How water gets into lower levels
Common causes include sump pump failure or power loss during storms, window well flooding, hydrostatic pressure pushing groundwater through foundation cracks, water heater failures, and floor drain backups.
Crawl space moisture
Standing water and high humidity in a crawl space can soak insulation and raise moisture levels in the floor framing above. Cleanup usually involves pumping, removing wet insulation, and drying with dehumidifiers sized for the space.
Finished basements
Carpet, pad, drywall and baseboards in finished basements absorb water quickly. A contractor will measure how high moisture wicked up the walls before deciding what to remove.
Sewage in the basement
If the water came up through a floor drain or toilet, it may be sewage. That is handled as a biohazard cleanup; see sewage cleanup below and mention the source on the call.
Questions
Can the contractor waterproof my basement?
Waterproofing and foundation work are separate trades. Restoration contractors focus on removing water and drying the space.
Who decides what gets removed?
The independent contractor decides scope after taking moisture readings, and discusses it with you before work proceeds.