Foundation Cracks
Foundation cracks can be a serious defect or they can be of no concern hopefully the following will help you recognize the difference when looking at your own home or one you propose to buy.
As concrete dries it shrinks, which often causes hairline cracks.
The faster it dries, the more it shrinks
The higher the water content in the mix, the more it shrinks
Shrinkage cracks normally develop at windows, doors, beam pockets or other penetrations. Usually these cracks are hairline cracks, no bigger than the thickness of a dime and no cause for concern.
Shrinkage cracks are the most common types of cracks. They will be found on most homes.
Larger cracks may or may not be a concern but should be checked by a qualified individual. The Alberta New Home Warranty Program Performance Guide states: “Cracks are not unusual in concrete foundation walls. Such cracks greater than 1/8 inch are considered excessive.”
The main concern is Structural Movement in the foundation.
If there is displacement, the concrete will be uneven from one side of the crack to the other. This movement usually indicates external pressure on the foundation wall, which must be investigated, or it could be that the wall was damaged during construction.
Horizontal cracks in a foundation are more uncommon but can be stabilized without major expense as long as the cause is not ongoing and there has not been large displacement in the foundation.
There are a number of factors that will cause horizontal cracking or movement.
Backfill heights:
Frost, heavy traffic and tree roots:
Movement in the foundation can be caused by any number of factors. Larger type cracks in foundations are caused by settlement in the footings or pressures from below forcing the footings up or pressures from the outside of the foundation. Foundation walls (footings) that have heaved upwards are caused by inadequate frost protection for the footings or expansive soils.
A high clay content in the soil below the footing, together with water can cause extreme damage to foundations. The source of the water must be found and eliminated.
The amount of movement and age of the structure should always be taken into consideration.
Some examples for foundation movement are as follows:
Soil types and water pressure:
Frost pressure, Lot Configurations and Excavation Differences:
Movement in a foundation wall is usually more serious and should always be analyzed by a professional.
Common Foundation Repairs
These types of repairs need to be designed and approved by a person specializing in foundation repairs preferably a structural engineer. These repairs can be quite costly.
Wall or Footing Settlement
Mud jacking or hydraulic jacking and under pinning of the footing may be required to stabilize the foundation that is dropping or settling.
Displaced foundation wall cracks may need to be reinforced or stabilized.
The vast majorities of foundation cracks are of no concern, but should be investigated and reported on by an expert. The expert’s written report is not only important for your purchase and peace of mind, but to show to a future buyer when you sell.
