Protecting premises from damp after storms

While this winter might be unseasonably warm, it certainly hasn’t been dry. As the north of England cleans up from the devastating storms Desmond and Eva, Building and Facilities Managers should be thinking about damp and taking precautions to prevent a problem further down the line. The old adage ‘failing to prepare is preparing for failure’ certainly rings true when it comes to damp. By the time a damp problem becomes visible, the damage can be well and truly done – impacting not only your property, but also potentially on the health of the occupants within. Here, we’ll explore the precautions you can take to prevent a damp problem in your building, the tell-tale signs to help you identify it as early as possible, and what to do if a problem arises.

What is damp and how does it occur?

Simply put, damp is unwanted moisture in the structure of your building. It can undermine the structural integrity of your property and inflict serious damage to its interior, causing cracked plaster, peeling wallpaper and rotting skirting boards or structural timbers. Some forms of damp have an immediate effect, for example it is a common by-product of flooding. Other forms of damp develop over years, either through external or internal forces.  These are the three most common forms of damp:

  1. Rising damp – This occurs if a property does not have a physical damp course, or if this breaks down. Raised flowerbeds or paving against walls can also bridge the damp course. If damp patches on walls appear on wet days and disappear on dry days, this can indicate the presence of hygroscopic salts, often as a consequence of rising damp. These salts pull in excess moisture from the air and make the wall surface damp, but when the air dries, so does the wall. Damp can also arise as a result of damage caused by blocked drains, or surface run-off hitting a wall during heavy storms, like those that much of Britain experienced over the Christmas and New Year period.
  2. Penetrating damp– This may take some time to become apparent. If your property is exposed to the prevailing wind (usually south-westerly), this can drive rain into the masonry, which can then pass through solid walls into the plaster. This form of damp may also cause efflorescence (salting) on the masonry. Property defects such as cracked render, gaps around windows, defective ‘rainwater goods’ (guttering, downpipes etc...) leaking roofs and plants growing on the building can all cause moisture to enter a property. Penetrating damp can also occur when groundwater passes through basement or earth retaining walls. 
  3. Condensation – This is the consequence of the production of moisture within a building, which is most commonly seen between October and April, when ventilation is reduced as windows are closed, and there is a big difference in temperature between the interior and exterior of the building. Air only holds a certain amount of water before it precipitates on cold surfaces as condensation, causing damp patches on walls and around windows. This in turn can lead to a build-up of mould.

What are the risks?

Property damage is a significant risk. Damp will most frequently manifest as a wet patch in the roof, floors or walls, but could also signal underlying structural issues. The cost of repairing a damp problem is entirely dependent on the extent of damage to the property and the type of damp. This can range between from a few hundred pounds, to tens of thousands depending on the problem. It’s therefore critical that building managers remain alert to the signs of damp and take the necessary precautions to prevent it entering a property. Damp can also lead to mould growth, which may create health risks for your building’s occupants. The moist, stale air, mould spores and increase in dust mite populations, can adversely affect the health of the occupants. While some people are more sensitive to moulds caused by damp than others, the risks should not be ignored by buildings and facilities managers, particularly if asthmatics are present.

Signs of rising damp on exterior brickwork

Buildings in the UK should have a damp proof course that acts as a barrier to stop water being drawn upwards within the walls of the property. While this has been a legal requirement in all properties built after 1875, this alone does not make all buildings immune to damp problems. Here are some relatively simple tips to help prevent damp:

• Ensure that external ground levels are a minimum 150mm below the current damp proof course. If they are not, this can result in ‘bridging’, whereby water enters brickwork or mortar above the damp course via splash-back in particular
• Ensure there are sufficient air bricks to provide ventilation to the timber sub-floor, that they are uncovered and located approximately every 1.8 metres
• Ensure that any brick walls that do not have a damp course do not touch the main building, as this can result in ‘bridging’
• Check for signs of dampness on walls and skirting boards. Rising damp on walls rarely exceeds one metre above ground level, but may go higher in extreme cases
• Perform regular checks of rainwater goods such as drains and downpipes to ensure there are no blockages or leaks, and fix any faults immediately. A small drip can over time create a much more serious issue
• Inspect flashing on the building’s roof and around windows to ensure it prevents water from entering the building
• Seal any cracks and crevices around the building

What should I be on the lookout for?

Catching a potential issue early can save you a lot of heartache and money! Here are a few tell-tale signs of damp:

• A musty smell in the building
• Formation of mould or mildew on walls
• Staining of wall coverings, peeling wallpaper & blistering paint
• Discolouration on walls or fragmenting plaster
• Nails or screws showing signs of rust on skirting boards or within plaster work
• The appearance of salt stains on exterior walls and crumbly mortar

What do I do if my building shows these signs of damp?

You should approach each individual source of damp separately and take the appropriate steps to cure it. Different sources of damp require different solutions, so it is advisable to treat them as individual incidents, instead of trying to implement a singular, universal solution.
When the source of the damp cannot be easily identified, or if you believe you may have a damp problem, do not hesitate to contact a damp specialist such as Rentokil Property Care, who can deal with the issue as quickly and effectively as possible. Damp specialists are also likely to be able to spot damp in areas that you yourself may not have identified. Rentokil Property Care has created a specialised Damp Rod treatment, which comes with a 30-year guarantee which can be passed on to the new owners, when a property changes hands.

Final Thoughts – prevention is better than a cure

With the increased rainfall experienced in Britain over the last few years compounding our typically moist climate, damp is becoming an increasing issue for building and facilities managers. Prevention is most definitely better than cure, so be diligent in checking your property and follow the tips provided. If you’re unsure, contact a trained professional. Any delayed action can result in further structural damage to your property, as well as increasing the cost of any repair work that may need to be undertaken.