Do houses really settle?

So do houses settle or is it just ghost skeptics' hooey? Actually, houses do settle. When they begin a downward plunge, joints and floorboards can creak, which accounts for the mysterious sounds in settling homes. And given a long enough time line, all houses eventually will settle. When a house does, it can cause serious problems. The severity of the settlement is based on a couple of factors, including how well the house was designed and constructed and the amount of attention paid to the foundation and the ground atop which the house was built.

By far, the most common reason for a house settling is improperly backfilled soil. If you've ever puttered around in a garden after spreading fresh topsoil, you've probably noticed that even after compacting the new layer of soil, you leave footprints behind. This is much the same with a house. If a builder excavates too much soil for a basement or crawlspace and must backfill it, the process requires more attention than if the basement had been dug to the correct depth.

That's because the soil -- called non-virgin soil -- has been disturbed [source: HouseMaster]. The work of centuries of compression that created naturally compacted soil, which can provide a stable place to build a house, has been undone. To recreate a suitable base, the excavated and replaced soil has to be tamped down. If it's not compacted enough again, then the house built on top of the soil will settle.

Even if the soil is well-compacted, other construction conditions can cause house settling. An excavated area over which a house will be built isn't a good place to bury construction materials like broken studs or pieces of drywall. These materials degrade over time, creating pockets that eventually collapse. This destabilizes the soil above and can lead to a house settling. The same goes for organic material (like tree stumps or limbs) which also degrades over time. Even if the buried debris is metal or another material that won't degrade while the house stands, it can still leave pockets with the same effect.

The type of soil a house is built upon also can play a role in accelerating its settlement. Clay soil is subject to changes in expansion and contraction based on the amount of water found in it at any given time. Clay expands when saturated. This causes upheaval -- the opposite of settling -- a process that produces the same problematic results for the homeowner [source: HouseMaster]. When the clay dries, it contracts and sinks, causing settling.

Water is the enemy of your home's foundation in other ways. Tree roots that grow close to a house's foundation can create cracks by searching for water beneath it. The roots disrupt the soil compaction, leading to settlement. Tree roots also invite rainwater under the house, which can further disrupt the integrity of the soil. A house without eave troughs to ferry water away from the foundation will likely settle much more quickly than one with troughs, since water can trickle beneath the foundation.

So now you know why your house settles. But how can you tell when it's settling? Read the next page to find out.

Ideally, houses are constructed to be plumb -- built evenly to a straight vertical line running 90 degrees from the horizontal plane. Think of your house's foundation as that horizontal plane. Everything rising from it, like the studs in your walls and the sides of your door frames, are meant to follow this plumb line. When your house's foundation shifts, your house is falling out of plumb and toward the horizontal plane [source: Nash].

When this shift occurs, the effects can be dramatic. Usually the first indicator is cracks in the house's masonry or concrete slab foundation. If you walk down to your basement or crawlspace, you'll find that the walls are likely made of cinder blocks. This is the masonry foundation upon which your house is constructed. It provides the support for everything else found above ground. If you find a massive piece of concrete instead of a basement or crawlspace, you have a slab foundation. Regardless of what kind of foundation your house has, if the soil beneath it shifts, cracks will appear.

Cracks aren't a dead giveaway of house settlement, however. Foundations are subject to other pressures that can lead to cracks. For example, in cold climes the seasonal freeze and thaw can cause rigid materials like cinder blocks and concrete to expand and contract, eventually leading to cracks. While cracks in the foundation aren't generally a good thing, those caused by seasonal pressures can be patched.

While some small cracks can be the result of seasonal changes, new cracks -- especially several that appear at the same time -- warrant attention. Old cracks that suddenly grow larger or any cracks that reach about one-quarter of an inch wide are also big indicators the house's weight is shifting downward [source: HouseMaster]. With wooden frame homes, walls may bow from the pressure exerted by settling since wood is somewhat pliable. Walls made of brick or stone are much more rigid and will display cracks more easily.

Other indicators of settlement are perhaps more alarming. Downward movement can result in those water and gas pipes snaking throughout the house to become twisted. You'll notice pretty fast if a water pipe becomes twisted; it can burst and flood your house. A gas pipe break is less easily detected and more dangerous. If you notice the pipes in your house bending, you've got a problem. Doors and windows are also a good indication that your house is settling. When they fall out of plumb, it can be difficult to open windows and doors since they've become angled instead of vertical.

If your pipes have burst, cracks are appearing out of nowhere in your foundation and you can't open a window to save your life, it's definitely time to call a professional. Foundation restoration companies locate the problem area beneath your house, excavate around the footing (found at the corner of the foundation), and install screws, which are like heavy-duty versions of the ones used to raise a car with a flat tire. Since the jacks are installed down to the bedrock or extremely compact soil, they act as extra support for the foundation. Additionally, subterranean foundation walls that are leaning inward can be anchored into the dirt beside them and gently pulled back into plumb.

Of course, if your home's been inspected and no telltale signs of settlement have been found, but you still hear those mysterious noises at night, then perhaps it's time to call a paranormal investigator.

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