A sister foundation is installed by building a new wall alongside of a weakened original foundation wall. This sister wall then holds the weight that the weaker existing wall can no longer hold.
Some of the pros and cons of a “sister” foundation versus a complete foundation replacement:
Pros: Typically, a sister foundation is less expensive
The exterior of the house is not affected. This is especially important with historic structures or homes with beautiful river rock or brick foundations.
Cons: The weight of the exterior walls of the house will still be supported mostly by the original foundation.
A sister foundation is not always practical. Certain clearances are needed.
Usually, sister wall designs require for reinforcing steel in the wall, and require the construction of one-sided concrete wall forms. Once wall steel and forms are in place, concrete is pumped into the forms and allowed to set. The forms may then be removed, and the job stands completed.
Concrete cracks appear to be typical, but is not suggested that they remain ignored. Most homeowners at some point have noticed cracks in their basement or walls.
They may also recognize cracks on the garage floor, pools, or patios. Dry shrinkage, thermal movements, or other causes, like extreme temperature changes in the weather, usually cause this. Foundation and slab cracks are not only not appealing and decrease the value of your home, it can also lead into more damage and be very expensive later on to fix.
In some cases, we would need to install an additional metal plate across the crack, from one edge to another, to make sure that the crack will not widen over time.