Repair

Floodwater has the potential to damage a building in several ways. It can cause superficial damage to paint, plaster and finishes, or structural damage to the building fabric. These types of damage are direct effects of the flooding, occurring immediately. Indirect effects of the flooding may occur at a later date, such as mould growth, timber decay and so on.

The nature of the damage will depend on:

• the depth that the water reaches and its speed of flow
• the course it takes
• the length of time it remains in the building
• the materials used in the building
• the contaminants carried by the floodwater
• the length of time it takes to start the drying process

Although relatively resistant to flood damage, traditional materials can suffer some degradation and may need appropriate replacement or repair. The extent of the repair won’t necessarily be obvious until the building has been dried, and in some cases not until further monitoring has occurred.

Masonry

As long as the masonry of the building has not been covered in inappropriate materials, such as waterproof treatments, sealants, membranes, creams or cement or gypsum renders, then the masonry will be able to return to its pre-incident state.

Some repair might be needed if mortar joints have been particularly eroded, if structural failure has occurred, or where particularly soft brick of stone has lost its face via spalling due to freeze thaw.

Impermeable, heavily cement-based mortar will exacerbate deterioration during a flood because it holds the moisture in the masonry for longer resulting in salts crystallizing within the historic materials. Its wholesale removal and replacement with weaker permeable lime-based mortar will help the walls to dry out. Lime mortar joints can become weakened by these processes and by the long-term seepage of contaminated water through masonry, but they facilitate the drying of the whole building and are recognized to be a sacrificial layer that will require routine maintenance.

Identifying the appropriate materials for either masonry or mortar repairs is important to ensure the materials are compatible chemically and aesthetically appropriate. Information on stones can be found via the buildings stone database and via the sourcing stones guidance. There are likely also clues on the buildings listing description or in archival data.

Where existing mortar is present, an appropriate mix can be identified via samples sent to lime specialists for analysis. This however, cannot always guarantee that the mortar was the original or that it is still an appropriate mix. The mix should be established by ensuring that it is weaker than the surrounding masonry and has aggregates that are chemically compatible with the surrounding masonry. Generally, the aggregate for the lime mortar would have come from the same quarry as the masonry.

There are many types of lime and some evidence of historic earthen mortars. Lime work is a specialised area, and specifying and installing mortar requires experience and competence. If specialists need to be brought in from farther afield, this will be an additional project cost. However, their expertise will create a much more resilient building that is less likely to fail.

Masonry structures that have a rubble infill are very susceptible to damage from water penetration, because the water will dislodge the finer materials. This can cause the infill to fall from its original position, thus creating large voids and consolidation at lower levels. Where repairs are required an appropriately qualified and experienced professional should be involved in the specification and workmanship.

Earth construction

Cob (also known as cobb, clay-lump or clom) and other forms of unbaked earth wall construction can be particularly vulnerable to water damage. If moisture rises above the plinth for a prolonged period, or if it is trapped behind an impermeable surface, the cob will begin to disintegrate via slippage, collapse or rodent infestation.

It is important that any repairs undertaken to an earthen building use compatible and permeable materials, as well as someone with experience in buildings and repairing these types of structures.

Timber

Timber is used for various elements of a building; they could be structural, flooring, doors, windows, or aesthetic such as panelling. Timber when wet may warp, shrink or move following a flood and where left wet will suffer decay from fungal or pest attack. The extent of damage is dependent on how much water comes into contact with the timber and how long it is left in that condition.

Traditional joinery is a specialist area, employing different techniques that are no longer widely used. Works to historic timber fabrics will likely need someone with experience in understanding the original construction. It is important for them to be familiar with era-specific design details when repairing or upgrading existing elements, or when designing and constructing new ones.

Older timber is fairly resilient and should only require minor adjustments, such as rehanging or undertaking splice repairs where required.

Skirting boards, door frames and other items of internal joinery are likely to survive a flood intact. After drying they should return to their original size and form and can be retained.

It is becoming increasingly difficult to find a match for the timber species and/or timber quality used in original construction phases, thus consideration may need to be given to the introduction of a different species for repair. It is important to ensure that any new timber is as similar as possible to the properties of the original fabric. In addition, to prevent shrinkage, swelling, structural incompatibility and ultimately failure, the timber must have acclimatised to site's environment prior to being used.

Plasters and renders

The removal of historic lime plaster is rarely justified, as it will not inhibit drying unless it has been treated or coated with inappropriate finishes.

Older lime-based plasters may soften and swell when wet, usually without collapse, and harden again once dry. De-bonding of lime plaster can occur as the underlying laths swell and shrink when wet, causing breakage of plaster nibs. De-bonded plaster can be re-anchored using resins and screws. Alternatively, localized repairs can be undertaken by removing the failed sections and reinstating and chasing in new appropriate lime render/plaster which is then finished with a compatible covering.

It’s important to check for obvious cracks and areas where plaster has bulged on walls or sagged on ceilings. Some of this deterioration could be historic deformation unrelated to flooding.

Where wholesale replacement is needed, the opportunity to use lime-based products in reinstatement works, will afford greater resistance in any future flooding thus reducing the amount of repair work needed in the future.

Wall coverings and paintings

When wet, paper and paste can provide food for mould growth. Non-historic wall coverings should be carefully removed and discarded. Consult a specialist conservator about moving, cleaning and disinfecting historic wall coverings, whether of paper, textile, pressed metal, leather or other material.

Painted finishes

Water can cause the staining, flaking, blooming and dissolution of binders in varnishes and paints. Permeable traditional paint finishes, such as lime-wash, which allow moisture to evaporate through their surfaces from the substrate can be cleaned, disinfected and left to air dry or repainted to match.

Modern paints, such as alkyd oil-based paints or acrylic emulsions should not be used on lime plaster or render as they will impede moisture transfer.

Metalwork

Aluminum, bronze, copper and brass objects, components and fixtures will not be damaged by immersion in water as long as they are allowed to dry quickly. Iron and steel will oxidise and rust and expand when exposed to water, though they should not be harmed by a single immersion as long as they are dried quickly.

Rusting, particularly in maritime environments, can lead to serious structural problems where metal components such as steel sections or reinforcements in concrete lintels are embedded within saturated walls that do not dry quickly. Here, the exfoliation of oxidising metal sections or the expansion of the metal causing spalling of the concrete can reduce the bearing capacity of the beam or lintel and result in cracking, if not collapse. Check the lintels: cracks, deformation or oxide-staining (rust-staining) are signs of distress and should be inspected by a structural engineer.

Similarly, ties, cramps, pipes and conduits in masonry walls or floors can continue to oxidise and expand once rusting has commenced, leading ultimately to cracking and spalling of surfaces and possibly to localised de-bonding and structural failure. Simple surface staining can be cleaned, primed and redecorated.

Where ironmongery such as locks and hinges have dried out they can be dusted with powdered graphite to prevent squeaking and seizing. Historic metalwork can be temporarily lacquered or waxed by conservators to limit future damage by flooding.

Concrete

Though not a traditional material, many buildings have been adapted and had concrete floors and screeds installed. Once these materials become saturated, they can take a long time to dry. They also can potentially fail from exserted forces from the ground and need replacement. In these situations, wholesale removal should be undertaken and a new floor might need to be instated.