The source of leaning or off-level walls is the same as jammed windows and doors. As your house sinks, the unevenness of your home’s foundations can cause walls to lean one way or another. Leaning or off-level walls are horribly dangerous if left unchecked and unfixed. They have the potential to fall over and cause injury or worse.

If you have sloping floors, the reason is, again, unevenness in the foundations of your home due to sinking. Your floors will slope as one side of the house sinks downwards more than the other. To double check for a sloping floor, just place a ball on the floor and see if it rolls away from you. If it does, it’s likely you’re in a sinking house.

As the foundation underneath your home sinks, the floors pull away from the base of your interior walls, causing gaps to appear. The sinking of your home may also result in a floor that becomes bouncy as you walk upon it. This is likely caused by the ground pulling away from the upper parts of your home’s structure. This is dangerous because this indicates your floor’s support system is beginning to sag and weaken.

Reactive clay soil is a dense material that expands or contracts under different weather conditions. When it’s wet and cool, reactive clay soil absorbs moisture and expands but when it’s hot and dry, it shrinks. It’s the contraction of the soil that can cause the subsidence of your home.

Subsidence can also come from the introduction of new plants and trees as well as new drainage systems or altered ones. They draw more water out of the ground than usual to dramatically impact the stability of your home’s foundations.

Water erosion is often a cause of subsidence. When water pools into a specific spot in the ground too much, the soil becomes saturated and weak. If this water happens to pool into the soil under your home, your home will no longer be sitting on stable ground.

Burst, cracked and leaking pipes near or around your home can pool water. Overflowing stormwater drains, mains inlet pipes and unconnected downpipes also cause subsidence.

Thirsty tree roots and vegetation draw water out of the ground under your home. The soil becomes aerated and unstable and as a result subsidence occurs.

Sickly vegetation is especially thirsty. They have a lot of roots that suck more water out of the soil than healthy plants do.

Subsidence can occur due to dramatic vibrations in the ground. Vibrations from a nearby construction site, a main road where heavy vehicles travel all day or nearby train lines with heavy train carriages running at high speed aerate and destabilise the ground.

A nearby airport with planes taking off and landing all day can also cause subsidence.

A major cause of subsidence is poor workmanship. If contractors and builders haven’t poured trenches or compacted the ground under your home, it won’t be stable for long. Poor workmanship and negligence can result in weak, aerated and voided soil, ready to subside. The installation of poor or faulty drainage can cause water erosion which also leads to subsidence.

Although most footing designs follow Australian Standards, some are used in locations where a more unique design is required. Building a footing that isn’t suitable for the ground below, might cause subsidence.