There is a moment in every water damage job where somebody says “it feels dry now”, and everything after that moment is decided by whether anybody checked.
If the answer is no, the next time you find out is when the paint blisters, the floor cups, the smell arrives on the first warm week, or a mould remediation quote lands in a room you already paid to repair. That is the same money spent twice, and it is entirely avoidable for the cost of an hour.
The one idea that matters: the dry standard
There is no universal number that means dry.
Building materials sit at different moisture contents depending on their age, their species, the assembly they are in and the season. A subfloor in a century house between the harbour and Hurontario in Collingwood and a subfloor in a fifteen-year-old build on the south edge are two different numbers on an ordinary Tuesday in March, and both are correct.
So drying is not judged against a table. It is judged against the same material, in the same building, in an area that never got wet. That reference is the dry standard for your job, and taking it is the first reading of the whole process — before any equipment goes in.
This is why a competent job starts with somebody walking to a dry room and putting a meter on the wall there. If nobody did that, there is nothing to declare the job finished against.
What a moisture log should contain
A properly run drying job produces this anyway. You should be given it without asking, and asking is free.
| What | Why it is on there |
|---|---|
| Date and time of each visit | Establishes the sequence, and it is what an insurer reads |
| Location of each reading | A number without a location cannot be repeated |
| The instrument used | A pin meter and a pinless meter are not measuring the same thing |
| The dry standard readings | The comparison the whole job is judged against |
| Ambient temperature and humidity | Says whether the equipment had a chance of working |
| Equipment on site that day | This is also the invoice, so it should reconcile |
Two things are worth checking on it. First, that the readings are falling — a flat line for three days means the equipment is not reaching the wet material and something needs to be opened. Second, that the last two days match the dry standard rather than merely being lower than they were.
The instruments, and what each one can honestly say
A pin meter drives two probes into the material and measures resistance between them. It gives a value for that material at that depth at that point. It leaves two small holes, which is why people resist it and why it is the one that settles arguments.
A pinless meter reads a shallow depth without marking the surface. Fast for scanning a wall to find the edge of a wet area, less useful for a number you want to rely on, and it can be fooled by anything conductive behind the surface.
A thermal camera does not detect moisture at all. It detects temperature difference. An evaporating wet area is usually cooler than its surroundings, so wet patches often show — and so do missing insulation, draughts, cold water lines and the shadow of a stud. It is an excellent tool for deciding where to put a meter and it is not evidence on its own.
A hygrometer reads the room air rather than the material. It tells you whether the dehumidification is winning, which is a different question from whether the wall is dry.
If somebody shows you a thermal image and nothing else, ask what the meter said at the same spot.
Where it goes wrong in this region specifically
Cold saturated air. Environment Canada normals at the nearest reporting station put the Collingwood area near 996 mm of total precipitation a year across roughly 92 days that cross freezing and come back. A February drying job with the outside air cold and saturated is a closed-system problem — ventilating makes it worse, and it needs more dehumidification than the same job in May.
Buildings held at low heat. A chalet in The Blue Mountains at 12°C dries slowly because evaporation is slow, and equipment brought in without restoring heat first is running at a fraction of its rated capacity.
Old assemblies on a damp valley floor. In Clarksburg and along the Beaver River the baseline humidity in an old basement is genuinely higher than on the escarpment top a few kilometres away. A reading that would be alarming in a new build can be normal there, which is exactly the situation the dry standard exists to handle.
When to buy a second opinion
Three moments, and one of them is worth more than the other two.
Before the walls close is the one that matters. Once drywall, flooring and trim go back over a wet assembly, nobody knows anything until the finish fails. An independent moisture inspection at that point costs a few hundred dollars against a repair you have already paid for once.
The other two are when a scope looks disproportionate in either direction, and before a sale or a purchase where a ceiling carries a stain of unknown age. In both cases whoever holds the readings holds the position, and usually neither side has any.
The sentence to look for
A final report should contain a version of this: the affected materials have matched the dry standard taken from unaffected material in the same building across two consecutive days, and the equipment has been removed.
If the report does not say that, the job did not end on a measurement. It ended on a date, and dates are chosen by whoever is paying for the equipment.