What Causes a Home to Settle?
A simplified definition of settlement is, "structural movement that occurs when the soil below cannot support the weight of the structure above." There are many inherent causes of structural settlement, some occurring deep within the soil profile while others are nearer the surface, and it is sometimes difficult to pinpoint a specific cause for the home's settlement.
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Three of the more common causes of structural settlement are:
1) drying and shrinking of the foundation soils,
2) wetting and softening of the foundation soils, and
3) poorly compacted fill soils consolidating or compressing under the weight of the foundation.
Soils with high clay contents are particularly susceptible to volume changes with changes in moisture; i.e., they have the tendency to swell when wet and shrink when dried. If the soil moisture levels decrease significantly, clayey soils can shrink, resulting in settlement of overlying structures. Drying of foundation soils is commonly caused by farranging drought-like conditions, maturing trees and vegetation in close proximity to the foundations, and leaking subfloor heating, ventilation and air conditioning (Hvac) systems.
Excess moisture introduced to foundation soils may also prove problematic. Softening or weakening of the foundation soils can occur, reducing the soil's potential to support the weight of the home. Settlement cracks often appear as these softened or weakened foundation soils are compressed below the footings. Increased moisture conditions within the foundation soils are most often the effect of heavy precipitation or over-irrigation coupled with poor covering water drainage away from the home, which is typically clear by slow drainage or standing or ponding water adjacent to the foundation. Similarly, leaks in water lines or plumbing, or an elevated groundwater table, can also increase the moisture article of the foundation soils and lead to structural settlement.
Another common cause of settlement is poor compaction of fill soils on which the home is constructed. When most residential subdivisions are developed, the earthwork/grading phase typically involves cutting and removing soil from hilltops and then placing this material as fill within valleys to create build-able lots. When this fill is constructed with convenient material at permissible moisture and compaction levels, it can effectively support the weight of the new home. However, fill soils that are excessively dry or wet, or fill that is loosely compacted, can compress under its own weight or the weight of the home resulting in structural settlement
How Will I Know if a Home Has Experienced Settlement?
Mortar joints that are out of level, interior and covering cracking, doors and windows difficult to open and close, and chimneys pulling away from covering walls and roof overhangs are all symptoms of foundation settlement.
Out of level mortar joints are a tell-tale sign of structural settlement. Block foundation walls and covering brick veneer is commonly laid near-horizontal during construction. Therefore, the mortar joints can then be used to recognize settlement. A tool such as a laser level can help decide the extent of movement from one angle of the home to the other. Measuring from a mortar joint to the projected line or dot of the laser at several locations along the foundation wall can help with identifying both settlement trend and magnitude
Cracking in the interior and covering construction materials of the home may also indicate settlement. Stair-step cracking is common in brick and concrete block walls. If the settlement continues, vertical cracks at either the bottom or top of the wall may get wider, indicating wall rotation. Cracks extending from window and door framing are also common, both inside and covering the home. Often, the attempts made to fill or seal drywall or mortar cracks are easy to recognize due to variances in close or workmanship. When tuck-pointing brick veneer, it is especially difficult to match former mortar colors. In other cases, the fix work may not be as obvious, so directing the beam of a flashlight over the corners of doors and windows may help spot a past repair.
Observing permissible alignment and execution of doors and windows, or the lack thereof, can help with diagnosing structural settlement. Doors or windows may be out of level (racked), difficult to open or close, or separating from the framing or covering finish. If settlement is suspected, check for new caulking around windows or doors, evidence of planing on the tops or bottoms of doors to allow for easier opportunity and closing, and replacement or movement of locks or latching mechanisms on doors.
Finally, a chimney separating from the rest of the home is an certain and often dramatic indication of settlement. Chimneys are sometimes built on a foundation that is not linked to the foundation of the home.
Foundation fix - coarse Issues DRYWALL SETTLEMENT
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