Your property is indeed as tall as the strength of its foundation.
Have you ever imagined what could happen was not strong enough to hold the weight of your building?
Many factors can weaken the foundation. But the majority of structural foundation failures are attributed to settlement. You can expect your building’s foundations to settle over time. According to experts, up to 50mm of foundation settlement is acceptable.
Problems occur when the settlement is uneven. The underlying foundation soil moves unequally and results in the uneven settlement of different building sections. Differential or uneven settlement may lead to all sorts of structural problems such as foundation cracks, exterior cladding, and even interior finishes breakage.
What is differential Settlement?
Differential settlement is when the foundation of a building settles unequally, causing structural damage. Compromised soil on different sections of the foundation, together with the building’s weight, reduces the soil’s volume-air-void ratio. In return, the affected area shifts faster than the rest, causing an uneven settlement.
The soil beneath the building matures and gives in to the foundation’s pressure, allowing a variable vertical displacement of the building downwards. As a result, the frame of the structure becomes distorted. Floors slope, walls crack, and doors and windows slant or may even stop working.
A building affected by differential settlement develops fine cracks in the foundation and interior walls. The doors and windows might stick to the frame. If not careful, it is very easy to miss these small changes.
What Causes Differential Settlement
Below are a few of the prevalent causes of differential settlement.
- Soil type
Different soils have different bearing capacities. For example, expansive clay- which is found in many Missouri areas — swells during winter and spring and shrinks in summer. If the soil doesn’t shift at a uniform rate, the building’s foundation will settle unevenly.
- Poor or leaking drainage
Moisture is the main culprit of foundation settlement. Moisture saturates the soil, and when this happens, the soil loses its load-bearing capacity. Leaking water pipes on one side of the structure makes the soil give in to the weight much faster than the rest of the sections. This leads to uneven settlement of the building.
- Ground Vibration
Ground vibrations due to nearby mining activities could also cause differential settlement. Also, natural causes like earthquakes cause foundation settlement.
- Tree roots
Naturally, plants draw moisture from the soil. If your house stands close to thirsty trees, there could be problems as their roots will absorb moisture from the foundation soil, causing it to dry out and shrink. This can lead to settlement.
- Poorly compacted soils
The backfill soil needs to be adequately compacted before the foundation is laid. If it’s not compacted, the soil won’t be able to withstand the weight of your home, and this can cause it to settle unevenly.
Signs that your property has experienced differential settlement
Here are some tell-a-tale signs that your home might have settled unevenly.
- Interior and exterior wall cracking. Vertical cracks on the exterior walls or semi-horizontal cracks on the interior sides of doors and windows are signs of ongoing settlement.
- Uneven or sagging floor. This is likely to happen if the structure was erected on a pier and beam foundation. I
- Unbalanced doors and windows. Your doors and windows will be out-of-square, and you may struggle to open or close them.
How to repair stop and/or repair differential settlement
There might be dire consequences of differential settlement on a building. In the worst-case scenario, it might jeopardise the entire building’s stability, which might require you to vacate the property. It is, therefore, advisable to carry out geotechnical exploration to determine the level of damage and determine the most optimal method for remedy and prevention.
Several foundation remediation technologies can be used to remedy and manage the situation. For example;
- Jet routing. Helps manage the soil quality.
- Expanding geopolymers. Helps strengthen and stabilise the soil underneath the foundation.
- Concrete underpinning. General repairing and strengthening the foundation materials.
Micro piles. An economical method for foundation stabilisation.
