Your building’s strength depends on the stability of its foundation. Unfortunately, variations in the strength or bearing capacity of the soil under the foundation can cause its base to sink. This is known as foundation settlement. The amount of settlement depends on the structure’s weight and the characteristics of the soils beneath it.
If the settlement is uniform, it’s less likely to be disruptive. But if one section of the foundation sinks more than the other (differential settlement), there’s bound to be serious problems. Read on to learn more about the ins and outs of differential settlement.
What Is Differential Settlement?
Differential settlement is the uneven settling or sinking of a foundation. It happens when one part of your home’s foundation settles at a faster or slower rate than the other.
What Causes Differential Settlement?
Construction flaws aren’t to blame. What’s responsible is the soils beneath your foundation. Different soils expand, contract, and shift unevenly, resulting in your foundation settling at an uneven rate.
But that’s not the only thing that causes differential settlement. In some areas, outcropped or shallow bedrock means part of the home rests on stable ground and the other in loose soil. Over time, the part that rests on the soil naturally settles under the structure’s weight, whereas the part that rests on the bedrock remains in place.
Problems Associated with Uneven Settlement
Whether settlement happens in a few months or takes a couple of years, the problems that arise remain pretty much the same. You’re likely to experience multiple issues such as:
- Sticking doors and windows
- Wall and floor damage
- Distortions or warping on your building’s frame
- Foundation cracks and deterioration of slabs
- Structural instability that makes your building unsafe
Signs of Differential Settlement
When a foundation doesn’t sink uniformly, the wood framing may warp and throw your windows and doors out of their frames. You’ll also notice cracks on your concrete slab or foundation walls and breaks in the seams between drywall panels.
While cracks are normal and expected over time, if they are wider at the top than at the bottom, this is a sign the foundation is settling unevenly. In severe cases, differential settlement may throw your floors out of level such that when you place a marble on the floor, it will begin to roll.
Most of these signs are easy to spot. Contact your local foundation repair expert in Raleigh or Winston-Salem, NC, to find out how serious the problem is and how you can salvage the foundation.
Restoring a Settling Foundation
Your sinking foundation needs to be underpinned using piers and there are a few ways to do this. What this does is transfer the heavy load to the stable bedrock and stabilize the foundation.
Helical piers: Also known as screw piles, helical piers consist of a central shaft with several helix-shaped plates. These piers are versatile and great for supporting light structures such as porches.
Push piers: Mechanically driven into the earth, push piers help pass your structure’s weight to the stable bedrock. They’re installed close to the footings and secured in place using brackets. These systems are easy to install and cause little disturbance to the landscape.
Slab piers: This type is designed to stabilize or raise sunken slabs. They’re driven into the ground and down to the load-bearing soil. Grout is pumped to fill the gaps under the slab before concrete is poured over the holes.
How to Prevent Differential Settlement
You can avoid settlement and forestall problems by asking a structural engineer to analyze the soil under your foundation. Ideally, the dirt should be non-expansive, with very little silt or clay soil. Your structural engineer will tell you whether the ground on which you’re building is stable or needs some adjustment. Worried that your foundation is sinking? Contact the experts at Tar Heel Basement to schedule a free foundation inspection and repair quote. We can repair your foundation problems, including differential settlement, before they cause serious structural damage.