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Bowed, Bulging and Leaning Foundation Walls
Diagram 6
Verifying Inward Movement: Tips for Inspections If the movement is significant, you’ll be able to see it with the naked eye. Typically, cracks are wider on the inside face. It may be helpful to use a flashlight to look into the crack. To verify the direction and the amount of movement, it is often helpful to use a four-foot level (mason’s level) or a plumb bob. Be sure to look along all house walls, both above and below grade, for leaning, bowing or bulging. Movement sometimes can be seen from the exterior (photo courtesy of Chris D. Hilton Home/Building Inspections via the “Insight by Carson Dunlop” app).
Diagram 7
can cause problems for the home’s foundation. In situations for which the only evidence of horizontal cracking is along one side of a house, the cracking often occurs on the driveway side. You can point out the possible causes to the client, but you should not be definitive and you should not be conclusive about whether the problem is progressive or not, on the basis of what you see during one visit. Vehicles also can strike and damage the above-grade part of the foundation. Watch for this along driveways, parking areas and inside garages. Having landscaping work done (including adding a swimming pool) with heavy equipment also can cause impact damage in areas away from normal vehicle traffic. Horizontal cracking due to impact damage.
Building codes have rules for how thick foundation walls of various materials must be, given certain backfill heights. There will be one set of rules for foundation walls that are laterally supported and another set for those that are not. Inspectors should check the height of backfill against the thickness of the wall, especially on new construction in which the foundation is too new to display movement (Diagram 7). Choose a reference point that can be viewed from both inside and out. Basement windows, clothes dryer vents and electrical conduits, for example, are areas that you can use to compare the height of the foundation wall against the height of the backfill. The foundation wall thickness can be checked easily at basement windows. Driveways are potential problem areas, too. If the driveway slopes down toward the house, a large amount of water will be funneled against the foundation wall. This saturates the soil against the foundation and creates a large hydrostatic load. If the saturated soil then freezes, the problem gets worse. Vehicles, especially trucks, are heavy. Heavy vehicles on a driveway 14
ASHI Reporter • July 2017
Impact damage often looks like a failure of a foundation wall due to lateral soil pressure, but usually it is more localized. In some cases, there is evidence on the outside of the impact via scraping or crushing of the exterior foundation face. If there is horizontal displacement such as leaning or bowing, then the point of maximum deflection usually will be at the above-grade level. If all of the foundation walls are similar and exposed to similar forces, you should question why there would be localized failure at one point. If it is a spot at which a vehicle can access the foundation, consider the vehicle as a possible cause (Diagram 8 on Page 16).