Foundations and Crack repairs
The foundation is portion of the buildings structure that transfers the weight of the building into the ground and they can generally be broken down into two categories.
Shallow foundations
Shallow foundations transfers a building’s weight load to the earth near the surface. Types of shallow foundations include spread footing foundations , mat-slab foundations , slab-on-grade foundations , pad foundations, rubble trench foundations and eathbag foundations.
Shallow footings are generally embedded into soil at about a meter deep. There are two common types, one of them being the spread footing which consists of pads or strips that extend below the frost line and transfers the weight of the building to to soil or bedrock. The other being the slab on grade footing which transfers the weight of the building to the soil through a concrete slab poured directly on the surface.
Deep foundations
A deep foundation is determined by the depth it is embedded into the ground. There are several reasons an engineer would recommend a deep foundation over a shallow one but the most common would be poor soil at shallow depths. Deep foundations can be made out of timber, steel, reinforced concrete and pre-stressed concrete.
Footings
Footings are designed to carry the load of the future building with limited settlement by a geotechnical engineer but the footing itself is designed by a structural engineer. The primary concerns of designing foundations and footings are the bearing capacity and settlement. It is very important that a foundation does not carry a load beyond it’s bearing capacity or it will fail. When considering settlement, total settlement and differential settlement are generally considered. Differential settlement is when one part of the foundation settles more then the rest.
Foundation cracks and repairs
Over 95% of foundation cracks do not pose any structural threat to the building. Vertical or diagonal cracks may only pose a water seepage issue that is not difficult for experts to fix. Concrete cracks for wet and leaking foundations, the preferred repair method is urethane foam injection. Urethane foam is easily injected into the crack and expands throughout the void which fills the crack and should prevent any future foundation leaks in that particular crack.
Foundation cracks that may pose a structural threat however, the repair is best suited for pressure injection epoxy. Not only will the epoxy fill the crack with a high strength adhesive that “welds” the foundation together . It also restores the walls structural integrity. Epoxy successfully eliminates wall movement during normal expansion and contraction of the soil during seasonal cycles.
Nathan Pile
Napoleon Home Inspections
