There are three types of damp commonly found in domestic properties:
where the dampness is rising up from the ground. Can occur when there is no damp-proof course or where it has been breached eg soil/path level is above the course.
It is usually found at ground floor level and leaves a tide mark low on the wall. Rising damp will be present all year round; however, it is more noticeable in winter. If it is not treated, it can cause wall plaster to crumble and wallpaper to lift.
Black mould is not usually seen where there is rising damp. This is because rising dampness carries with it ground salts which prevent the growth of black mould.
moisture entering through a building defect eg cracks in render, leaking roof, leaking gutters. This type of dampness is usually found on external walls or due to roof leaks on ceilings. It only appears because of a defect outside the home, such as missing pointing, cracked rendering, missing roof tiles or defective guttering and pipes. These defects allow water to pass from the outside to the inner surfaces. Penetrating dampness is far more noticeable following rainfall and will normally appear as a well-defined damp-patch which looks and feels damp to the touch.
Black mould may not be seen on areas of penetrating damp due to the affected areas being too wet and the dampness containing salts picked up when passing through the wall, which prevent the growth of black mould.
dampness occurs when there is an imbalance between heating, insulation, ventilation and humidity eg too much moisture in the room which then condenses against the coldest surfaces. Water produced from condensation is generally noticeable where it forms on non-absorbent surfaces (eg windows or tiles, bathroom ceilings) but it can form on any surface and it may not be noticed until black mould growth or rotting of material occurs.
Condensation mainly occurs during the colder months and can happen whether it is rainy or dry. It is usually found in the corners of rooms, north facing walls and on or near windows. It is also found in areas where there is poor air circulation, such as behind wardrobes and beds, especially if they are pushed up against external walls.
Possible health effects of damp and mould
- respiratory infections, allergies, coughing
- mild fever (more common in children)
- a blocked and/or runny nose
- pain or pressure behind the face
- a scratchy or sore throat
- aggravate asthma
- dry, red and cracked skin
- a raised, itchy, red rash (hives)
- itchy, red, watering eyes (conjunctivitis)
More recently studies also suggest that mould toxicity, a condition that occurs when mould toxins accumulate in the body, can also lead to symptoms of depression, anxiety, attentional problems, brain fog and insomnia.
How to prevent dampness
To prevent rising damp from damaging walls, modern houses are built with damp proof courses (DPCs). In older houses, DPCs can become damaged over time, could be installed improperly or be bridged by adjoining works or soil/land. When houses are modernised or extended, the building works can affect built-in DPCs. Ground level changes can bridge the DPC layer to cause rising damp. A remedial DPC must be installed to prevent rising damp from recurring in these instances. Tanking* may also need to be considered.
*Tanking is the process of creating a tank-like seal to protect walls from water soaking through.
Preventative measures include regular maintenance of gutters, downpipes, roof and windows to ensure water is not penetrating into the property. Checking renders and pointing regularly for early signs of damage also stops moisture entering.
Regular property maintenance can help to prevent penetrating damp. Plumbing and central heating are common causes of damp within the home. Boilers must be checked annually in all rented properties. It is advisable that owner occupiers do this too. Plumbing works should be regularly checked to ensure that pipes are not corroded or leaking. Small leaks have been known to drip onto adjoining walls for a long time before anyone notices.
The control of condensation requires a combination of sufficient heating, ventilation and insulation.
By introducing low-level heating, the temperature of internal surfaces will rise. This will reduce cooling of any moisture-laden air and, as a result, the amount of condensation.
Ideally, low-level background heating should be continuous, as any short bursts of heat may not result in a suitable rise in surface temperatures.
Thermal insulation, such as loft or cavity wall insulation (where appropriate), internal wall insultation, draught proofing and double glazing, will help to reduce the amount of heat lost from a property. This will not only help keep internal room temperatures higher but will also help to keep fuel bills down.
Adequate ventilation is essential to allow moisture-laden air to escape from the home before condensation occurs. Extractor fans in the kitchen and bathroom can prove very effective in reducing condensation, especially when fitted with an effective humidistat control.
A property should be suitably constructed to accommodate the normal daily living requirements of tenants without the build-up of damp and mould. It is a common mistake to assume that condensation will be resolved by the resident adjusting heating, ventilation, or moisture in the air. Landlords should avoid taking actions that solely place the onus on the resident. They should consider what they can put in place to support residents in cases where structural interventions are not appropriate and satisfy themselves they are taking all reasonable steps.
Occupants can help to reduce condensation and prevent mould growth by:
- pull wardrobes and furniture away from walls, and keep tops of wardrobes clear, to allow air to circulate effectively
- open windows when cooking, or if they are installed, keep the trickle ventilators open
- keep lids on saucepans when cooking, keep the kitchen door closed and ventilate the room
- keep bathroom doors closed when bathing, and open windows slightly afterwards
- do not dry clothes on radiators, unless ventilation is increased
- if a property is over crowded this can increase condensation
- a very common area for mould growth is around windows this can be cleaned with an anti-fungal solution
We would urge landlords to be proactive in their approach to all property repairs, including damp and mould, not waiting for the tenant to raise complaints but ensuring quarterly visits are undertaken.
Damp is a very complex area and can be caused by several factors and often requires numerous interventions to prevent. It is advisable that landlords appoint a damp specialist who is a member of the Property Care Association, for example.
As landlords are being required to increase the Energy Performance Certificate scores for their properties and reduce carbon emissions they need to consider and plan for how they can identify and respond to potential unintended consequences around damp and mould.
We would also encourage landlords to review, with tenants, how they respond to reports of damp and mould to ensure they avoid automatically apportioning blame or using language that leaves residents feeling blamed.
Landlords need to be aware of the health impacts of damp and mould and ensure that their response to reports of disrepair are timely and reflect the urgency of the issue.