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Foundation Repair Glossary of Terms

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1. Glossary Of Foundation Repair Terminology

Ever heard a word or phrase used by a foundation repair professional and had no idea what they are talking about? You are not alone. The terminology used to describe foundation problems and repair techniques can be confusing. Understanding some basic terms can give you more confidence when hiring a professional to work on your home or business. Review the foundation repair terminology glossary below before investing in repairs for your structure.

Glossary Of Foundation Repair Terminology

Active Zone/Layer: the layer of soil that extends from the surface to the deepest depth of seasonal moisture variation in soil. Soil movement and instability usually occurs in the active zone/layer of soil.

Beam: In a pier and beam home, beam refers to a wooden support member consisting of dimensional lumber pieces sandwiched together to support floor joists and the above structure. In slab foundations, concrete beam refers to the thickest part of the slab, usually found around the perimeter of the foundation and reinforced with tension cables or rebar. “Beam” may also refer to a metal I-beam, part of the structural support of the home or business.

Bedrock: The solid layer of rock/earth beneath the active layer and loose deposits that requires either blasting or jackhammering for excavation. The bedrock is suitable for supporting a structure.

Below Grade: Below the ground level.

Bowing Wall: Any wall – foundation/basement wall, exterior wall, interior wall, etc. – that is bent or curved due to stress from expansive soil, structural failure, or other elements.

California Slab: A slab with wood flooring on top of it. The flooring is usually laid on top of runners, creating a hollow sound that leads one to believe it is a pier and beam foundation.

Carbon Fiber: A strong and lightweight man-made material made of small fibers of carbon that can be woven into fabric or melted down and molded. Carbon fiber strips and staples are often used to fix cracks, strengthen bowing walls, and support failing foundation.

Clay: A fine-grained naturally occurring material that is often found in soil. Because it traps water in its molecules, clay particles expand when they get wet and shrinks when it dries out.

Collapsible Soil: Soil that is susceptible to erosion, reduction, or void formation when water is added.

Concrete: a hard material made of sand, rocks, cement, and water that is often used in foundations. Other additives may be added to concrete, but some may weaken the concrete. Too much sand, too little cement, and too much or too little water will also weaken the concrete.

Concrete Pier: Long, slender cylinders made of concrete and used to support foundations. Some Concrete piers are poured on site directly into the ground, while some are pre-cast and pressed or driven into the ground.

Crawl Space: The area under a structure such as a house with a pier and foundation. Most crawl spaces need to be 18″-24″ high, leaving enough room to crawl underneath.

Consolidation: Compaction of the soil usually resulting from gradual water loss, which causes the soil to shrink and pack together.

Deflection: The amount of bending and bowing from a heavy load that a foundation may withstand without total failure.

Differential Settlement: Uneven settlement. This happens when different parts of the foundation and structure are sinking at different rates.

Elevation: The height of various parts of your foundation. The central spot of the elevation is the level position – any higher or lower points have different elevations.

Epoxy Crack Injection: A repair method used to seal cracks. With this method, cracks in concrete are “glued” together using an epoxy grout material that is injected into the crack and seals the two faces together.

Expansive Soil: Any kind of soil, often clay soil, that contracts when water is removed and expands when water is added. This soil often contributes to foundation shifting, heaving, and movement.

Fill: Soil that is added to an area to fill in, level, or grade that area. Sometimes gravel is used as fill instead of soil.

Floating Slab: A concrete slab, normally about 4″ thick, inside the foundation wall or footing but not attached to it. These slabs are typically poured on grade and do not have piers under them. Floating slabs are commonly used in garages and most contain little to no reinforcement.

Foundation: The part of the structure that is in contact with the ground and provides support for the rest of the structure. Foundations do this by transmitting the load of the structure to the ground below.

Footing: A thick, steel-supported concrete slab poured around the edges of the foundation. The footing helps to spread out the vertical load of the foundation evenly. These are installed below grade.

Free Water: Water that can be taken on or lost without a change in the soil volume occurring.

Frost Heaving: Expansion that occurs when the water inside soil freezes, increasing the total volume of the soil up to 25%. This can contribute to foundation movement or heaving.

Grade: The level of the ground surface and the rise of fall per a given distance. Used to measure the slope of the ground around your home and foundation.

Grouting: A method in which material is injected to permeate soil or repair cracks in concrete. When grouting is used in the soil underneath a foundation, it’s purpose is to fill underground voids to lift sinking slabs and level concrete.

Hairline Crack: A very fine crack in concrete, drywall, brick, or any other material that makes up a home or commercial structure. Normally, hairline cracks are not the result of foundation failure.

Helical Piers: Steel devices used to support sinking foundations. These devices consist of long, thin cylindrical steel shafts that are threaded and look like part of a giant screw. The shafts are driven into the ground vertically and connected until the pier reaches a supportive layer of soil and rock below the active layer. The pier is used as a support for the structure, which is raised hydraulically before resting on the pier.

Horizontal Crack: a crack that goes from one end of the wall or floor to the other and runs parallel to the floor or ceiling. These are often serious and are often indicators of foundation settlement.

Hydrostatic Pressure: Pressure in the ground due to water in the soil. The more water the soil absorbs, the more this pressure can build up and compromise the structural integrity of a foundation.

Interior Floors: Floors inside the house, normally supported by beams and posts in the crawlspace or basement of the home.

Jacking: The process of lifting up a structure or slab by driving force on a pier with jacks. This process is used in underpinning to install piers under structures.

Live Load: Any additional weight to a structure added by people, furniture, snow, ice, or water. Water is a particularly dangerous live load.

Load Bearing Capacity: The maximum amount of weight that a foundation can sustain without foundation failure. Any weight over the load bearing capacity may cause the soil beneath the structure to shift, leading to foundation failure or damage.

Masonry Block Wall: Any wall consisting of bricks or concrete blocks. These walls are usually easier to repair than poured concrete walls.

Moisture Content: The amount of moisture in the soil that surrounds your foundation and home. The higher the moisture content, the more the soil will expand.

On Grade: At ground level.

Osmosis: The process by which water transfers through semipermeable material. Any increased pressure resulting from the diffusion of water is called osmotic pressure.

Permafrost: A condition in which the subsoil of the ground stays continuously frozen year-round.

Pier and Beam: This is a kind of foundation construction usually used in residential buildings. Pier and beam homes are raised off of the ground and have a crawlspace under them. The crawlspace, normally at least 18″ high, allows access to the underside of the house, where utilities are located. These kinds of homes usually contain wooden floors.

Check out more about – Buying A House With Foundation Issues.

Polyurethane Foam Injection: This is a method used to lift concrete slabs and slab foundations by injecting expansive polyurethane foam under the concrete. The two-part urethane chemical expands into a foam when mixed. This mixture is injected through small holes under the foundation to fill in underground voids that have caused settlement. As it expands, it fills voids, lifting the foundation and compacting nearby soil to prevent further settlement.

Poured Basement Walls: Standard slab foundation walls. These walls often suffer from cracks due to hydrostatic pressure.

Push Piers: Push piers, also known as resistance piers, resistance piles, push piles, steel piers, steel push piers, or steel push piles, are part of a two-step system that lifts settled foundations. The piers resemble giant steel rods and are driven vertically into the ground until they anchor in stable soils deep underground. The piers are attached to the foundation with a bracket and the foundation is lifted hydraulically while supported by the piers. Once the foundation is lifted, the piers remain underneath to support it and prevent future foundation problems.

Resistance Piers: See above definition.

Screw Jacks: This floor leveling and crawl space repair solution consists of two steel tubes, one inside of the other. The inside tube is threaded like a screw and can be adjusted using a wing nut. This changes the height of the screw jack, allowing it to support and lift the above foundation of the home as a remedy for settled foundations.

Settlement: Sinking of the building’s concrete foundation. Settlement occurs naturally as the soil compacts over time but can occur unevenly if the soil was improperly compacted, or if other phenomena, such as erosion, soil shifting, or hydrostatic pressure occur. An uneven settlement is dangerous and can result in several structural problems throughout the building.

Skin Friction: This is the resistance of the soil around your pier to the downward motion of the pier during installation.

Slab: Concrete that is wholly supported by the surface soil underneath it. Slab foundations often have concrete beams supporting them as well. Slabs are also used for other purposes, such as driveways, sidewalks, patios, pool decks, garage floors, warehouse floors, etc.

Soil: Soil is any loose material of the earth’s crust in various proportions. Soil usually contains water, air, and solid particles formed by fragmented rocks.

Soil Stabilization: Any process by which natural properties of the soil are improved, making the soil into a more solid base for construction.

Soil Compaction: The process by which the particles that make up soil are pressed together so firmly that they have few pockets of air between them. Soil compaction is a necessary step before foundation installation, and poor compaction of the soil might lead to foundation settlement and structural issues.

Stair step Crack: Stair-step shaped cracks in the foundation, wall, or basement wall of a building. These cracks usually occur in brick, masonry, or block homes along the grout lines. If they are wider than 1/8 inch, they may be a sign of a foundation problem. However, they might also be due to normal foundation settlement.

Stress: The force at a point within the soil mass that exerts pressure from the weight of the soil above the point plus any pressure exerted on the soil by the structure.

Structural Integrity: This term describes how structurally sound the foundation and entire building are and whether the foundation can sustain the weight of the building.

Transpiration: The removal of moisture from the soil by nearby tree roots and other plants.

Underground Voids: These are gaps or holes in the ground that form due to soil settlement or erosion. If voids form under the foundation of a building, the building will lack proper support and may settle unevenly, resulting in structural problems and foundation failure.

Underpinning: The foundation repair process by which steel piers (such as helical piers or push piers) are installed under the foundation to stabilize the concrete and lift the sinking structure. In the underpinning process, the piers are driven point-first into the ground (helical piers are screwed into the ground) until they anchor in stable soils beneath the active soil level. The piers are attached to the foundation with a bracket and hydraulically lifted to solve settlement issues .

Upheaval: Lifting of the foundation due to pressure from shifting soil or varying soil water content under the foundation. This often occurs when the soil freezes and water in the soil expands, pushing the foundation upwards.

Vertical Crack: Any crack in a foundation or wall that runs vertically. These cracks are usually signs of foundation settlement.

Water Table: The level in the soil beneath which the ground is saturated with water.

Wind Load: Any pressure on the structure caused by wind or weather.

Steve Egloff

Steve Egloff

Founder of Bay Area Underpinning

Steve is the Founder of Bay Area Underpinning, a foundation repair company serving the San Fransisco Bay Area, California. Bay Area Underpinning was founded in 2005 with the goal of providing a cost-effective, engineered solution to foundation settlement problems with an emphasis on educating customers to make them feel comfortable with the various methods of foundation repair.

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