Cracks are an inescapable, undesirable feature of many buildings. Some cracks are the result of wear and tear, while others are related to construction or design defects. Expansion and contraction of soils, consolidation of soils, vibration, wind, snow loading, overloading, and impacts all may cause cracks. Insurance coverage for repair of cracks may be extended or denied depending on determination of the cause of the crack.
Frequently, cracks form between building sections, such as when new additions settle as a result of soil consolidation at the new foundation. This tends to stress the interface between the two buildings, causing cracking at the interface. Because of the discontinuity between the old and new additions, soil movement from expansion and contraction also can generate cracks.
Other soil-related influences may lead to the formation of cracks. Ground water can cause soil erosion and reduction of soil compressive strength, reducing load-bearing capacity of the foundation, stressing and cracking building materials. Soil voids from improper or insufficient compaction of the subsoil have similar effects. Different soil types have characteristically different bearing strengths and can cause foundation movement-related cracks.
Another potential cause of cracks is the failure of structural members. These can occur for a variety of reasons, such as a defect or deterioration. This stresses other building components, promoting crack formation. An example of deterioration of the support structure would be when a rotten set of floor joists deflected sufficiently to crack wallboard in the room above.
A partial collapse of a foundation is common among older stone foundations. Mortar deteriorated and stones fell into the basement area. The loss of structural foundation support caused cracking of drywall in the building's interior, another form of deterioration.
A typical garage floor slab X-pattern crack is a symptom of up and down soil movement over time. Chunks of dust and concrete debris have become embedded in the cracks, suggesting that they formed over a long period. This is an example of settling.
Flaking and fracturing of brick and mortar joints can cause structural instability and further cracking in the brickwork that is not deteriorated. Typically, this type of cracking occurs over the long term, and is a form of deterioration.
Another type of crack is that in wallboard at a corner feature. The crack tip can be very thin with increased thickness at the initiation point, the corner. Dust and paint in the crack at the initiation point suggest that this crack developed over time. This is a result of settling.
Because of larger amounts of insulation in attics in recent years, the lower cords of trusses tend to dry out and shrink, causing uplift of the trusses in the middle. Sometimes the cracking of wallboard can occur in the center of the home as a result of truss uplift. This can generate unsightly cracks in wallboard unless the installer took care to allow more flexure of the wallboard in areas of large deflection. This is a result of improper construction.
Sometimes, severe cracking can occur in the roof rafters of a residential home. The framing lacked collar ties, which over-stressed the frame connection. Collar ties are boards that connect opposite rafters at about two thirds the height from the floor to the ridge board. This is considered a construction defect.
Soil and water pressure also may cause inward deflection of walls and impending failure. Figure 8 illustrates an indicator of this, a horizontal crack in a block wall about halfway up. In this case, water drainage toward the foundation caused an excessive hydraulic load. Lack of maintenance of gutter drainage and grade near the wall increased hydraulic loading against the wall over time.
Claims involving cracks in buildings often require technical analysis to determine the causes of the cracks. Any analysis must consider the histories of the buildings, such as age, last roof replacement, and dates of additions or remodeling. Additional information, including old photographs, unusual events around the loss dates, and repair receipts, are helpful. Once the cause of the crack has been determined, coverage decisions may be made based on determinations of settling (typically denied), deterioration (typically denied), explosion (typically extended), and vehicle impact (typically extended).
Charles C. Roberts Jr., Ph.D., PE, is a consulting engineer based in Big Rock, Ill. He is primary author of the reference work "Technical Notebook: Forensic Aspects of Claims," released by ClaimsBooks.
© Arc, All Rights Reserved. Request academic re-use from www.copyright.com. All other uses, submit a request to TMSalesOperations@arc-network.com. For more information visit Asset & Logo Licensing.