Sources of moisture

Very recent flooding

• news reports and news archives may reveal current or recent flooding events;
• the fire brigade are in attendance and pumping;
• sandbags at door/gates, or stored away from view;
• mains services turned off/temporary supplies;
• dehumidifiers/ventilation maintained;
• piled/damaged household effects;
• opening up evident, e.g. occasional floorboards lifted to aid drying out;
• drain holes for release of moisture; and
• presence of disinfectants evident.

Past flooding

• historic news reports;
• local authority or district council knowledge;
• openable flood barriers at boundary wall openings, presence of sandbags, boards or coverings to door/window/airbrick openings;
• an earlier high water level evidenced by staining/tide mark on external walls;
• build-up of visible sludge/silt externally or internally;
• contamination by river or sea water (the presence of certain bacteria can be a health risk);
• structural damage from weight and pressure of water, damage to footings;
• trapped water in voids, cavities, under impervious coverings/finishes;
• silt build up in voids/cavities;
• doors/windows sticking/distorted;
• damage to soft core materials of fire doors;
• staining to wall finishes, floors, etc.;
• wholesale renewal of furniture, carpets, fabrics, white goods, etc. or furniture/effects raised off the floor; and
• rowing dinghy tied to iron stake.

Material damage/condition

• timber significantly damp at depth;
• vulnerable timber type such as non-water resistant chipboard damaged (kitchen units against walls or floors should be checked);
• insulation materials soaked/displaced;
• plasterboard damaged;
• gypsum-based plasters damaged/deteriorated;
• corrosion to embedded steel, electric sockets, conduits, fixings, plaster beads;
• cracking/damage to materials caused by wetting/drying cycle;
• timber rot;
• frost damage to low level masonry;
• efflorescence to masonry faces; and
• water in double-glazed units.

Earlier remedial works after flooding

• raised electrical fittings and sockets, etc. at ground floor;
• fitted carpet renewal, or replacement by removable coverings, tiling exposed as finish;
• joinery replacement;
• timber skirting replaced by plastic;
• replacement timber flooring;
• renewal of kitchen units;
• renewal of electric storage heaters and floor mounted gas boilers;
• re-plastering;
• redecoration; and
• changes in use of internal space.

Pre-existing and potential defects to buildings contributing to dampness unrelated to flooding

When examining a building post flood incident, it is important when assessing the property for specialist drying to take note of any of the following which may indicate dampness existed in the building prior to the flood, as this may hinder the drying process (Mike Parrett’s guide to building pathology).

• Defective rain water goods.
• Defective roofing.
• Defective drainage.
• Blocked cavity wall voids.
• Types of cavity wall insulation where rainwater penetration through the outer leaf wall soaks the material.
• Defective external mortar courses and perpends.
• Defective and blocked cavity trays and without drainage tubes fitted to the perpends.
• Evidence of retro-fit chemical dpc injection.
• Evidence of internal vapour check insulation wall and ceiling boards.
• Replacement solid floors.
• Embedded metal potable water and heating pipes in solid floors.
• Older and historic building original features; flagstone floors, natural hydraulic lime rendered walls, cobb walls etc.
• Ill-fitting or poorly maintained original timber windows, doors and frames.
• Fire hearths without dpc to the fender walls.
• Timber boarded and battened flooring laid directly onto a clinker ash substrate, typical of the inter-war building era.
• Magnesium oxychloride floor screeds; typically in buildings from 1930s through to 1950s – highly susceptible to moisture.
• Different genres of buildings with solid ground supported floors constructed without any dpm.
• Evidence of any timber decay to building elements prior to any strip out as a result of flooding.
• Owner/occupier information about any pre-existing dampness, mould present within the habitable spaces prior to the flood incident.
• Evidence of poor DIY and or alterations/additions to the building post the original construction.

Please note: there are a wide and varied number of inherent defects to buildings of different genres with an increasing number of undiscovered latent defects associated with new and recent buildings less than 10 years of age. There have been many cases listed with insurers where drying certificates have been issued to complete the reinstatement of a flooded building only to discover dampness returning not always as a direct result of the flood, but due to pre-existing defects and ill-conceived alterations to the buildings.

Building surveyors need be more fully aware of the requirements of a pathological building examination, a history of known building constructions and their short falls from a dampness perspective. They should also carry out a range of testing and measurement to a stage 4 investigation and if required a stage 5, which would require destructive/ invasive testing and longer term monitoring.