Structural drying and dehumidification

The four things being balanced

Airflow, humidity, temperature and time, and you cannot fix a shortfall in one by adding more of another indefinitely. Air movers put moving air across wet surfaces, which is what makes water leave the material. Dehumidifiers take that water out of the room air, which is what stops it landing somewhere else in the building — usually a cold surface two rooms away, which is how a badly run dry-out creates a second problem.

Warmth helps, up to a point, because warm air holds more water. And time is what the other three buy you. Adding twice the equipment does not halve the time: past a certain point the material itself is the limit, and the extra machines are just noise on your electricity bill.

Why we will not promise you three days

Most residential water losses dry in three to five days. We will tell you which end we expect yours to land on, and we are right most of the time. But it is a forecast from readings rather than a promise, and the honest reason is that four variables decide it and only two of them are ours.

What the materials are: solid timber holds and releases water slowly, plasterboard quickly, plaster on lath somewhere maddeningly in between. How much they took. How warm the building is and stays. And — the one that ruins schedules — how much of the wet is trapped behind something that has to be opened before it can be dried at all.

So the equipment stays until the readings meet the dry standard. If that is day three, we collect on day three and stop charging for it. If it is day seven, we tell you on day four rather than on day seven, and we tell you why.

What the daily visit actually is

Somebody comes every day the equipment is in. They take readings at the same marked points with the same instrument, record them dated against the reference reading from the unaffected area, check the dehumidifier is actually pulling water and not merely running, reposition air movers as the wet area shrinks, and remove machines that are no longer doing anything.

That log is not paperwork for its own sake. It is the document that decides when we stop, and it is the document an adjuster asks for when they want to know why the equipment was in for six days. A drying job with no daily readings is a drying job with no evidence, and you should be suspicious of one.

Drying in place versus taking it out

Modern drying saves a great deal that used to be demolished on day one, and we would always rather try. Solid hardwood, plaster, structural timber and most masonry are worth drying. Engineered board, MDF, chipboard, most insulation and anything laminated is usually not — it has already swollen and delaminated, and drying it produces a dry version of a ruined material.

The cases where we open up rather than dry through are the ones where air cannot reach the water: a cavity wall, the void under a bath, the space beneath a fitted kitchen, insulation in a floor. Drying around trapped water is how a water job becomes a mould job a fortnight later, and it is the failure this trade commits most often because it looks like restraint at the time.