the basics of understanding basement or perimeter foundation cracks
The basement walls are responsible for holding back the weight of the soil outside the home. The perimeter foundations on the other hand are the structural elements that are responsible for keeping the house stable above ground. Because these elements carry a lot of load, these are one of the common areas for crack propagation in the home.
Horizontal Cracks in Basement Walls or Crawlspaces
Horizontal cracks sometimes manifest on basement walls or perimeter foundations doubling as a retaining walls. Horizontal cracks that are propagating or widening in these areas are oftentimes symptoms of serious structural instabilities arising from one or several of the following conditions:
Horizontal Cracks Located in Upper 1/3 portion of the Basement Wall: A common cause of horizontal cracks in perimeter foundations is the presence of a cold joint. This usually happens when a perimeter foundation concrete is poured in multiple stages during construction. Ex: pouring 4 feet of perimeter foundation concrete, allowing it to dry and pouring another 2 feet of concrete over it. The joint between the 2 blocks of concrete then serves as a weak point wherein cracks may propagate.
Cracks in this are are also sometimes caused by unusual loading from a vehicle or equipment near the wall or frost damage. In homes located in areas with frost, standing surface or subsurface water that freezes over also exerts considerable pressure against the upper portion of the basement wall causing it to crack. This situation can easily be solved by ensuring that water from the rain gutters or lawn doesn’t pool near the perimeter of the house.
When a heavy vehicle drives by or is parked close to the basement wall, its weight pushes against the soil and this soil in turn exerts pressure against the basement wall causing it to crack. In some cases, horizontal cracks in this area are caused by impact damage by vehicles accidentally backing into the building or things impacting the building during storms and floods.
Horizontal Cracks Located in Middle Portion of the Basement Wall: Are commonly caused by vehicle and earth loading. Vehicle loading means that the basement wall may have been exposed to excessive loading from a heavy vehicle or equipment parked nearby or it is too near the driveway or road. Horizontal cracks due to earth loading may be because of basement walls that are not strong enough to support the weight of the earth behind it.
Some other probable causes of horizontal cracks at this level are hillside foundations where earth loading is made worse by frost and areas where the soils are wet frequently throughout the year.
Horizontal Cracks Located in Lower 1/3 portion of the Basement Wall: Because earth pressure increases proportionally to the depth, the force pressing against the foundations because of the earth is greatest at the bottom of the wall. This is further increased if the soil around the foundation has high water retention rate. Sometimes the cracks progresses to portions of the wall being dislocated inwards.
Other manifestations of water, vehicle and earth loading in basement walls are wall leaning, tipping and bulging. This happens when the walls are somewhat reinforced in such as way that the wall bulges, leans or tips first before displaying any cracks. This situation may also be indicative of an imminent catastrophic failure so immediate attention from a qualified foundation repair specialist is needed.
Vertical Cracks in Basement Walls or Crawlspaces
Should there be any seismic activity, vertical movement or settlement of the house, the basement walls and perimeter foundations are usually the first places where you will find some indications. To read more about these type situations causing vertical cracks, please read this article.
Diagonal or Step Cracks in Basement Walls or Crawlspaces
Diagonal or step cracks in basement walls often manifest when there is settlement or frost heave /lensing under the foundation. In rare cases, these types of cracks are caused by creep where a portion or the entire wall slides away from its supports without bulging, leaning or cracking. This is a dangerous condition especially if the wall is made of brick masonry as the wall bond courses may be broken and the wall is in danger of collapse.
Because cracks in the basement, crawlspace and perimeter foundation areas are more often than not structural in nature and affects the structural stability of the whole house, it is best that you should consult a qualified specialist capable of assessing the cracks and suggesting an effective solution that will not only cosmetically repair the crack but also address the forces causing these cracks in the first place. Call Sinai Construction, the Los Angeles Crack Repair Specialist today for a consultation.
