What do the Millennium Tower in San Francisco, Big Ben in London, and the Leaning Tower of Pisa have in common? All these buildings lean to one side. In each case, the cause is a sinking foundation.
Differential settlement is the technical name for this problem. Many of the buildings have become famous tourist attractions but differential settlement for a homeowner in Kansas City or St. Louis is a serious problem.
Differential settlement can result not only in a building leaning to one side but can also lead to serious structural damage. In extreme cases, the home can become unlivable.
Uniform Settlement vs. Differential Settlement
Most foundations will show some settlement and the level of settlement (vertical displacement of the soil) depends on the shape and size (surface area) of the foundation, the weight of the foundation, and the land it is built on. Bedrock will show little or no settlement whereas soil will show much more settlement. This type of settlement is called uniform settlement and it is usually not a problem.
Differential settlement is when one part of the foundation sinks more than the rest of the foundation. This problem can appear not long after construction or it may appear after many years. In some cases, uneven settlement can result in a building that’s leaned over but is not structurally compromised. Very often, however, it will cause damage.
What Can Cause Differential Settlement?
Some of the causes of differential settlement include:
- Tree roots can damage foundations directly, but they can also cause differential settlement by drawing the moisture out of the soil under one side of the foundation.
- Leaking pipes causing part of the ground under the foundation to become waterlogged.
- Large excavation near a structure can cause some soil movement under the foundation.
- Vibrations, perhaps due to nearby construction work or the proximity of a busy road.
- Differential drying of soil surface layers.
- Natural causes like flooding or drought.
- Anything that changes the moisture content of the soil can potentially cause problems.
How to Recognize the Signs of Differential Settlement
For a typical house, some signs of differential settlement include cracks on the walls. Sometimes the cracks are just the plaster cracking. These do not threaten the integrity of the structure. However, other structural cracks can appear along walls or near doors and windows; they are an indication that the foundation is shifting.
Unlike the mesh-like shape of plaster cracks, structural cracks are more linear. They could be at an angle of around 45 degrees, or they may be vertical or horizontal. They can appear on inside walls as well as outer walls.
Other signs of uneven foundation sinking include doors and windows sticking, sloping floors, chimneys pulling away from the house, and a leaking roof or basement. It is best not to ignore these signs, as with many other situations, leaving the problem can make it more difficult to fix. If you see these signs in your home, contact a professional, as this is not a do-it-yourself kind of job.
So, what can Kansas City or St. Louis homeowners do about this problem? They simply need to contact an expert to underpin their sinking foundation with piers. Below are the different kinds of foundation piers:
Push Piers: Also known as resistance piers, push piers are steel systems that are driven into the ground to stable soil layers and then hydraulically lifted until the concrete foundation is level again.
Helical Piers: This type has threaded shafts, which are a bit like giant screws. Similar to resistance piers, helical piers need stable ground to hold them.
Slab Piers: These piers are used specifically for homes with a slab foundation. They are installed and function the same way to permanently stabilize and help lift the foundation.
In most cases, piering doesn’t require extensive excavation or the replacement of the entire foundation block. The installation also won’t involve heavy construction equipment. If piering sounds like the right solution for your sinking foundation, contact Foundation Recovery Systems to schedule a foundation repair inspection today. We’ll provide you with a free quote along with recommendations to fix your structural problems.