Basement and foundation glossary

Backfill

The soil replaced against a foundation wall after construction or excavation. Poorly compacted backfill settles over time, which is a common reason exterior flatwork and grading pitch back toward a house.

Battery backup sump pump

A secondary pump powered by a battery during a power outage or primary-pump problem. Runtime depends on the battery, pump demand and system design.

Bowing wall

A foundation wall that curves or moves inward, often measured at the point of greatest displacement. Repair is structural, not simply cosmetic crack sealing.

Bulkhead

An exterior basement entrance with a hatch, frame and stairwell. Leaks commonly originate at the frame-to-foundation joint or a blocked stairwell drain rather than at the door itself.

Capillary action

The movement of water upward through porous material such as masonry or soil against gravity. It is one route by which a wall or slab can be damp without any visible leak.

Carbon-fiber reinforcement

Straps or fabric bonded to a suitable wall to resist additional inward movement. The wall condition and attachment design determine whether it is appropriate.

Check valve

A valve on a sump discharge that limits water from flowing back into the pit after the pump stops.

Clay bowl effect

The tendency of backfilled soil around a foundation to stay looser and more absorbent than the undisturbed ground beyond it, so the excavation behaves like a bowl holding water against the wall. It is one reason water collects at a foundation even where the wider site drains well.

Cold joint

The seam where fresh concrete was placed against concrete that had already set, such as between a footing and a wall. Cold joints are a common water path because the two pours never fully bonded.

Combustion appliance

A furnace, boiler, water heater or stove that burns fuel. Their presence affects how a basement or crawlspace may be sealed or depressurized, and is a safety consideration in encapsulation work.

Condensation

Moisture forming on a surface colder than the dew point of the surrounding air. It is produced by indoor humidity rather than water entering from outside, and it is corrected differently from seepage.

Cove joint

The seam where a basement wall meets the floor slab. Water can become visible there when it reaches the footing or area below the slab.

Crawlspace encapsulation

A sealed ground and wall vapor-control system, usually coordinated with drainage, air sealing, insulation and humidity control.

Dew point

The temperature at which air becomes saturated and moisture condenses. Basement walls and cold pipes below the dew point of summer air will sweat regardless of how well the foundation is waterproofed.

Differential settlement

Settlement that occurs unevenly across a structure, so one part drops relative to another. It is what produces racked door openings, diagonal cracks and sloping floors, as opposed to uniform settlement that moves everything together.

Discharge line

The pipe carrying water from a sump pump to its outlet. Length, lift, freeze protection and where it terminates matter as much as the pump itself.

Downspout extension

Pipe carrying roof water from the base of a downspout to a point away from the foundation. One of the least expensive and most frequently missing corrections for basement water.

Drain tile

Perforated drainage pipe placed beside a footing or below a slab to collect water. The pipe must have a working outlet or sump.

Dry well

A buried, stone-filled or chambered pit that receives drainage water and lets it soak into the surrounding soil. Used where no gravity outlet to daylight is available.

Efflorescence

A white mineral deposit left when water moves through masonry and evaporates. It is evidence of moisture movement, not a mold species.

Egress well

The window well serving an egress window, sized for escape and typically requiring a ladder or steps at depth, a drain and an openable cover.

Egress window

A window opening designed to meet code requirements for emergency escape and rescue where those rules apply.

Encapsulation liner

A durable membrane sealed over a crawlspace floor and often extended up walls or around piers to control ground moisture.

Exterior waterproofing

Work performed from outside the foundation that may include excavation, wall repair, membrane, drainage board, footing drainage and backfill.

Footing

The widened structural base that transfers a foundation wall or column load to supporting soil.

Footing drain

A drain installed beside the footing to collect subsurface water and carry it to a gravity outlet or sump.

Foundation anchor

A structural system that connects a wall to stable soil or another designed resistance point to limit additional movement.

Foundation pier

A deep-support element used to transfer a settling foundation load to stronger soil or bearing material below.

Freeze-thaw cycle

Repeated freezing and thawing of water held in masonry, concrete or soil. The expansion on freezing breaks down mortar, spalls concrete surfaces and moves shallow footings, and it is a dominant weathering mechanism in the Vermont climate.

French drain

A gravel-and-pipe drainage trench that intercepts or carries water. Its location, fabric, pipe, slope and outlet determine what it can do.

Frost depth

The depth to which ground freezes in a given climate. Footings placed above it are subject to frost movement, which is why shallow porch piers and steps move more than house footings.

Grade

The slope of the ground surface. Positive grade falls away from a building; grade that has settled toward the wall delivers surface water directly to the foundation.

Header

A structural member spanning an opening to carry the load above it. Required when a section of foundation wall is removed, such as for an egress window.

Heaving

Upward movement of a slab or footing, usually caused by freezing in saturated material. It produces raised cracks rather than the dropped ones associated with settlement.

Hydrostatic pressure

Pressure created by water in soil or below a slab. It can drive seepage through joints, cracks and porous materials.

Hygrometer

An inexpensive instrument measuring relative humidity. Using one removes the guesswork from judging whether a basement has a humidity problem or a bulk-water problem.

Interior perimeter drainage

A drainage channel installed along the inside edge of a basement floor to collect water and direct it to a sump or gravity outlet.

Joist

A horizontal framing member supporting a floor. Joist ends bearing in damp masonry pockets are a frequent starting point for decay in older basements.

Lally column

A steel post, often concrete-filled, used to support a beam in a basement. Where it bears on a thin slab without an adequate footing beneath, it can settle and take the floor above with it.

Lateral pressure

Sideways pressure on a foundation wall from soil, water, frost or other loads.

Masonry repointing

Removal and replacement of deteriorated mortar between stone, brick or block. It repairs joints but does not by itself correct every drainage or movement problem.

Mudjacking

A method of lifting a settled slab by pumping material beneath it to fill the void and raise the concrete. Also referred to as slab jacking or concrete leveling.

Negative-side coating

A coating applied to the inside face of a wall while water pressure originates on the opposite side. Suitability depends on the wall and water condition.

Parging

A thin coat of mortar applied to a masonry wall surface. Cosmetic over unstable or loose masonry; useful as part of a repair where the wall beneath is sound.

Perched water table

Groundwater held above the regional water table by a less permeable layer of soil. It can produce seasonal basement water on a site whose overall water table is deep.

Positive-side waterproofing

A waterproofing layer installed on the side of an assembly first exposed to water, such as the exterior face of a foundation wall.

Radon mitigation

A system designed to reduce indoor radon, commonly by drawing soil gas from below a slab or membrane and exhausting it outdoors. Encapsulation alone is not automatically mitigation.

Relative humidity

The amount of moisture in air relative to what that air can hold at its temperature. Measuring it with a hygrometer is more reliable than judging basement dampness by feel.

Rim joist

The framing area around the perimeter of a floor system above a basement or crawlspace. Air leakage and condensation can occur there.

Sacrificial anode

A metal component in some water heaters and tanks that corrodes in place of the vessel. Relevant in a basement because a failed tank is a common source of water mistaken for foundation seepage.

Sill plate

The horizontal framing member resting on top of the foundation wall and connecting the foundation to the structure above.

Sistering

Fastening new framing alongside an existing damaged member to restore capacity, commonly used where a joist end has decayed but the rest of the member is sound.

Spalling

Flaking or breaking away of a concrete or masonry surface, usually from freeze-thaw action or moisture and salt exposure. It indicates the surface is deteriorating rather than simply stained.

Stair-step crack

A crack following the mortar joints of a block or brick wall in a stepped pattern. It commonly indicates differential movement rather than simple shrinkage.

Sump basin

The pit or sealed container that receives drainage water before a sump pump removes it.

Sump discharge

The pipe route that carries pumped water outside. It must terminate safely and remain functional during freezing conditions.

Underpinning

Extending or strengthening an existing foundation downward to reach more competent support, typically used where settlement is ongoing.

Vapor barrier

A material used to limit water-vapor movement. It does not replace drainage where liquid water is present.

Wall brace

A steel or engineered structural member installed against a foundation wall to resist additional inward movement.

Wall-floor joint

Another name for the cove joint where the basement wall and floor slab meet.

Water table

The level below which the ground is saturated. It rises seasonally, which is why some basements are dry most of the year and wet each spring.

Weep hole

A small opening allowing trapped water to drain out of a wall assembly or block core rather than accumulating inside it.

Wicking

Movement of moisture through a porous material by capillary action, such as a concrete wall drawing water upward from a wet footing. It produces damp masonry without any visible crack or leak.

These definitions explain common terms; they do not diagnose a property or replace a written repair design. Request an on-site inspection.