One of the most frequent problems encountered in the home is damp, which can lead to mould.

Mould is a natural organic compound that develops in damp conditions and will grow on damp surfaces. This is often noticeable and present in situations where damp or condensation is present. The long-term solution to avoiding severe mould is to eliminate dampness

Residents living in homes with damp and mould may be more likely to have respiratory problems, allergies, asthma, and other conditions that impact on their immune system.  It may also have an impact on mental health if left untreated.

Causes of Damp:

There are three major causes of damp, which each require a different remedy. Damp occurs when a fault in the building’s basic structure lets in water from outside.

Penetrating damp – This can affect almost anywhere in the home and is usually the result of a building or plumbing fault allowing water coming in through the walls or roof, or through cracks. It can be identified by a discolouration of internal walls or ceilings, the presence of tidemarks, blown or blistered plaster and rusted nails in skirting boards and floor timbers.

Causes of penetrating damp may be due to:

  • Defective components – for example, external wall doors and windows, roof coverings
  • Defective or blocked rainwater gutter and pipes
  • Defective or leaking internal waste pipes, hot and cold water and heating
  • Systems
  • Water ingress through brickwork, leaks or defective design of the structure
  • Flooding – for example, due to burst pipes

Rising damp – This occurs if there is a problem with the damp proof course. This is a barrier built into floors and walls to stop moisture rising through the house from the ground. The usual evidence of rising damps a ‘tide mark’ on the walls that shows how high it has risen and sometimes an accompanying musty smell. Rising damp can affect any wall in contact with the ground and therefore can affect internal as well as external walls. It does not normally rise above about 1 metre (3ft) in height.

Construction damp, where damp is caused by a problem in how the property was designed.

Cold Bridging is an area of the home which has a significantly higher heat transfer than the surrounding area. This is typically where there is either a break in the insulation, less insulation or the insulation is penetrated by an element with a higher thermal conductivity. During colder periods this can result in additional heat loss at these points. Further, there is a greater risk of condensation forming, which can lead to mould growth. Areas where commonly cold bridging can occur are; Window and door openings, Lintels, Cavity Walls, Floors, Flat and pitched roofs.


Condensation occurs when the moisture in the air gets cooler and tiny water droplets appear on surfaces. There is always some moisture in the air, even if you cannot see it. If the air gets colder it cannot hold all the moisture and tiny drops of water appear. This is condensation. Condensation occurs mainly during cold, it appears in places where there is little movement of air for example in corners, north facing walls on or near windows, in or behind wardrobes and cupboards. If left untreated, mould will begin to grow.

Causes of condensation may be due to:

  • Excess Humidity – for example, pans do not have lids on when cooking and drying washing inside the property without adequate ventilation
  • Ventilation – for example, windows are not opened, trickle vents are closed, extractor fans are not used, furniture is placed too close to external walls
  • Inadequate heating
  • Defective insulation i.e. dislodged insulation in lofts
  • Overcrowding

The air we breathe also holds amounts of water vapour, depending on its temperature. If warm moist air is cooled by any cold surface it is no longer able to hold the same amount of water vapour. The air-borne moisture turns into droplets of water and collects on the cold surfaces.

How Much moisture can be produced in your home in a day?

Water Vapour source in an ‘average’ house per day

Approximate water generated (in litres)

4/5 people asleep


2 people active




Washing up


Washing Clothes


Drying Clothes





15.7 litres

Advice to help reduce condensation in the home:

Tenants can take a number of steps to prevent and reduce condensation building up in their homes such as:

  • Managing humidity levels in the home and maintaining a healthy humidity level of between 40-60%. This can be achieved by keeping levels of moisture to a minimum for example, covering pans when cooking, drying washing outside and keeping the kitchen or bathroom door closed when cooking or bathing
  • Adequately heating rooms – ideally between 18 and 22C
  • Keeping the property well ventilated, for example, opening windows when cooking or bathing, turning on and ensuring that the extractor fan is working, keeping trickle vents in windows open, and allowing air to circulate around furniture

Watch a short film for more advice.

How to Seek Help:

Private Tenants: If you rent your property from a private Landlord and suspect your home is suffering from damp or condensation, in the first instance the legal Tenant is generally advised to inform the Landlord in writing of any defects and ask for these to be rectified within a reasonable period from the date of the letter. You should keep a copy of this letter.

Please contact the Private Sector Housing Team for help and advice if after a reasonable time period (usually 28 days is sufficient), your Landlord has not carried out repairs/provided satisfactory assistance.

Council Tenants:

Council tenants can report an issue to Dartford Borough Council.

View the Council's Housing Damp & Mould Policy. for Council Tenancies.

Further Reading:

Gov.UK Guidance; Understanding and addressing the health risks of damp and mould in the home

Dealing with damp and condensation, NEA leaflet