What is an Active Zone? (What You Should Know for Foundation Repair)

You’re seeing some cosmetic issues with your home, whether it’s your floors are sloping as though you can slide down a dry waterslide (would not recommend), cracks in your drywall, windows are difficult to open and your fireplace leans away from your home as if it’s stealing the warmth for itself. What is causing these things to happen?

Likely it’s the active zone in the soils under your home shifting around, causing undue foundation settlement or heaving to an area of your home. 

But what the heck is an active zone? Why is it doing this to your home?

Dalinghaus Construction has inspected over 10,000 homes, effectively repairing over 2,000 homes in Southern California, Arizona, and Nevada by understanding how the active zone works. We’ve installed thousands of push piers and helical piers past this zone to ensure stability to your home, ensuring it doesn’t deal with settlement issues for years to come. 

What is an active zone?

It isn’t an area where the neighborhood gets together for exercise and other physical activities. That would be a wonderful community bonding experience, but your home has to deal with a different kind of active zone.

Pertaining to foundation repair, an active one is an area of expansive soil usually between the surface of the soil and six feet below grade in the presence of moisture. This is where the soil is most prone to expansion and contraction due to the moisture content, which happens naturally. 

Anything below this usually isn’t affected by moisture changes. Think of it like stacking a bunch of towels on top of each other on your bed. Pouring water on the top towel likely won’t soak onto the bed. 

Dalinghaus Construction does not endorse you doing this experiment for the purposes of this analogy. 

An active zone can also be affected by seismic activity, which is less common, but can be the cause of movement. Moisture will have more of an effect compared to seismic activity.

Your home is susceptible to foundation settlement or heaving since it will be in the active zone.

  • Foundation settlement – An area of your home is sinking due to expansive soils drying up and contracting due to a lack of moisture.
  • Foundation heave – An area of your home is being pushed up due to expansive soils absorbing moisture. 

The natural temperature resulting from the weather can affect the active zone. If it’s dry outside and hot, the soil will contract and condense together. If the weather is wet and cold, the soil is likely to expand. And when moisture shifts, the soil can also shift. 

An active zone can also affect lateral movement

If your home is on a slope, moisture can still be involved. However, gravity doing its job of keeping everything grounded can sometimes contribute to a home sliding down a hill. Not literally. It will slowly move, but it isn’t a terrifying roller coaster ride without secured seats. A slope can cause your home to move laterally at the pace of a sloth laughing while working in the DMV (Zootopia reference). 

This is referred to as slope creep, or “the slow, gradual downward displacement of soil, rock, and organic material.”

Slide down into our article What the Heck is Slope Creep? (How to Mitigate Lateral Movement) to understand more about slope creep.

What determines an active zone?

It depends on how deep surface moisture can get. So when we say “usually six feet,” an active zone isn’t always at a depth of six feet. That’s more the average of where the end of an active zone would be. If there’s more expansive clay present, the deeper that water will get.

Let’s go back to the towel analogy, but instead of using regular bath towels, we’ll go with paper towels. If you were to stack paper towels on top of each other on your bed, pouring the same amount of water on them would likely reach your bed.

Again, Dalinghaus Construction does not endorse you wetting your bed for the purposes of this analogy.

Bad analogies aside, the point is different soils soak in moisture differently. It isn’t necessarily important to know what type of soil you have but to know if it’s expansive. The presence of clay will play a major factor. 

Spoiler alert: In most cases, there will be clay present. 

A list of expansive soils includes:

  • Smectite
  • Bentonite
  • Montmorillonite
  • Beidellite
  • Vermiculite
  • Attapulgite
  • Nontronite
  • Chlorite
  • Pedialyte
    • Not to be confused by the oral electrolyte solution after a hard night of pouring liquor into your towels after an evening of partying and a bad analogy.   

Expand your knowledge by reading our article What is Expansive Soil? For a better understanding of these soils and how they work.

Are shallower foundations more affected by active zones?

It comes down to whether the foundation is past the active zone. If an active zone is sitting at six feet, a two or four-foot footing will be affected the same since they are both in that active zone.

Say you have a seven-foot footing that is deeper than the active zone, then it can withstand movement than its shallower contemporaries. 

Active zones are still able to move even with proper soil compaction

Proper compaction mitigates the problem and decreases the severity of the movement in an active zone, but it doesn’t eliminate the soil shifting 100%. 

Don’t get the wrong idea: you want a home with proper soil compaction. It does help to greatly reduce the amount of settlement or heave your home has to endure.

An active zone can affect your home

Again, your home will experience foundation settlement and heaving. How will you know? Because you will see signs and symptoms that will affect the interior and exterior of your home. You’ll see symptoms such as:

  • Sticking Doors and Windows
  • Cracks in windows and doorframes
  • Ceiling Cracks
  • Water Leaks
  • Sloping floors
  • Drywall Cracks
  • Stucco Cracks
  • Gaps between windows, doors, and walls
  • Floor Cracking
  • Leaning Chimney/fireplace
  • Slope Creep
  • Footing cracks

For foundation settlement or heave, it will never be one of these signs in an isolated circumstance. When you see more than one of these signs in an area of your home, you may have an issue with your foundation. It wouldn’t hurt you to have someone take a look. 

You might not see these signs and symptoms immediately. It could take years or even decades before you notice anything.

While an active zone does move, it’s not like a cheetah going from 0-60 in 3.4 seconds (fun fact). The pace is like that of a snail in a race. You’ll see some movement, even though it feels like it will be forever until the race ends. 

Read The Ultimate Guide to Signs and Symptoms of a Home in Need of Foundation Repair for a more in-depth understanding of how foundation issues affect your home. 

If you need an underpinning, make sure the proposal you receive will have a solution that reaches past the active zone

There are types of concrete underpinnings that are shallow and don’t make it to the active zone. And sometimes the piers will make the foundation settlement worse. Think of it like a sinking ship with the added weight of the anchor. It will sink faster.

There are also concrete piers some companies use that are driven into the ground. Due to the amount of skin friction and resistance these types of piers have to deal with, they don’t make it past the active zone.

Make sure if you have a proposal, the solution should reach past the active zone. 

Dalinghaus Construction uses galvanized steel helical piers and push piers. 

Helical piers have helices attached to them to essentially be screwed into the grown until it reaches competent soil. 

Push piers use the weight of the home to be hydraulically driven into bedrock. 

Both of these solutions reach past the active zone. 

The point of underpinning is to get to the soils underneath the active zone. That way your home won’t be affected by any movement.

The point of any reliable underpinning is to stabilize your home.  

You know more about active zones. If there’s damage to your foundation, get repairs to help your home.

You’ve learned more about active zones and how they affect your home. If your home is experiencing foundation issues, what’s important is to have someone take a look. As the active zone continues to have soils shift, the foundation issues won’t get better. 

Be sure to receive evaluations from multiple foundation repair contractors. That way you can compare methods of repair, pricing, and see if they’re actively getting past that active zone for the stability of your home and peace of mind.

You can schedule a free evaluation with Dalinghaus Construction to see how/if the active zone around your home has caused problems.

Before scheduling a foundation evaluation with any company, you need to read Should You Get Multiple Foundation Repair Bids? (How You Benefit) to understand how you benefit from looking at multiple companies.

Check out What Alternatives Are There to Caissons for Foundation Repair? to figure out what methods of foundation repair work best for you.

For any questions, call Dalinghaus Construction at (877)360-9277, or click the button below to schedule your free foundation evaluation today!


Brian Dalinghaus

Brian is one of the Co-Founders of Dalinghaus Construction. He has been in the foundation repair industry since 2005. During his career, he has been associated with helping over 4,000 homes and structures throughout California and Arizona.

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