Understanding Drying

There are several stages to drying out flood damage. The amount of water, construction and materials of the building, as well as ambient conditions, will determine the total time needed to achieve original background levels of moisture in the fabric of the building. This is the aim of the drying procedure - to be achieved before remedial building work begins.

1. Having ensured that it is safe to enter and commence work with the appropriate assessment of any risks having been completed it is clearly important to clear any standing water and remove absorbent materials for restoration or disposal. At this stage it will be necessary to determine the extent of invasive works needed to permit adequate access for drying to take place. Permission for some invasive work will be needed.
2. Ventilation of the area may well be helpful in the initial drying stages but this will depend on the outside conditions. Clearly cold and humid outside conditions will not aid the process. At this stage the humidity inside the affected area is likely to be very high and a judgement will need to be made as to whether a high level of ventilation or heating and dehumidification will be most effective. Initial drying involves evaporation from wet surfaces. Dehumidification equipment utilised at this stage needs to be capable of maintaining around 50% relative humidity and disposing of the volumes of water collected. Refrigerant based systems are suitable.
3. Once visible moisture on surfaces is evaporated the process of drawing the moisture out of materials will begin. Surface may, at this time, appear dry to the touch but large volumes of water may be held within the structure and time will be needed for this to move by capillary action to the surface from where it can be evaporate into the air and removed by drying of the air. Drilling into the material and measure damp levels within the structure will be needed to monitor drying.
   The rate of moisture removal will depend on the temperature and relative humidity of the surrounding air. The higher the air temperature the more moisture it can hold at a given temperature and therefore the greater it's ability to transfer that moisture away. At this stage some heating may be advisable along with the use of fans to ensure good circulation into areas which might otherwise take longer to dry. Whether there is a need to switch to desiccant based dehumidifiers to achieve lower relative humidity and accelerate the drying will be a judgement on the part of the technician.
   Regular monitoring of agreed locations where drilled monitoring points are established will show progress towards full drying and when normal background moisture levels are being achieved.
   When fully dry a Certificate of Dryness will be issued to allow repair work to commence. Throughout the drying process avoiding condensation on adjacent surfaces is important particularly in colder weather when cold outside walls may be prone.