Main Types of Damp

Discovering that the home you are selling or buying has damp does not necessarily mean that the property has a structural defect.  The word ‘damp’ in residential property terms tends to cover three main types namely:

1. Rising Damp.

2. Penetrating Damp.

3. Condensation.

Each one needs to be treated in a different way which in turn means the damp repair costs can vary dramatically.  That’s why first off, it is important to know what you are facing.

Rising Damp

Typically, however not exclusively, rising damp is more associated with older properties.  The legal requirement for a Damp Proof Course (DPC) was first introduced in 1875 where a layer of slate was used in between the brick and mortar work.  Therefore, Georgian and early Victorian properties would not have been built with a DPC and if these properties do have one, it would have been added at a later date.

The telltale signs are normally damp skirting boards, flaking paint or plaster and a watermark.  Black spot mould is not typically present and if it is, it is likely to be one of the other kinds of damp.

A DPC, be it a membrane or chemical injection, is very effective at preventing rising damp.  It is unusual for a DPC to be damaged and therefore when there is a diagnosis of rising damp and a DPC is present, it is worth asking the following questions:

1. Has the DPC been bridged?  i.e. if there something providing a link from the ground and going above the DPC?

2. How high are the external ground levels?

3. Could any cavity wall insulation be compromising the DPC?

Answering the first two questions is relatively easy and can be done with a physical walk around the external walls.  Drain pipes, plants, and trellis work can all potentially bridge a DPC and current building regulations recommend at least 15 cms between the DPC and the ground.

The key thing to remember with rising damp, (the clue is in the title!), is that due to capillary action, the damp rarely goes above 1.5 metres.

Penetrative Damp

Penetrating damp is caused by water leaking through walls.  This type of damp may expand across walls or ceilings and typically will move horizontally, rather than by travelling up walls (as is the case with rising damp).  Penetrating damp is usually caused by structural problems in a building. Things like faulty guttering or drain pipes, damaged roofing, cracks in the walls, damaged chimneys or windows can all provide ways of water entering the property.

Most of the time, once the cause has been identified and fixed, there is likely to be some remedial work to do and it is best to make sure the damaged area has dried out completely.

Condensation

Condensation is the most common kind of damp.  It is caused by moist air condensing on walls, particularly in rooms with a lot of air moisture, such as kitchens and bathrooms.  It's mainly, but not always, a winter problem, as the walls are much colder than the air inside.

Issues around condensation are usually alleviated with improved ventilation.  Problems can occur with older properties, which were typically built to ‘breath’ and dampness would just naturally evaporate out of the property.  Applying modern building standards to these older properties can mean that the natural circulation of air is halted or concentrated in certain areas.  Closing up chimneys and installing double-glazing may provide warmth but they can also lead to reduced air circulation.

Reducing the amount of condensation is about managing the air flow.  For bathrooms, open the windows and keep the door closed. Having an extractor fan also helps.  It is similar advice for the kitchen where windows and extractor fans help get the warm air out and closed doors stop it spreading and then condensing.

We deal with all types of property on a daily basis and know that damp does not have to be a showstopper, however, it is worth getting further professional advice.

For all things property, why not drop into our office in Faringdon for a coffee and a chat.