BASEMENTATLAS · Problem guide

Cracks or movement

Cracks or movement. Basement underpinning. Start by documenting existing foundation depth, load-bearing support and stability and crack width and pattern. The

Updated 2026-08-30

Ask about this problem Underpinning & foundation strengthening

Short answer

Start by clarifying Do not assume foundation depth. Confirm it from drawings, trial pits or professional investigation before lowering the floor. and Identify load-bearing walls, columns, foundations and temporary support needs before removing soil, masonry or structural material.. The same symptom can have different mechanisms, so document the cause before choosing a solution.

BASEMENT ATLAS

Sources and evidence

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Source types stay separate: technical and authority-adjacent sources support rules and risk topics, while project sources document practical experience.

2 technical/authority sourcesUpdated 2026-08-30

BASEMENTATLAS · Assessment

Cracks or movement

Foundation work is controlled by load paths and sequence. Existing footing depth, soil and groundwater conditions, crack patterns and the size of each working section can change what is safe to excavate or underpin.

1Identify load-bearing walls, columns, foundations and temporary support needs before removing soil, masonry or structural material.2Photograph with a scale, mark the ends, record width and date, and monitor whether the crack changes before choosing a repair method.3Do not assume foundation depth. Confirm it from drawings, trial pits or professional investigation before lowering the floor.

BASEMENTATLAS · Assessment

Assessment: Cracks or movement

Basement underpinning

Basement underpinning. Start by documenting existing foundation depth, load-bearing support and stability and crack width and pattern. The purpose is to understand the building condition and constraints before choosing products, finishes or a work sequence.

Cracks in basement walls

Cracks in basement walls. Start by documenting crack width and pattern, load-bearing support and stability and changes after rain. The purpose is to understand the building condition and constraints before choosing products, finishes or a work sequence.

Foundation settlement around a basement

Foundation settlement around a basement. Start by documenting crack width and pattern, load-bearing support and stability and existing foundation depth. The purpose is to understand the building condition and constraints before choosing products, finishes or a work sequence.

Monitoring basement cracks

Monitoring basement cracks. Start by documenting crack width and pattern, changes after rain and load-bearing support and stability. The purpose is to understand the building condition and constraints before choosing products, finishes or a work sequence.

What to check next

existing foundation depth

The relationship between planned excavation and existing foundation depth governs whether underpinning, staged excavation or a different floor solution is required.

CheckDo not assume foundation depth. Confirm it from drawings, trial pits or professional investigation before lowering the floor.

load-bearing support and stability

Excavation, wall openings, crack repair and floor lowering can change load paths. Cosmetic repair is unsafe if movement or loss of support is still active.

CheckIdentify load-bearing walls, columns, foundations and temporary support needs before removing soil, masonry or structural material.

crack width and pattern

Direction, width, location and change over time are more informative than the presence of a crack alone. Different patterns can point to shrinkage, settlement or structural movement.

CheckPhotograph with a scale, mark the ends, record width and date, and monitor whether the crack changes before choosing a repair method.

future inspection and maintenance

Drainage, pumps, ventilation units, grilles, filters and seals lose performance if inspection and maintenance are neglected.

CheckFind service history, clean or inspect accessible components and distinguish a maintenance failure from an undersized or incorrectly designed system.

changes after rain

A change after rainfall points toward rainwater, surface drainage, wall penetration or drainage capacity rather than a purely indoor humidity problem.

CheckCompare the same area before rain, during prolonged rain and 12–24 hours afterwards. Also photograph gutters, downpipes, paving and ground slope outside.

outside ground level

High ground, paving or soil against the wall changes how much moisture reaches the basement and can bypass otherwise sound internal finishes.

CheckMeasure or photograph the outside level relative to the basement floor and window sills, and note whether surfaces slope toward or away from the building.

pipe and cable penetrations

Pipes, cables, wall ties, old openings and service penetrations are common local weak points for water, air leakage and radon.

CheckInspect each penetration individually, including the outside where possible, and document sealant, sleeves and cracks around it.

existing and planned floor build-up

The layers below a basement floor determine insulation, capillary break, radon control, drying and how water can move at the slab edge.

CheckUse drawings, visible edges, previous work photos or a controlled opening to establish the actual build-up before specifying a new surface or floor.