Structural drying is the part of a water loss that decides how much of the building survives, and it is the part householders can least easily judge, because a wall that feels dry can hold enough moisture to grow mould for weeks. The discipline exists to replace the judgement of a hand on a surface with a measurement taken at the same marked point every day, and a documented downward trend is the actual deliverable.
The water damage assessment, which comes first
Before any equipment is set, the loss is measured. Where did the water come from, what category is it, which rooms and which materials are affected, and how far has it travelled beyond the visible edge. A water damage evaluation establishes those and produces a plan: what is coming out, what is being dried in place, and what the target reading is for each material. Skipping this and simply filling a room with fans is how buildings get dried on the surface and left wet in the cavity.
Moisture mapping
Moisture mapping is drawing the wet footprint rather than guessing at it. Non invasive meters sweep the area to find where readings rise, pin meters confirm depth at specific points, and thermal imaging shows evaporative cooling where moisture sits behind a surface, which is how water in a cavity is found without opening it. The map is marked on a plan with the readings and the date, and the same points are re read each day. It is also the document that later justifies why a particular wall was opened.
Drying out water damage: how it is actually done
Three things at once. Extraction removes bulk water, because removing a litre mechanically is vastly cheaper than evaporating it. Air movement across wet surfaces breaks the saturated boundary layer so evaporation continues. Dehumidification removes the resulting vapour from the air, otherwise the room simply reaches equilibrium and stops. Where a cavity or an assembly cannot be reached, targeted systems inject air into wall cavities, under floors or beneath hardwood. Equipment counts follow the volume and the material, not habit.
Structural cleaning, and knowing when it is finished
On a contaminated loss the structure is cleaned before it is dried, because drying first fixes the contamination in place. Drying finishes when the affected materials reach the same moisture content as comparable unaffected materials in the same building, not on a fixed number of days and not when the surface feels right. That is the number to ask for, daily, in writing. A contractor who cannot produce a drying log with marked points and dates has not dried a building, they have run fans in it.
Questions people ask about structural drying
What is structural drying?
Drying the building assembly itself, walls, floors, subfloors and cavities, to a measured moisture content using extraction, air movement and dehumidification, with daily readings at marked points.
What is moisture mapping?
Drawing the wet footprint on a plan using meters and thermal imaging, so the affected area is known rather than guessed, and so the same points can be re read each day to show progress.
How long should drying water damage take?
It is judged by readings, not days. Typical losses run several days; a saturated assembly takes longer. The question to ask is what the target reading is and how today's compares to yesterday's.
How do I know the building is actually dry?
The affected materials read the same as comparable unaffected materials in the same building. Ask for the drying log with marked points and dates rather than for an opinion.