Gravity is only one pathway
Water follows gravity, but it also spreads by capillary action, flows along framing and membranes, travels through penetrations, and can wick upward in porous materials.
A source on one side of a wall can wet the opposite room without leaving a direct surface trail.
Layered floors hide lateral travel
Floating flooring, underlayment, resilient finishes, membranes and slab interfaces can move water far beyond the original spill.
Floor transitions, cabinets and perimeter walls are useful investigation points because water can collect or change direction there.
Walls can distribute water vertically and horizontally
Bottom plates, tracks, insulation, gypsum cores and paper facings create different paths. Plumbing and electrical penetrations can connect otherwise separate cavities.
Multi-level losses should be mapped on every affected level rather than inferred from the source floor.
Moisture mapping should follow construction
Build the map around wall lines, joists, beams, floor transitions, chases and penetrations. Construction geometry often explains irregular readings better than a simple circular boundary around the source.
Recheck edge locations during monitoring because the apparent boundary can change as concealed moisture redistributes.
Use this guide with field evidence
This guide explains the decision factors specific to how water migrates through walls and floors. A site-specific conclusion still depends on the actual assembly, source condition, access, measurements and changes observed during the project.
For how water migrates through walls and floors, use this page as the focused reference. Return to Structural Drying Intelligence to place it inside the larger drying decision sequence.