair projects since 1993. Dave is involved in several civic and church organizations and enjoys coaching youth sports, mainly football, golfing, and elk hunting.



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