Glossary of Foundation Terminology

Active Zone

The active zone refers to the depth of soil instability or movement, usually due to moisture variation. It is also called the Seasonal Zone.

Base & Block Foundation

This is a home that was built traditionally pre-1950. This home is built without a grade beam. The entire under-structure depends on footings, poured sonitube piers or in most cases beau d'arc stumps.

Builder Piers

When the grade beam on a Pier & Beam home is poured, builder piers are poured beforehand at a spacing of 4–8 feet apart and at an average of 3–4 feet down. These piers assist in holding the grade beam in place. Due to their low level of placement, they can fail and additional pier supports become required.

Catch Basin

The inlet used to take water in to direct them into a 4" or 6" pipe when used to control water. These are usually 9"x9" to 12"x12".

Clay

A naturally occurring earthy mineral that is plastic when wet but becomes permanently hard when heated. Clays are formed by the weathering of feldspathic rock and are composed of hydrated aluminum silicates. Clay exhibits significant volume expansion when mixed with water and significant compression when water is withdrawn.

Concrete Breakout

This is the term used when the location of the pier is obstructed by some form of concrete (i.e. patio or walkway).

Drilled Pier

Until the early 90's, this was the main method used to support a failing foundation. A hole is drilled at an angle to a pre-determined depth under the slab — usually no more than 10 feet down — rebar is formed in, an 18" cap is formed on top, and the hole is filled with concrete mixed with a curing agent. This pier carries a 3–10 year warranty on average and is expected to fail if the underlying causes are not addressed.

Elevation

Elevation is a series of measurements to determine the difference in height between a central point and other points.

Engineer's Report

When a home is repaired, a 3rd party Engineering Report should be ordered to assure you that the plan of repair set into place is accurate and will correct the foundation problems adequately.

Footing

A footing is a lower level pier support used to support non-load bearing areas like patios, porches or small enclosed additions. They are less expensive on average and will not cause structural damage when placed under small areas that do not have a thick beam.

Foundation

A home foundation is that part of the structure that is in direct contact with the ground. The foundation transmits the weight of the entire home and itself to the supporting soil.

French Drain

A drain used to collect water that migrates underground. French Drains are usually dug 36–48 inches deep. 1¼" river rock is placed at the bottom of the trench and a 4" corrugated pipe is placed over this rock. The trench is filled with river rock to approximately 4–6" below grade, then topped with soil and/or sod.

Grade Beam

The grade beam is the concrete support that goes around the perimeter of a Pier & Beam foundation. It is poured on average 18–20 inches below soil grade and is reinforced with rebar for additional support.

Grading

Grading describes the direction water would flow on the soil. Traditionally, you want soil graded away from the house at a rate of 1 inch of drop per foot of grading.

Interior Pier

When a slab foundation has dropped excessively and interior elevations must be raised, an interior pier is placed under a load bearing wall or interior beam support. Once in place, the hole is filled with dirt and capped with concrete.

Lifetime Warranty

In the state of Texas, a lifetime warranty is 20 years — no more, no less. This does not mean that the contractor will not warrant the goods or services for longer; that's just how long the state recognizes the warranty.

Mud-Jacking / Pressure Grouting

When a home is repaired with a lift in excess of 2", a gap is created under the slab. Mud-jacking fills these voids and adds additional support under the foundation using a cement/soil mixture pumped under pressure.

Non-Obstructed Pier

A pier that can be placed in the ground without any additional work (i.e. concrete removal, deck removal, etc.).

Pier & Beam Foundation

A foundation method using beams, joists, under-structure supports and often a grade beam. This type of home is raised off the ground allowing access to plumbing and wiring. The existence of wood-rot is likely if the home does not have adequate drainage or if a plumbing leak exists.

Plumbing Report

When a home is repaired, a plumbing report should be included to prevent problems from not being aware of existing damage. Reports are done before and after repairs on slab repairs, and only after repairs on pier & beam repairs, testing both high pressure and sewage lines.

Positive Drainage

Positive drainage describes soil laid around the perimeter of the home so water moves away from the house. Minimum grading is a 2" drop over 2'. This prevents water from ponding around the perimeter and helps control the moisture content of the soil.

Pressed Pier

An alternate repair method that emerged in the early 90's. A pressed pier is 6–8" wide, made up of 12" pre-pressed pilings pressed into the ground using a hydraulic press to refusal — bedrock, hardpan, or a large boulder. Average depth in DFW is 12–20 feet, making it less vulnerable to volatile soil.

Retaining Wall

A retaining wall supports eroding soil in volatile areas. They also help move water away from an affected area with the installation of a French drain at the base, and provide additional support to foundations built on fill dirt.

Root Barrier

Used when large trees are placed too close to a slab foundation. Trees in DFW require 50–500 gallons of water per day and their roots draw moisture from under the slab. A trench is dug along the slab, roots are cut, and a 30" steel barrier is placed to prevent future root growth under the house.

Settling

Settling refers to a process where part of a home's foundation has moved below its original elevation. It usually results in interior and exterior cracks and is caused by a loss of mass under the foundation.

Sill Plate

The 2x4 or 2x6 piece of wood placed along the top of the Perimeter Grade Beam on a pier & beam house. When subjected to excessive water, the sill plate will deteriorate and require replacement. Deteriorated wood can become compressed and cause cracking in sheetrock.

Slab Foundation

In Texas, slabs are generally cast with perimeter and interior beams designed to resist differential soil movement. Texas slabs are typically reinforced with rebar and/or post-tensioned cables. Most homes built in Texas are built on concrete slabs.

Soaker Hoses

Recycled rubber converted to a hose which allows water to pass in a low-volume, low-pressure form to evenly distribute moisture over a large area.

Sonotubes

In most pier & beam foundations, poured sonitube piers are used to support the beams under the house. They are placed 12–18" under soil grade with rebar inside for additional support. They are far superior to pad supports.

Sump Pump

A sump pump is used with surface drains and French drains when water being moved to a common point is lower than the designated outlet. Sump pumps are automatic and pump accumulated water to a designated area such as a street or lower spot.

Surface Drain

A surface drain moves large amounts of water that collect on top of the ground. A 4" pipe is placed underground with collection boxes at optimal areas. Down spouts from rain gutters are often tied in. These are the most common type of drain used to correct improper drainage or grading.

Transferable Warranty

A warranty that stays with the product and only the owner of the warranty changes. The transfer usually has a fee charged for administrative expenses.

Underpinning

The process of modifying an existing foundation system by extending it to subsurface strata that is deeper and more stable than the near surface soil. Methods include construction of footings, stem walls, driven piling or drilled piers.

Upheaval

Upheaval refers to a process where part of a home's foundation has moved above its original elevation. It usually results in interior and exterior cracks throughout the home.

Vent — Powered with a Hydro-Stat

Many pier & beam foundations have inadequate ventilation. A powered fan installed at an existing vent location draws air from under the home creating cross-ventilation, which helps evaporate moisture in the soil, concrete and wood. A hydrostat allows the fan to turn on only when moisture levels reach pre-determined levels.

Ventilation

Proper ventilation helps maintain the desired climate in the crawlspace. Texas State Code requires 1 square foot of ventilation per 150 square feet of first level pier & beam foundation.

Water Leaks

Water leaks are a major problem for home foundations. Usually resulting from leaks in the plumbing system, they can contribute to water accumulation under a home, causing upheaval (swelling and expansion of the soil) and excessive settlement.