Your essential guide to drying rooms and buildings after a flood disaster.

The rain lashes down and drains block with fallen leaves and silt. The flood waters rise and search for new destinations. Houses, businesses, shops, offices, schools – the flood water does not discriminate between building types, only what ‘level’ they are at. Although these days flooding can arise at any time of year it is still a particular problem in autumn. Buildings affected can be anything from a bit damp to massively damaged by flood water. Here we provide our top tips for drying outbuildings and rooms affected by flooding. These top tips are as useful for drying up after a burst pipe, or bath overflow as they are for a rainwater flood, and should help you get dry in quick time.

1. If insured, discuss your claim and drying requirements with your insurer. They may hire a contractor to do the drying for you, in which case you can concentrate your attention on saving your contents and making sure that those you are responsible for are accommodated somewhere else. If it is a small drying job, perhaps one that is uninsured, or one that is not worth claiming for then the next 9 top tips are good to go, so long as you can establish that it is safe to do so by first consulting an electrician and perhaps a plumber.

2. Whats wet? No, it’s not a stupid question but the answer will affect how you dry the building and what equipment you use.

Say you have a traditional type constructed building with drywall and concrete floors, complete with wet carpets, then what you are looking at is potentially using a wet vac (to suck up any remaining flood water from your carpet), a carpet dryer fan to blow air under the carpet, dehumidifier and a radiant heater.

If you have a modern solid floor with tiles, timber or laminate flooring, then the chances are that it has been laid with an insulation layer which is saturated and needs to be dried before it can again be an effective insulating layer. For this, you will need a restorative drying unit (to suck water out from the insulation layer under the floor), a dehumidifier and a radiant heater.

3. Use as big a dehumidifier as you can afford. Basically, a little domestic plastic cased machine will not be up to it. You will need a big mobile dehumidifier – consider 30 ltr/day extraction rate as the bare minimum for drying a flood-damaged small room. Bigger is better and quicker. More than one room to dry? Then consider using extra dehumidifiers.

4. When using a dehumidifier make sure to minimise air ingress into the building. Close all doors and windows and trickle vents (if you have them). The idea here is that by keeping the building air sealed, that the air in the building can be made as dry as possible with the dehumidifier, without giving it the extra burden of drying extra air from outside.

5. Ensure the dehumidifier is positioned so that it can treat the air without any obstructions. Placement in the middle of the room is best. If you have a large room and a number of dehumidifiers working simultaneously, spread them evenly in the room and away from walls.

6. Use portable radiant heaters for heating up surfaces, such as plasterwork. Warm walls will evaporate water far quicker than cold walls. Either use conventional portable radiant heaters or use radiant masonry drying panels. Don’t put them too close to the wall otherwise, you will get a hot spot, but do place the distance away so that a greater area is gently warmed.

7. Add extra heat. Radiant heaters when used will also in time warm up the air in the building, but it is still cold put in electric space heaters in to raise the air temperature. Don’t use direct fired oil or gas heaters for this purpose as they will deplete the oxygen in the building. If you need more heating power, beyond what the mains supply to the building can safely provide via electric heaters, then use indirect fired oil or gas heating, with the heater located outside and warm air ducted in, ideally on a recirculation system so that heat is not wasted to the outside. Ideally, the building air temperature needs to get to at least 20°C. The warmer the air is the more moisture it can hold, the more water will evaporate from surfaces, and the more efficiently the dehumidifier(s) will work.

8. Work out what happens with the condensate collected by the dehumidifier. If it collects in a tank, remember to frequently empty the tank. If you do not do this the dehumidifier will stop to prevent it spilling the condensate on to the floor. If it has a continuous drainage arrangement make sure that it can flow by gravity to a suitable drain. If the dehumidifier has a condensate drain that is great because it means that you can get the condensate to a drain more or less anywhere within reach of the hose that you attach to the dehumidifier and means you can leave the machine to work for long periods.

9. Consider putting air circulator fans into the building. If there is not enough air movement from the various machines in the building, the dehumidifiers, heaters, carpet dryers etc., you may discover that some areas are holding air pockets which are being left by the general air circulation. In this situation use fans to move the air in these areas.

10. Use a moisture meter to track drying progress. With active drying, there is a danger that walls and floors appear to be dry when they are still damp under the surface. 2 pin or 4 pin moisture meters can be purchased for as little as $50 dollars and they tell you what is happening in the wall rather than what is happening on the surface. If you don’t get this right, you might think your building is dry and as soon as you remove the dehumidifiers and drop the heat to normal levels, damp will reappear. Also use feel to determine how the building is drying. Drying of walls will start at the top of the wall and dry towards the base. As you run your hand over what appears to be a drywall, top to bottom you will probably notice the temperature of the wall cool, part way down. This will be roughly where the wall has dried down to.

These Building Drying Top 10 Tips are designed to give a brief overview of the challenge drying a building or perhaps a room. The Guidance and standards for drying flood-damaged buildings provides a really comprehensive guide to the subject and has much more information.


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Bill Anderson DEHUMIDIFICATION BLOG building dryer, Building drying, carpet dryer, dehumidifier, flood damage restoration,