Foundation Repair Terminology

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Foundations and the problems that impact them can be confusing. Olshan knows that when homeowners and commercial property owners are facing potential foundation damage, the prospect of securing the right repair solution can seem daunting. Understanding some of the basic terminology involved in foundation repair can help. This FAQ was designed to help you familiarize yourself with the basics of the foundation repair process. Below you will find a lot of the common terminology you can expect to encounter when dealing with a foundation project.

Active Zone: The value of seasonal moisture variation.

Aeolian soil: Soil that has been deposited by the wind

Alluvial soil: Soil deposited by running waters.

Basal spacing: The distance between individual or molecular layers of the clay particles

Baseboard water channel:
An interior basement drain unique to monolithic slab foundations. Monolithic basement slabs should not be broken out like concrete “floating” slabs.

Batter pier: A pile driven or a pier cast at a vertical incline.

Bell bottom: Enlarged bottom end of an augered pier to increase load bearing capacity. Typically limited to 3X the shaft diameter.

Bentonite: Clay used as a heavy slurry to prevent the earth from sloughing into a drilled hole, or to aid in the removal of cuttings during drilling.

Cable Lock™ ST Plus: Olshan’s trademark hybrid foundation repair system that combines the durability and strength of concrete with the ability of steel to reach desired depths regardless of soil conditions. The pilings are then locked together with steel cable.

The diameter of tree foliage. Also known as “drip line”.

Capillary fringe: An area that contains capillary water that originates from the water table.

Capillary pressure:
With references to soils, the negative water pressure at points above the water table. Sometimes defined as the difference between air and water pressures in pore space.

Capillary rise: A measure of the height of water rise above the level of the free water boundary. Capillarity is impeded by the swell of clay particles upon invasion of water. Finer soils will create a greater height of capillary rise, but the rate of rise is slower. The result of surface tension.

Carbon fiber strips: Used to reinforce a poured or concrete block wall affected by bowing, by isolating movement in the wall.

Clay: A soil that has the finest possible particles and often possesses the capacity for extreme volume changes with differential access to water.

Concrete piling:
A slender column constructed of concrete and containing steel rebar in its center. The piling is driven into the soil to a predetermined depth and used as a support for a building?s foundation.

Drilled-in caisson: An open-ended pipe driven into rock. It is cleaned out and a socket is drilled into rock to receive a steel core, then, the socket and pipe are filled with concrete.

Drilled pier: A concrete pier or pile cast in the place in an augered hole, which may be belled at the bottom. Particularly suitable where soil is dry and hole will stand open. Otherwise, casing is required.

Driving cap: A steel cap placed over a pile to prevent damage.

Earth anchor: A steel shaft containing one or more helixes that is screwed into the earth to provide a retention system against uplift forces.

Elevations: Measurements taken by instrument to establish grades.

Epoxy crack injection: Cosmetic wall repairs that can conceal cracks and reduce moisture but do not provide long-term foundation stability.

Expansive soil (expansive clay): Any soil that expands and contracts due to the presence or absence of water can be considered expansive. Clay soils, like those found throughout Texas, are examples of expansive soils. The clay soils soak up large amounts of water, thereby expanding the soil. This then exerts pressure onto a home’s foundation. When the soil dries, it contracts and the foundation is shifted again.

Fill: Soil added to provide the level or desired construction surface or grade. Gravel can be substituted for dirt to decrease hydrostatic pressure on basement walls.

Footing: A member, usually concrete, that distributes the foundation load over an extended area and provides increased support capacity on bearing soil.

Foot: The lower end of a driven pile.

Foundation: The part of a structure in direct contact with the ground that transmits the load of the structure to the ground. The most common forms found in the US are slab on grade, pier and beam, block and base and basement foundations.

French drain: A perforated pipe installed in a cut to intercept and divert subsurface water. The cut is below the level of the intruding water and is graded to drain the water away from the structure. Sometimes a catch basin and discharge pump are required if sufficient natural grade does not exist.

Frost heaving: Expansion that results when a mixture of soil and water freezes. Upon freezing, the total volume may increase by as much as 25%, depending on the formation of ice at the boundary between the frozen and unfrozen soil.

Grade: The level of ground surface. Also, the rise of fall per given distance.

Gravity discharge: Uses a natural or man-made slope in landscape to discharge water near the foundation.

Grouting: An operation where material is injected to penetrate and permeate a relatively deep soil bed. The purpose is to decrease voids or permeability, increase strengths of the soil, or, on occasion, impede organic decay. Grouting is often used in sinkhole remediation.

Gumbo clay: Highly plastic clay soil from the southern and western United States.

Heave of pile:
The uplift of earth between or near piles caused by the displacement of soil by pile driving.

Helical pier: Often used when soil conditions are unfavorable, a helical pier is a steel shaft shaped like a corkscrew that can be driven into the soil to provide support for a foundation or to adjust a shifted/sagging foundation.

Hybrid piling: Olshan’s unique foundation technology that combines concrete and steel to provide the best structural stability. It installs without the use of heavy equipment and can penetrate rocky soils.

Hydrostatic pressure: Ground water pressure that builds up and compromises structural integrity of a foundation.

Interior floors: Floors that are supported by the girder-and-joist system of a wood substructure. The system is in turn supported on piers and pier caps or piles and pile caps.

Ionic bond: Chemical bond resulting from the complete transfer of electrons from one atom to the other.

Lateral support: Batter piles or reinforcement to resist lateral forces on piles or footings.

Masonry block wall: Brick basement wall, generally easier to repair than poured basement walls.

Minipile: A pile with a very small diameter-to-length ratio, that transfers loads almost entirely by skin friction.

Moisture barrier:
A means of maintaining moisture content beneath a foundation consistence of an impermeable barrier extending to some depth and in close proximity to the perimeter beam.  Moisture barriers are commonly found in crawl space encapsulation, basement wall waterproofing and drainage projects.

Mudjacking: A process whereby a water and soil cement or soil-lime-cement grout is pumped beneath the slab, under pressure, to produce a lifting force that literally floats the slab to desired position.

Negative friction: The effect on a pile of settling soil that may grip the pile and add its weight to the load to be carried by the bearing strata.

Osmosis: The transfer of water through a semipermeable membrane. The increased pressure caused by the diffusion of water is referred to as the osmotic pressure.

Permafrost: Refers to a condition where the subsoil remains continuously frozen.

Pier and beam:
A design where perimeter loads are carried on a continuous beam supported on piers drilled into the ground, ideally, to a competent bearing soil or stratum. Interior loads are carried by isolated piers in a grid pattern.

In general, concrete poured into circular holes that are normally of larger cross-sectional area relative to length. Shafts are generally extend through marginal soils to either rock or competent bearing material. For residential and lightly loaded structures the optimum pier diameter has been established to be 10 – 12 inches.

Pile: Long, slender wood, steel, concrete or blended members usually driven in groups or clusters. They may also be poured concrete, which gives rise to the gray area of differentiation between piles and slim piers.

Piling: A pile or pier connected to a structure by one or more ties to facilitate lateral support and resist uplift. Also used for load testing.

Pile cap: A pile cap sets atop the concrete piling and is used to help disperse the weight of the foundation. This helps ensure the support system can handle the load, keeping the foundation from sinking into the soil.

Poured basement walls:
A standard slab wall. Susceptible to cracks from hydrostatic buildup.

One or another variety of concrete foundations, generally supported entirely by surface soils. It probably constitutes the majority of new construction in areas with high-clay soils.

Soil stabilization: A procedure for improving the natural soil properties to make them a more adequate base for construction.

Spacers: Spacers are placed between the pile caps and the foundation to provide building support.

Steel pier: A slender column constructed of steel that can be driven deep into the soil, to the point of refusal, for foundation support.

Stack effect: Phenomenon that pulls warm air from the lower levels of the home, up-and-out through the upper levels of the home. In crawl space and basement homes, these means the indoor air consists of the same air coming from the basement or crawl space. Humidity, musty smells and allergens are often funneled up into the living space.

The force at a point in a soil mass that is due to the weight of the soil above the point plus any applied structural load.

Sump pump: A device used to forcibly discharge intrusive basement or crawl space water out and away from the foundation.

Sure-lock: Olshan’s trademark locking system that secures the pilings together for the strongest foundation support.

Wall anchors: Cost-effective, minimally invasive wall repair system that uses an interior wall plate attached to an anchor on the exterior of the home an designed to stabalize foundation walls by reducing pressure.

Wall braces: Supports bowing or buckling foundation walls from inside the basement without disturbing the outside of the home.

Wall shield: Liner used in basement homes to reduce air quality problems in brighten interior walls.

Water leaks: Water from any domestic source that accumulates under the foundation.

Water table: The upper surface of water saturation in permeable soil or rock.