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How to Fix a Sinking Foundation

Read Time: 8 minutes

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One of the more serious problems with foundations, but an all too common one, is sinking or settling. A small amount of settling is natural and will not cause any major issues, but if the soil under a home has settled significantly, or worse yet, is not strong enough to support the house, then steps must be taken to prevent damage. In this article, we’ll go over some of the causes, signs, and repair options for sinking foundations in the Charlotte area.

First of all, what causes a home to sink? The short answer is bad soil, though it’s a little more complex than that. The type of soil under a home plays a significant role in determining how stable a structure will be.

Clay soils, for instance, expand and contract with changes in moisture levels. When there is a lot of rain, clay soils expand, which can push against the foundation walls. When there is a prolonged dry period, such as a drought, clay will compact and actually start cracking. These cracks create instability in the soil and space for foundation walls to move or shift.

On the other hand, sandy soils tend to shift and might not provide enough support, causing settling over time. If you’ve ever tried to make a dirt ball out of sand, you know that it does not stick together, or compact. This lack of compaction does not provide an ideal base for a heavy structure such as a house.

Poor building site preparation is another factor that can cause settlement. If the soil on a building site is not compacted properly, it can lead to uneven settling, where one corner of your house may drop more than the others. Compaction is not the same thing as leveling. A homesite can be perfectly level while not being compacted. Soil compaction takes time, so in an area like Charlotte where there has been a building boom, it’s a common practice to rush construction in large neighborhoods.

These building sites are also almost always clear-cut, where all of the trees on the site are removed. Where trees are taken out, there is a lot of soil disturbance because there is now space in that soil where the roots once were. If that soil is not properly compacted before construction begins, you can bet there will be settlement issues. When we are called to a home in a large neighborhood for foundation settling, we are pretty confident that neighboring homes will probably have issues as well, even if their owner hasn’t noticed them yet.

Erosion is another culprit in foundation settlement. If the land around the home is not properly graded and water runs toward the house, it can erode the soil against the foundation. This constant erosion can create space for the soil to move, and in turn, for the foundation to follow. If water runs down the foundation wall in the same pattern for an extended period, it can carve out space underneath the footers, letting them sink. Since this probably only happens along one side or corner of the house, the settlement is uneven and causes the house to be unlevel, putting a strain on the foundation and structural support. This is the reason we always backfill with gravel when performing exterior waterproofing. We discuss this more below in repair options.

What are signs a house is sinking?

So what are the signs you should look for to tell if your house is sinking? Cracks in the foundation walls are the most obvious signs. The size, shape, and location of the crack gives us a lot of information about what caused it.

Hairline cracks, or those smaller than ⅛ of an inch, are usually not a cause for concern, as they are the result of the normal expansion and contraction of concrete or bricks due to temperature fluctuations. That freeze/thaw effect can cause small cracks to form in the masonry. While hairline cracks are not a problem themselves, they need to be monitored to see if they become wider or deeper. If they do, water may be able to enter, which can cause damage to the masonry or create a bigger problem if the water enters your basement or crawlspace.

Vertical cracks run up and down a foundation wall. The most common type of cracks in our area, they usually appear shortly after a home is built and are the result of the house settling. As long as they are small and thin, they aren’t a sign of a major problem, but if they start to widen, that is a sign you have foundation movement and need to have it assessed.

Horizontal or stairstep cracks are more cause for concern, as these cracks indicate some type of structural damage. Where these cracks are located tells us what has caused them. If horizontal or stairstep cracks appear inside the foundation walls, then they are likely caused by hydrostatic pressure, where excess water on the outside of the wall is pushing against it. You may also notice water or moisture getting through the wall or efflorescence, a white or grey chalky substance on the masonry. If the hydrostatic pressure issue is not resolved, it will only get worse and can lead to severe damage to the walls. If horizontal or stairstep cracks are found on the outside of the foundation walls, it is usually a sign that the foundation is settling or shifting.

Other symptoms of foundation issues are sticking doors and windows that don’t open or close properly, baseboards or cabinetry pulling away from the walls, and cracks in the sheetrock, particularly around door and window frames. Because these signs can be caused by a few different issues, from sinking footers to damage to the home’s structural support, it is important to hire a foundation expert to determine the exact cause.

How can you fix a sinking foundation?

If a foundation professional determines that your home is indeed sinking, what are the repair options available? At HydroHelp911, we use helical piers to stabilize the foundation. Helical piers are steel shafts with a helix plate at the end that resembles a large screw. Here’s how we use helical piers for a sinking foundation. We dig out around the footer or footers to expose them. We then rotate the helical pier into the ground beside the footer using a hydraulic head on a Bobcat mini-excavator. Once the pier reaches the correct depth, which is determined by a torque rating usually specified by an engineer, a plate is attached to the top of the helical and slides under the footer. This plate supports the footer and holds the weight of that part of the house. Because the helical is driven to the correct depth and torque, it will not sink or shift and will prevent that footer from sinking any further.

In most cases, we use helical piers to only stabilize a foundation and prevent further sinking, but they can also be used to lift a foundation. While most people would think it’s best to lift a foundation back to where it was originally, that’s not generally the best practice. Unless it was caused by a natural disaster like an earthquake, the sinking probably happened gradually over an extended period of time. If we try to lift that house and put it back in its original position, we would do that in a matter of hours or days. A change in the elevation that quickly can lead to cracked floors, cabinetry, walls, or countertops. There may be times when the desired result outweighs the risk, but that’s where consulting with an experienced foundation professional comes in. Discussing the expectations and risks ahead of time is crucial to a satisfactory outcome.

I must mention that some companies use or suggest using push piers to fix a sinking foundation. We don’t use push piers because we have found that in our area, there are a couple of issues with using them. Push piers work by using the weight of your home to assist in driving steel rods in the ground until those rods reach load bearing soil. A plate is attached to your footer while the rods are being driven. When pressure is applied to drive the rod, your footer lifts up slightly, and when the pressure is let off, your footer lowers back down. The movement is slight, but your footer is constantly going up and down while the rods are being driven, and we’ve found that a lot of footers will crack under this pressure. Also, if your house doesn’t weigh enough to push the rods down to the correct soil, those rods will eventually sink again in the future. For those reasons, we do not use push piers in the Charlotte area to fix a sinking foundation. And just a side note; in our 6 years of installing helical piers, we have never had an independent structural engineer call for push piers. We think this says a lot..

How much do helical piers cost?

If you think you may need helical piers to repair a house that is sinking, you’re probably wondering how much will this cost? There are a few factors that go into determining the cost of helical piers. Take a look at the video for an explanation or keep reading below to find more about the cost of helical piers.

YouTube video

When determining the cost of repairing a sinking foundation with helical piers, one of the factors to consider is how many piers will be needed? If you are fixing one corner of your house you will need fewer piers than if you are stabilizing the entire home. Helical piers have an average cost of $1,950 per pier, so the more piers you need the higher the cost. The depth needed to reach load bearing soil is another factor to consider. If we drive down 5 feet and reach load bearing soil, it will take less time and use less material than if we have to drive down 20 feet. We never know until we start drilling how deep we will need to go to reach the correct soil, so that is a variable cost for each project.

The work space around your home will also determine how we are able to work and therefore how much time will be needed to drill the piers. If there is not enough space to bring in our mini excavator to drill the piers, or if there are obstacles such as trees or utilities in the way, we will need to dig out and drill them by hand. This will add a significant amount of time to the job, driving up the costs.

In general, it is impossible to give an exact cost or repair plan for your sinking foundation without first seeing your actual job because there are so many factors that affect the total cost. For an accurate quote, contact us to schedule a free, no obligation consultation with one of our experienced professionals.

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