Dehumidifiers near you

Approved Document F frames moisture as a performance criterion rather than a comfort preference: there should be no visible mould on the inner surfaces of the external walls of a properly heated dwelling with typical moisture generation, and because mould grows whether or not anyone is at home, the humidity criterion is to be met at all times regardless of occupancy.

It then gives the measurable version. For all dwellings, new and existing, the moisture criteria are likely to be met if during the colder months the moving average surface water activity of the internal surfaces of external walls stays below 0.75 over a month, 0.85 over a week and 0.95 over a day. For new dwellings it converts that into room relative humidity: below 65 per cent as a monthly moving average, 75 per cent weekly and 85 per cent daily. The important word is surface. It is the temperature of the wall, not the reading in the middle of the room, that decides whether mould grows.

That is why a dehumidifier alone is an incomplete answer even for genuine condensation. Lowering the humidity of the air helps, but so does raising the surface temperature of the cold wall, through insulation, heating or simply pulling the furniture off it. The guidance on damp and mould makes the same point from the other direction when it says homes that are insufficiently insulated and heated are more prone to the build-up of moisture and condensation on the inside of external walls and windows.

Drying after water damage is a different job from managing winter condensation, and the equipment reflects that. A contractor will normally combine dehumidification with air movement to lift moisture off surfaces, take readings from the fabric rather than from the air, and keep going until the structure reaches an agreed target rather than until the room feels dry. Plaster, screed and timber hold water long after the surface is dry to the touch, which is why premature redecoration is the commonest expensive mistake after a leak.

Two decisions matter early. First, the source has to be stopped and confirmed stopped; running driers against an ongoing leak is pouring money into the air. Second, if the water was contaminated — a drain, a sewer, a flood from outside — drying is not the whole answer and the affected materials may need removing rather than drying, which is a conversation to have before equipment is hired.

Where an insurer is involved, ask who is instructing the drying contractor and who holds the moisture readings, because those records are what determine when the property is signed off as dry and reinstatement can start. Keep your own note of dates and readings even when someone else is managing it.

A domestic dehumidifier is bought rather than quoted for. Where money is at stake is the work around it: an inspection to establish which of the four causes of damp you actually have, remedial work to a wall, roof or floor, improved extraction or heating, or a managed drying programme after a leak. Those quotations move with the number of rooms involved, whether opening up is needed to see the defect, how long drying equipment is on site and metered, whether contaminated water is involved, and how much reinstatement follows the drying.

LokalMatch connects you to those trades and does nothing more. Describe the problem once with your postcode — where the damp is, when it appears and what has changed — and damp specialists, surveyors and drying contractors covering your area respond. Homeowners pay nothing to use LokalMatch, and pros pay for the requests they receive. LokalMatch does not carry out any work, does not set any prices and does not vet, rank or recommend the firms that reply, so comparing what each proposes to investigate before quoting is worth doing carefully.