Understanding Damp and Mold

Damp occurs when there is excess of unwanted moisture in the air that has no way of escaping. Excess moisture can be caused by steam when cooking, drying clothes inside the home and perspiration caused through showering and bathing. 

 

There are 3 types of damp: 

 

 

 

Penetrating damp is the process of moisture moving from the exterior wall of a building to the interior. It occurs when outside moisture, like wind-driven rain, impacts a building's wall. Building materials like brick are porous. They soak up rain to saturate the wall with penetrating damp. 

 

 

Rain penetration into masonry can occur in buildings of all ages. At its most obvious, it penetrates the wall and displays as a damp patch on the internal wall. This causes discolouration, paint and wallpaper peeling and flaking. 

Even if it does not penetrate entirely through a wall, rainwater penetration can be damaging to a property. Wind-driven rain in masonry can cause moss growth, increased heat loss and frost damage. 

 

 

 

Rising damp happens when water rises from the ground through the floor and into the walls of the building. You can often see rising damp because it leaves a tide mark low down on affected walls. 

Compared to penetrating damp or dampness caused by excess condensation, rising damp is relatively rare. 

In older buildings over 100 years, it is often caused by a faulty or missing DPC (Damp proof course). 

In newer buildings, rising damp is often caused by adjoining structures that introduce moisture above the DPC. 

 

 

Dampness in walls originates from a variety of different sources. It is therefore important to find out exactly where the dampness comes from to save time and money on the wrong treatment. 

 

Internally, the rising damp can be identified by looking at the following signs: 

 

 

 

 

 

Rising damp is often the cause of structural damage in buildings. Internally rising groundwater saturates walls and pollutants. Saltpetre, which is contained in water, damages building materials. With time, constant dampness in walls can lead to mould, blistering, the peeling of paint and wallpaper and damaged render. 

In older buildings, this type of damp is often caused by a damaged DPC or the lack thereof. Relevant building regulations for damp-proof courses were developed in the early 1900’s. However, these were not always adhered to. As a result, some of these DPCs become damaged over time. 

 

 

 

 

Condensation is by far the most common cause of dampness in buildings, probably accounting for the majority of damp problems reported. It affects both old and new buildings, but it appears to be a significant problem where the building has been modernised. 

Condensation is directly associated with mould growth. It is this that the occupier sees first, and it gives an indication of the potential scale of the problem. The mould is usually found on decorative surfaces, especially wallpapers, where it can cause severe and permanent spoiling. In many cases, the mould and its spores (‘seeds’) give rise to complaints about health, and cause the “musty” odour frequently associated with a damp house. 

 

 

If humidity is high enough, the accumulated moisture in the air is deposited on cold impenetrable surfaces. This can cause condensation on the outside and inside of windows. Condensation can also form inside double-glazing, although that is usually caused by a failure of the seal between the two window panes. Condensation can also affect penetrable surfaces, such as wallpaper and plaster. The perfect conditions for condensation to manifest are: 

 

 

Warm air holds more moisture than cold air and when it rises, so do the suspended water molecules that are contained. As temperatures fall, the air can no longer hold all of its moisture, so it will find surrounding cool surfaces to transfer this moisture onto. 

 

Condensation is very much a seasonal problem, occurring during the colder months – October to April. During the summer, the problem is seen to go away. During the winter, ventilation of the house is usually low (due to windows and doors being closed, draught-proofing takes place). This allows build up of water vapour in the house, which, in some cases is sufficient to cause condensation. This condensation becomes apparent from the following symptoms: 

 

 

Condensation is common in areas where there is little air movement, such as: 

 

If a property doesn't have good ventilation and heating, condensation can cause mould. Mould is a type of fungus which grows in damp conditions. Its spores can make some medical conditions worse, such as: 

 

 

 

- Reduce moisture by wiping any damp or wet windows, sills, walls and surfaces with a paper towel and throwing it away. 

 

 

 

It might seem strange to keep the heating on with a window slightly open, but it helps because you're letting air that's full of moisture out and dry air in. Dry air is easier and cheaper to heat. 

 

 

 

 

 

The most crutial thing when dealing with any type of dampness is to react promptly. Water can make a lot of damage to your property, thats why it is important to notice early signs. Share this article with your tenants and ask them to report anything suspicious as soon as possible.