Glossary of Foundation Terminology

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Definitions-

 

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” x 12”.CLAY - Clay is 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. Clays are composed of hydrated aluminum silicates, such as kaolinite, elite, palygorskite, attapulgite, bentonite, and montmorillonite. Clay exhibits significant volume expansion when mixed with water and significant compression when water is withdrawn.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. The method of installation is A) Drill a hole, at an angle, to a pre-determined depth under the slab – usually no more than 10 feet down. C) Form in rebar into the hole and form an 18” cap on top. C) Fill the hole with concrete after mixed with a curing agent and let the concrete set-up for 7-14 days. KEY POINTS: This pier will carry a 3-10 year warranty on average with a charge to make adjustments up to 100% of the cost of the pier. Since this pier is only drilled to a predetermined depth and at an angle, it’s expected to fail in that time frame if the things that caused the foundation to fail in the first place are not addressed. The soil that is drilled out of the ground will be piled up around the home for the 7-14 days which will cause the foliage in that area to die in most cases.


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 which is used to support non-load bearing areas like patio’s, porches or small enclosed additions. They are less expensive on average and will not cause structural damage when being placed under such small areas that do not have a thick beam. Some structures used footings during original construction to gain depth into the soil.


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 that is used to collect water that migrates under ground. It is not used to collect large amounts of water from a heavy rain fall. French Drains are usually dug down 36-48 inches. Then 1 1/4” river rock is placed at the bottom of the trench and a 4” corrugated pipe is placed over this rock. Once in place, the trench is filled with river rock to approximately 4-6” below grade. The last 4-6” are 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. This is what home and bricks are supported by along the perimeters. The concrete grade beam is, on average, poured 18-20 inches below soil grade and is reinforced with rebar laid inside the concrete for additional support.


GRADING – Grading is the term used to describe the direction water would flow on the soil. Traditionally, you want to have the soil graded away from the house at a rate of 1 inch of drop per foot of grading (often away from the home.)


INTERIOR PIER – When a slab foundation has dropped in an excessive amount and the elevations inside the home must also be brought up to an acceptable level, an interior pier is often used. The pier is placed under a load bearing wall and often under an interior beam support. Once the pier is in place, the hole is filled with dirt and the top is capped with concrete so it is less noticeable.


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 that has had a lift in excess of 2”, a gap is created under the slab. If this gap is not addressed, the concrete will begin to sag until it rests directly over the soil thus filling this gap. If this sagging occurs, excessive cracking will take place and it will have all of the signs of a foundation problem. Mud jacking is a process used to fill these voids and add additional support under the home’s foundation. It is usually a cement / soil mixture and is pumped under pressure underneath the foundation.


NON-OBSTRUCTED PIER – This is a pier that can be placed in the ground without any additional work (i.e. concrete removal, deck removal, etc.)


PIER & BEAM FOUNDATION – A pier & beam foundation is a method of foundation using beams, joists, under-structure supports and often a grade beam. This type of home is raised off of the ground using the grade beam and supports allowing access to plumbing and wiring. It is held straight using beams that run from one end to another at a span of 8-10’ on average. These beams have joists atop them running from one beam to the next. Then on top of the joists is the sub floor which we walk on. The use of this type of foundation requires a lot of wood and 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. A report is done both before and after repairs on slab repairs and only after the repairs are completed on pier & beam repairs. The reports will be taken to test both high pressure and sewage lines to detect leaks.


POSITIVE DRAINAGE – Positive drainage is the expression used to describe the soil laid around the perimeter of the home in a way that water moves away from the house. Minimum grading is a 2” drop over 2’. This prevents water from ponding around the perimeter of house causing migrating water and helps control the moisture content of the soil.


PRESSED PIER – In the early 90’s, an alternate method to repair the home emerged. People wanted a longer-term repair that was less volatile to the elements around it. A pressed pier is a pier that is, on average, 6-8” in width made up of pilings that are 12” in length. This pier is made up of individual pilings that are pre-pressed and pre-formed and is ready to be placed into the ground. These pilings are pressed into the ground using a hydraulic press. The pilings are locked together using either steel shims or a single piece of cable. The piers are pressed to refusal and below the volatile soil. Refusal is either bedrock, hardpan, a very large boulder or when the amount of soil built up under the pier becomes so compressed that it can no longer be pressed any farther due to friction. The average depth of these piers is 12-20 feet in the DFW area. This is the equivalent of placing a foundation on stilts thus making it less vulnerable to the volatile soil around it.


RETAINING WALL – A retaining wall is used to support eroding soil in areas where the ground is volatile. They also help move water away from an affected area with the installation of a French drain at the base of it. These walls are also used to provide additional support to foundations that are built up using fill dirt etc.


ROOT BARRIER – A root barrier is used when a large tree or a group of medium trees are placed too close to a slab foundation. Trees in the DFW area require 50-500 gallons of water per day depending on their size, type and time of year. The roots of these trees will travel under the foundation and will draw moisture from these areas-especially during the hot & dry months. The result is a lack of moisture under the slab in these areas causing the soil to become compressed thus allowing the affected area of the slab to settle-possibly causing a foundation problem. The roots can also find their ways to plumbing sources i.e. bathrooms and kitchens. Once the smallest crack is created in the pipe for whatever reason, the root will then grow into the plumbing for a greater water source. This also causes additional plumbing problems. To prevent this from happening, a trench is dug along the slab of the home, cutting through the roots at the same time. Then a piece of 30” steel is unrolled and placed in the trench to prevent the future growth of these roots back under the house. The trench is then filled back in and all foliage is put back into place.


SETTLING - This term refers to a process or situation where part of a home's foundation has moved below its original elevation. It usually results in interior and exterior cracks in various places throughout the home. It is caused by the home experiencing a loss of mass under the foundation which originally supported it.


SILL PLATE – Sill plate is the term used for the 2x4 or 2x6 piece of wood that is placed along the top of the Perimeter Grade Beam on a pier & beam house. This wood is either pressure treated or oil dipped (much older homes) to prevent moisture from traveling from the concrete grade beam into the joists or beams. When the home is subjected to excessive water in a certain area, the sill plate will deteriorate and become rotten and require replacement. Often times this deteriorated wood will become compressed and cause cracking in the sheetrock of the roof and walls. Replacing the sill plate is tedious but necessary for the longevity of the foundation.


SLAB FOUNDATION – In Texas, slabs are generally cast monotonically with perimeter as well as interior beams that are designed to provide sufficient support for the entire structure as well as to provide stiffness to resist differential soil movement enough to limit cracking in the foundation and finishes. Texas slabs are typically reinforced with conventional reinforcing steel (re-bar) and/or post-tensioned cables that are installed throughout both the slab and beam portions of the foundation. It is supported entirely by surface soils. (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.


SONITUBES – In most of the pier & beam foundations built, the use of poured sonitube piers are used to support the beams that run under the house. They are placed 12-18” under the soil grade and rebar is placed inside of the tubes for additional support. They are far superior and less susceptible to movement than “pad supports” which are stacked concrete blocks placed on an 8” to 18” pad which is usually placed on top of the ground.


SUMP PUMP – A sump pump is used in conjunction with surface drains and French drains when the water that is being moved to a common point is lower than the designated outlet. Sump pumps are automatic and will automatically turn on when enough water has accumulated in its well. The water is then pumped to a designated area (i.e. street or lower spot below the foundation grade.)


SURFACE DRAIN – A surface drain is used to move large amounts of water that collect on top of the ground. In most cases down spouts from rain gutters are also tied into the surface drain to help move water. A 4” pipe is placed underground with collection boxes located at optimal areas which collect surface water and moved away from the affected area. These are the most common type of drain used to correct improper drainage or grading.


TRANSFERABLE WARRANTY – The warranty that is placed on a service or good that stays with the product and only owner of the warranty changes. The transfer usually has a fee charged for administrative expenses.


UPHEAVAL - This term refers to a process or situation where part of a home's foundation has moved above its original elevation. It usually results in interior and exterior cracks in various places throughout the home.


UNDERPINNING - Underpinning is the process of modifying an existing foundation system by extending it to or into subsurface strata that is deeper and more stable than the near surface soil that sup- ports the existing foundation system. This is done to provide vertical support that is not present in the existing design. Methods of underpinning include the construction of footings, stem walls, driven piling or drilled piers.


VENT- POWERED WITH A HYDRO-STAT – Many pier & beam foundations have inadequate ventilation and/or drainage. The result of this is excessive moisture migrating under the home and remaining there. Long term moisture under homes causes rotten wood, upheaval, compressed soil and eventually a sagging foundation. A powered fan can be installed at an existing vent location which draws air out from under the home creating cross-ventilation. This cross ventilation helps in evaporation of moisture under the house in the soil, concrete and wood. The use of a hydrostat allows the fan to only turn on when moisture levels under the house reach pre-determined levels.


VENTILATION – Ventilation and cross ventilation are one of the keys to long-term ownership of a pier & beam foundation. Proper ventilation helps maintain the desired climate in the crawlspace of the home. Texas State Code for ventilation is 1-square foot of ventilation per 150-squre foot of first level pier & beam foundation. So a 1500 square foot house should have a minimum of 10 vents located at optimal locations.


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

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