Fixing flooded buildings and basements: How to dry

The following Sections provide an overview of some of the key technical issues involved in repairing flood damaged properties, and with drying standards, methods of drying, typical equipment and methods of monitoring.

Often for flood-damaged buildings, the most appropriate method to be used needs to be decided by the expert, with full knowledge and understanding of the facts and conditions. For this reason there has been no attempt to prescribe the most appropriate solution for any given circumstance.

It is also recognized that there continue to be advances in drying technology which are the subject of continued discussion and debate between industry experts. It is not the intention of this guide to contribute to that debate, but rather to provide a basic understanding of the methods and equipment available.

19 After all standing water has subsided, drying out continues by removing waterlogged and damaged carpets, furniture and fittings - virtually everything in contact with water or moisture which is not part of the fabric of the building

Minimum drying standards

When can a building that has been affected by water be considered dry? The underlying principal that has guided the development of a minimum standard of drying effectiveness is that the moisture levels found in the property after the damage should be reduced to levels that existed before the flooding.

The building materials and general structure of the property - floors, walls ceilings, doors etc - must be returned to their pre--flooding moisture condition. These criteria must be achieved before it can be accepted that drying equipment and services are no longer required; they would be considered sufficient when the following have been achieved.

* The condition of internal construction materials is at or better than that normally considered acceptable, or compares favorably with areas not associated with the flood

* The moisture on and in the building materials will not support the growth of mould and mildew

* The levels of trapped or bound water within the building envelope, construction materials or contents will not migrate or transfer to areas or surfaces which may promote mould growth, because failure or damage to areas restored or repaired, or damage to previously unaffected areas.

Primary and secondary damage

Primary damage is caused directly by floodwater penetrating building materials and components to the extent that they are permanently or temporarily affected and unable to maintain the functions for which they were designed or produced.

Secondary damage is caused after the initial flooding, typically by the migration or movement of water or moisture from the initial flooded areas to areas clearly not previously affected. It is usually avoidable by prompt action following the flooding event.

A normal, well maintained building has a low level of moisture held in the building structure - too low to support the growth of fungi. Most moulds and other forms of fungi don't grow in conditions where the moisture levels are in equilibrium throughout the property, and safely below levels that encourage growths. After a flood event this balance is disturbed.

When water soaks into a building and its materials, they become wet enough to support fungal growths and drying out is therefore essential.

Additionally, as water evaporates from these wet materials it can travel as moisture in the air and be absorbed by other materials remote from the area initially affected.

Damage from fungal growths is considered to be secondary damage and is avoided by early action. It is generally accepted that some growth will occur within 2 to 3 days of the building being affected by water, coupled with resultant high levels of humidity.

Where secondary damage occurs and there has been no fault on the part of anyone involved, insurers will usually deal with this damage as part of the original claim.

Triage, clearance and cleaning

The remediation phase after flooding should follow a common sense approach. The following points should be considered.

Damage inspection

Identifying the full extent of primary damage and possible secondary damage will provide the necessary information to undertake the following triage assessment.

Triage assessment

This is the assessment and planning of the most pressing actions required to mitigate or control the damage. The outcome of triage usually requires action within the first few hours (the golden hours) after the floodwaters have receded. Typically this is when obvious salvageable house contents are moved out of harm's way in order of greatest value or significance.

Clearance up

Before any building, drying or restoration work can commence, the affected areas must be cleared to allow cleaning and decontamination. This must be seen as a first step, but taking photographs, logging all actions and obtaining loss adjuster's or insurer's permission before disposing of insured damaged items are a necessary part of this process.

Cleaning

Floods of all types will bring into the home a variety of contaminants and , while wet, they are generally prevented from becoming airborne. It is therefore sensible to remove these contaminants while they are still wet together with the silt often associated with flooding. Simple personal protective equipment (PPE) will be needed to provide the required safe conditions where silts have already dried.

Using garden hoses or power jetting can significantly speed this cleaning and contaminant removal operation, but, where thick deposits are present, shovels may be a better choice.

No attempt should be made to dry the building until all wet cleaning has been accomplished although starting to dry out upstairs areas by ventilation can be considered. Removing perimeter floorboards to reduce the effects of swollen boards pressing against and damaging walls should also be considered.