Can the Footing Be Reinforced on an Erected House?

Common Types of Footing

• The choice of footing type is wide and is influenced by factors, such as the predicted weight of the finished building, type and height of the walls that will rest directly on the footing, lay of the land to be built on and available budget. Soil compressibility and the potential for settlement, properly called the bearing capacity, also are factors.

  The simplest and, therefore, typically the most cost effective footing type is concrete pad, also called spot footing. Holes are dug at strategic points across the area where the building is to be constructed. A reinforcing cage is slipped into the holes and then concrete is poured to ground level. The holes typically are around 2 feet square and are located where load-bearing structural members, such as the frame of a timber house, will reach the ground. Strip footings also are common. A strip footing can be built in a relatively narrow trench dug for the purpose, or in a combination of a trench below grade and a shuttered enclosure above grade. Both systems are filled with reinforced concrete. If the latter arrangement is used where termites are abundant, the shuttering must be removed before construction can proceed.

Symptoms of Failing Footings

• When footings begin to fail, the building resting on them will let you know. Cracks appear in walls, but this initially may be disguised indoors by the gypsum panels used typically to finish interior walls. Other common symptoms include doors that jam closed or refuse to close, and bulges appearing in formerly flat floors.

Piering

• Piering essentially is the installation of support pillars, or piers, under the building that offer additional support to that of the original footing. Helical piering, also called helical pile foundations, consists of rods with helixes of thread welded onto them. They are screwed into the ground until the desired load-bearing capacity is achieved, after which brackets are attached to the walls that transfer the weight of the building to the piers.

Slabjacking

• Slabjacking is a process that results in the original footing being returned to its pre-fail location. An extremely viscous liquid grout is injected under the footings that floats them upward, then sets to hold them rigidly in place.