A Glossary of Terms Surrounding Foundation Repair and House Leveling
Catch Basin– A hole, dug at a distance from the foundation, then filled with gravel, sand, or other porous material. A catch basin is designed to work with a french drain to drain water away from the foundation. Water held in a catch basin evaporates or is absorbed into surrounding soil.
Clay – A naturally occurring mineral that is present in tiny particles. Clay traps and holds water within its molecules causing expansion or “swelling” of the soil. When water is withheld clay particles contract or “shrink”. Clay is also called Expansive Soil or Gumbo.
Concrete Slab – Concrete that is typically poured in a single piece and serves as base support for a building. A slab foundation is reinforced with steel rebar and/or steel stressed cables, and other methods. Slab foundations may have footers made of the same materials. Required dimensions and components of slabs and footers may be dependent on local building codes. A concrete slab sits directly on surrounding soil. Also called Slab On Grade.
Differential Moisture Content – A frequent source of foundation damage is the differential expansion of soil under and near the foundation. Moist soil is adjacent to dry soil. Differential Moisture Content can be caused by low areas that hold water longer than surrounding areas, watering of lawns and garden beds, absence of gutters which direct water away from the foundation, water leaks, etc.
Footer or Footing – An object, usually part of a concrete slab, that provides support for the building’s foundation Footers help distribute the weight of the foundation and building evenly throughout the entire foundation.
French drain – Perforated pipe or gravel bed installed underground to catch and divert water from the foundation. A french drain is graded to drain the accumulated water away from the site.If land is flat a catch basin and discharge pump may be necessary to contain water.
Grade – Ground level, or elevation at any given point. Excavation or building up then leveling of soil that will support a building’s foundation. Correct grading causes water to drain away from the building’s foundation.
Mud Jacking – Procedure in which grout (typically a sandy loam, water and cement mixture) is pressure pumped under the foundation in multiple locations. Mud jacking is best used for small areas like driveways, sidewalks etc. It is not a good solution for a home or business foundation. The reason is that the applicator has no control over where the grout goes after leaving his equipment. The liquid material takes the path of least resistance so it can come up through the foundation in low areas and pipes that may not be firmly joined. In addition the back pressure from application can cause separation of plumbing pipes coming through the foundation. Because application is uneven results aren’t predictable. Once the grout has set up it is as difficult to remove as concrete. Mud jacking also tends to be a temporary method of repair. In order for the grout to hold the foundation in position it depends on the soil beneath it to remain in place. If the soil moves due to loss of moisture then the grout will not be able to hold the load.
Piers or Piering – Multiple steel posts are driven through unstable soil to bedrock. Then hydraulic jacks are used to stabilize the slab. The slab is held in place by the pier and the special bracket, attached to the pier, that holds and supports the slab.
Rebar or Reinforcing Bar – Ribbed steel rods that are placed in forms of foundations, concrete walls, and footers. Concrete is then poured into the forms with rebar in place. Rebar strengthens the concrete.
Root Barrier or Barricade – A root barrier is an impermeable material that is inserted into the soil driven into the soil to a depth of approximately 3 feet. The barrier prevents tree roots from growing under a home’s foundation where they may rob the soil of moisture. Root barriers may be made from fiberglass, plexiglas, or other materials.
Slab On Grade Foundation – A building construction practice in which the concrete foundation slab is formed from a reinforced form (typically a wood frame) set into the ground. The concrete is poured into the form.