Recoverability Measures
Recoverability measures are those that reduce the impact of flooding on a property. They can speed up recovery after a flood and help the occupant to move back into their building sooner.
The flooding industry recommends various measures to make a building more resilient. The following section describes only those that are appropriate for buildings of traditional construction and with heritage value.
Renders, plasters and mortars
Many PFR surveys suggest making walls waterproof by introducing water-resistant coatings, such as membranes, sealants, cement, gypsum, plasterboard or waterproof magnesium oxide boards. These methods are appropriate for modern buildings, but they are all known to cause decay and moisture issues in buildings of traditional construction. Using or recommending these methods may lead to fabric deterioration or failure, potentially exposing occupants to damp and mould.
Removing historic lime plaster from a surface is rarely justified. The lime plaster does not inhibit drying, and its relative connected porosity should, in fact, assist substrate drying. This is because materials that are compatible with traditional buildings are vapour and moisture permeable. Unless continuously wet (submerged), such materials will see liquid and vapour levels ebb and flow within them, naturally dissipating excess moisture back into the environment.
The type of masonry unit will also influence drying behaviour. In an impermeable stone rubble wall (such as granite), only the lime mortar is permeable and facilitates drying. But in a permeable stone wall (such as sandstone), drying can occur through both the stone and the lime mortar. It is important to allow water to be drawn out of the stone and into the sacrificial mortar to prevent damage to the masonry units.
For listed buildings specifically, it is beneficial to record the exact materials and mixes used for plasters, renders and mortars, as well as any finishes. This information will be useful for the homeowner should they need to provide evidence to an insurer if a flood were to occur in the future.
Floors
Many historic buildings have changed since their original construction and have seen modern materials used in their walls, floors and additional extensions. Historic fabric has been lost and solid concrete or insulated floors added. This has resulted in the hygroscopic nature of the building being changed, and its ability to buffer moisture reduced.
Solid tile or stone floors are naturally resilient and require only sweeping and cleaning after a flood. Lime or earthen mortar joints facilitate moisture evaporation. Where the existing floor is a modern intervention, such as a concrete floor, it may be possible to remove it after a flood and replace it with something more appropriate and recoverable. Options include a timber suspended floor or a limecrete floor, designed for a flood zone.
New timber suspended floors should be designed to be easily lifted to facilitate drying. It is not advisable to insulate underneath a suspended timber floors unless the insulation can be removed prior to a flood event. Adding a sump and pump system will also speed up the recovery process after the event.
When considering a limecrete floor, many people want to insulate it using a foamed glass aggregate and geotextile membrane system. However, the manufacturer's technical advice is that this system will not perform thermally in an area with a high-water table or where flooding might occur. It will not retain its insulation qualities if it gets wet. A foamed glass aggregate system should be installed at a minimum of 300mm above the highest point of groundwater. Alternatively, the system can be used as a capillary break, or with a damp-proof membrane. The compaction of the foamed glass aggregate materials will prevent a degree of movement from the force of groundwater flooding, but it may still cause the floor to fail.
Kitchens
When renewing or replacing a kitchen, consider which materials to use. Water-resistant materials, such as stainless steel, and solid wood cabinets will be easier to clean and will suffer less damage than MDF.
Consider also the depth at which the floodwater occurs. It may be better to position kitchen appliances off the ground, perhaps on a plinth.
In areas where flooding is expected to reach a high level, it may be advisable to relocate the kitchen to the first floor. This will allow the building to be used during and after a flood, reduce the need to replace cabinets and appliances, and improve recovery times.