Foundation Repair Terminology

Causes of foundation problems aren’t always straightforward, and the terminology related to these problems and their repair can be confusing. Dura Pier believes that commercial and residential property owners facing foundation problems should learn as much as possible about the sources of the problems and their solutions. Understanding the terminology can help. Below is a list of the of the common terms you can expect to encounter.

Active Zone: The soil under our homes is made up of various layers. The active zone is the zone of soil that either is contributing to or has the potential to produce heave

Bell Bottom Pier: A drilled pier with an enlarged bottom end designed to increase the load bearing capacity. Typically, two to three times the shaft diameter. Contains rebar of a specified width and length.

Block & Base: A type of foundation whereby treated 4”x6” wooden beams act as the primary members of the foundation and are supported by pre-cast concrete blocks. The blocks serve to elevate the home, creating a crawlspace underneath the home.  Running perpendicular to the beams are wooden floor joists, upon which sits the sub-floor.

Builder Piers: Drilled, often times bell-bottomed, piers installed before the foundation is poured. 

Canopy: The outermost diameter of a tree’s branches. Also known as the “drip line”.

Carbon fiber strips: Lightweight, high strength material used to reinforce concrete slabs and walls affected by bowing, or to tie cracked or separate slabs together.

Certified Foundation Repair Specialist: A designation offered by the National Foundation Repair Association and reserved for those that meet strict requirements of continuing education, successful completion of rigorous examination and commitment to acting in accordance with the highest standards of ethics and honesty.

Clay: A type of soil that which possesses a high capacity for expansion and contraction in relation to its water content.

Concrete piling: A slim column of concrete with steel rebar in its center. The concrete piling is driven into the soil to a predetermined depth and used to support a building’s foundation.

Corner Pop: A common occurrence where a small corner of the concrete slab foundation has cracked or completely popped off.  While not a major foundation problem, these should be properly repaired to prevent water and bugs from entering the home through the cracks. 

Crawl Space: The space under homes which are elevated above the ground with piers or blocks. 

Depth of Refusal: The depth at which a piling cannot be driven any further into the ground. At this point, any additional force applied will cause the structure above the piling to be lifted.

Drilled-in caisson: An open-ended pipe driven into the ground. It is cleaned out and a cavity is drilled into ground below the bottom end of the pipe to receive a steel core. Finally, the cavity and the entire pipe is filled with concrete.

Drilled pier: A concrete pier cast in place in a hole drilled to a pre-determined depth. Includes rebar.

Driving cap: A steel cap placed over a pile to prevent damage during the pile driving process.

Dura Lock™: Dura Pier’s patented foundation repair system that combines the durability of concrete with the strength of steel to ensure the piling is driven straight into the ground and the cylinders aligned for good.

End Bearing Capacity: One of the two factors that make up the load bearing capacity of the pier or piling. The end bearing capacity is a function of surface area of the bottom surface of a pier or piling.  For example, an 8” diameter pile cylinder will have a larger end bearing capacity compared to a 6” diameter cylinder. This capacity varies depending on the exact soil on which it rests. 

Elevations: Measurements taken by an instrument to determine the varying slope of a foundation. Examples of instruments include a simple level or a high-precision hydrostatic altimeter.

Expansion Joint: a spacing in an exterior façade or concrete slab designed to allow for the safe expansion and contraction of building materials, and vibration, or to allow for movement due to ground settlement or seismic activity.

Expansive soil: Soil that expands and contracts due to the presence or absence of water. Clay is an example of expansive soil. Clay has a large capacity to absorb a large volume of water which causes the clay to expand.  When it dries out, the clay contracts.  This pattern repeated over time puts stress on a structure’s foundation.

Exterior: The outermost perimeter of the structure where piers or pilings might be installed. As opposed to the interior of the structure. 

Fill Dirt: Soil added to a construction site to provide the desired level or grade. A structure’s foundation can be impacted by the type of fill dirt used and the degree to which it is compacted prior to construction. 

Floor Joist: For structures with a crawlspace. Wooden members of a structures’ foundationwhich run perpendicular to the thicker wooden beams. Floor joists provide support to the sub-floor which is typically plywood.

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

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 buried in a trench surrounded by rock and designed to capture and divert water away from the structure.  Sometimes a catch basin and discharge pump are required if sufficient natural grade does not exist.

Frost heaving: Soil expansion that results when water in the soil freezes due to the fact water expands when frozen.

Full Tilt: A scenario in which the entire concrete foundation slab tilts. If the ground is exposed to frost or excess moisture, it may shift and expand, leading to the entire concrete slab moving. In cases like these, your walls may crack or bend due to pressure differences.

Grade: The slope of the ground surface.

Grade Beam: The thickest parts of a slab foundation. Made thicker and reinforced with rebar to provide added support to load bearing walls.

Gravity discharge: Uses a natural or man-made slope to move water away from away from a structure’s foundation.

Grouting: The process of injecting a mixture of cement, sand and water to fill voids and increase the load bearing capacity of the soil to help stabilize foundations. Polyurethane injection is a popular grouting alternative.

Gumbo clay: Highly expansive clay soil commonly found in the southern and western United States.

Upward expansion of soil commonly caused by the soil absorbing water. Can lift a structure’s foundation.

Helical pier: A 3” diameter steel pipe with circular steel discs at the bottom of the shaft that are mechanically driven into the ground like a screw to provide support for a new foundation or to adjust an existing foundation. Helical piers are typically 2-3 times the price of a concrete piling.

Interior: The area inside the perimeter of a structure. 

Load Bearing Capacity: The total weight a pier or piling can support.  This is determined by the skin friction which is unique to each soil type applied against the total area of the piling plus the end bearing capacity.

Mini Pile: A pile with a smaller diameter-to-length ratio, typically 2 7/8”.  These piles can be helpful when supporting lighter structures due to the ability to drive these piles to a greater depth.

Moisture barrier:
 A waterproof barrier which prevents moisture in the ground from leaching up through your foundation and into your home. Homes are built with this barrier, but they may degrade over time.

Monolithic Slab: A concrete slab that is poured all at once.  Your front porch might have be a part of your home’s foundation slab in which case it is monolithic.  Or it could be a separate slab that is free to move.  Monolithic does not mean it is of uniform thickness throughout.

Mud Jacking: A process whereby a water, soil & cement, or similar mixture, is pumped beneath the slab, under pressure, to produce a lifting force that literally floats the slab to desired position. Polyurethane foam injection is a popular, cleaner method.

Pier and Beam: A design where perimeter loads are carried on a continuous concrete beam supported by piers. Interior loads are carried by isolated piers in a grid pattern.

 Concrete poured into drilled shafts beneath a structure’s foundation. May be used to stabilize or lift back into place a foundation.  Typically, 12’-20’ deep. Please note the term “piers”, “piles” and “pilings” are often used interchangeable among many people in the industry.

Pile: Deep and narrow wood, steel or concrete structures driven and throughout a structures foundation to stabilize. Please note the term “piers”, “piles” and “pilings” are often used interchangeable among many people in the industry.

Piling: A pile or pier connected to a structure by one or more ties to facilitate lateral support and resist uplift. Please note the term “piers”, “piles” and “pilings” are often used interchangeable among many people in the industry.

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.

Polyurethane Foam Injection:
 A process whereby polyurethane is pumped beneath the slab, under pressure, to produce a lifting force that literally floats the slab to desired position. The polyurethane will be blended with activators that cause it to expand at a desired rate depending on the moisture level in the soil. 

Post Tension Slab: a section of cured concrete, which has tensile forces introduced into the slab after the concrete has been set. These internal forces are provided by tensioning the high-strength steel cables that are placed throughout the slab in a grid pattern. This compresses the concrete.

Rebar: Short for “reinforcing bar”, is a steel bar or steel mesh wire used to add strength to concrete.

Root Barrier: A physical or chemical barrier installed in the ground. A properly placed root barrier will hold back or redirect root growth. Often root barriers are used to keep roots from growing under sidewalks or other infrastructure to avoid costly damage.   

Sewer Clean Out: A plumbing pipe which sticks out of the ground that has a removable cap and is connected to the main sewer line. This provides plumbers access to the sewer line to clear out a blockage or run a camera in the line during the leak detection process. 

Sewer Leak Test: The sewer line under or around your home is plugged and filled with water.  If the water level does not drop, there is no leak.  If the water level drops there is a leak.  This test will either need to be repeated in an isolated manner, or a plumber will run a camera through the line to determine the location of the leak. 

Sewer Line: Typically, a 4” line that carries wastewater from your home to the municipal sewer main or a septic system.  This line is not under pressure.  Newer homes use PVC while older homes were built using Cast Iron, concrete, or ABS (Acrylonitrile Butadiene Styrene). 

Skin Friction: The force between a pile and the surrounding soil.  Different soil types have different levels of friction.  The less friction there is, the deeper a pile can be driven.  The deeper a pile is driven, the more skin friction builds.  Higher skin friction contributes to a higher load bearing capacity.  Therefore, all things being equal, a deeper pile will better support a structure.

Slab: A concrete block supported by the soil beneath its surface.  Concrete slabs make up the vast majority of the foundations for new homes build in areas with expansive clay soils. 

Shims: ¼” steel plates placed between the pile caps and the foundation to provide building support after final leveling.

Sub-Floor: Typically, pressure treated plywood placed on top of floor joists and beams upon which a homes’ flooring is placed. 

Steel pier: Consist of 12” long segments of 2 7/8” diameter steel pipe that can be driven deep into the soil for foundation support.

Sump pump: A devise used to forcibly push water away from one area and towards another. Typically needed when the natural slope is insufficient to move the volume of water that is collecting in an area.

Water table: The level below which the ground is saturated with water.

If you still have any questions, please feel free to call us at 713-721-8888 or 214-699-4784. We’d be happy to answer any questions you might have.

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