Penetrating damp occurs when water moves from one side of a wall, ceiling, roof or floor to the other.
Examples:
- a broken tile causing a leaking roof
- broken sealant around a window letting rainwater in.
Consultant Building Pathologist, Michael Parrett Associates
RICS would like to thank Professor Michael Parrett FRICS for his help producing this consumer guide and for providing the photographs.
This consumer guide helps owners and occupiers of residential property to manage and maintain their homes.
Damp can be described as ‘excess moisture that should not be there’.
If any part of your home
you should investigate.
Damp comes from many sources and can take different forms:
Penetrating damp
Condensation
'Rising damp'
Penetrating damp occurs when water moves from one side of a wall, ceiling, roof or floor to the other.
Examples:
Penetrating damp, 'rising damp' and condensation are not causes of damp but are different ways moisture moves through, or onto, parts of a building.
To solve a damp problem, you first need to find where the moisture is coming from.
Finding the cause(s) of a damp problem can sometimes be complex, and it is best to contact a specialist building surveyor and ask for a Joint Position Statement (JPS 2022)-compliant survey.
However, anyone can investigate and look for problems. For example, you could go outside in the rain and see whether your gutters are overflowing. If something doesn’t look right, it usually isn’t right.
Check for:
When indoor temperatures drop or humidity is high, water vapour in the air turns into liquid droplets on the coldest surfaces in a room. This is commonly seen as condensation on windows, walls or other surfaces.
This can lead to mould growth forming over time on surfaces, typically:
Things that can increase condensation in your home are:
Firstly identify the source of the moisture.
Finding the source requires a methodical approach over time and you may need professional help.
Fix defects in the property.
Use windows and extractor fans for ventilation.
Opening windows does not always work when there is high humidity outside, so use extractor fans too.
Always use extractor fans while cooking, bathing or showering.
Check the ventilation systems in your home.
Keep kitchen and bathroom doors closed and windows open when in use.
Cover pots and pans where possible during cooking.
Maintain internal heat levels.
Keep your home well-ventilated and maintain internal heat levels, ideally between 18C and 21C.
This will reduce the likelihood of condensation and mould spores forming.
Internal temperatures below 18C may impact the health of pre-school-aged children, the elderly and those with existing health conditions.
Fuel poverty:
For those struggling to pay heating bills, there is advice from various platforms to 'heat the person, not the home'. However, not heating your home adequately can contribute to condensation and mould issues. If you can only heat yourself, remember that your home still needs ventilation.
Consider upgrading your windows.
If you own your home, you can address heat loss by upgrading your windows (especially if you upgrade from single-glazing to double- or triple-glazing or secondary glazing) − but remember that this will not address the source or amount of moisture in your home.
You may also need to increase ventilation, as modern windows have tighter air seals than older, draughty windows.
Finally, regularly wipe up condensation.
Wipe off daily with a dry cloth or sponge from around cooler places, like window areas and tiled wall surfaces in bathrooms and kitchens. This helps prevent mould growth.
If you are renting your home, report any concerns to your landlord or managing agent.
If you are finding it difficult to heat your home, you may be entitled to government help.
Citizens Advice’s page Struggling to pay your bills has links to other organisations that can help.
The term mould describes fungi that thrive in damp conditions.
There are thousands of different mould species found in the home. The most serious are those that release mycotoxins.
Mycotoxins are extremely harmful poisons, which can be inhaled, eaten or absorbed directly through the skin. They can lead to poisoning, and in the long term can cause certain cancers and immunosuppression-related illnesses. Asthma and other severe respiratory conditions can also be triggered.
The first step is to identify and remedy the source of moisture. Mould treatments can only address the symptoms of dampness, not the underlying causes. These need to be properly understood and often require an independent chartered building surveyor who specialises in building pathology to investigate.
It is essential to remove mould in your home promptly and daily to reduce health risks. For hard surfaces, use mould and mildew cleaning products (which are more effective and safer than bleach) and leave them to dry completely.
Mould removal itself presents a health risk, so during cleaning:
Lock cleaning products away and keep them well out of the way of children, as they can be very harmful if ingested.
Larger areas of mould (such as a substantive part of a whole wall or ceiling) should only be addressed by qualified professionals. If you are renting your home, tell your landlord or managing agent about any mould that is causing you concern.
Absorbent materials such as carpets, soft furnishings and ceiling tiles might need specialist cleaning if they become mouldy. It may be difficult or impossible to remove the mould completely.
Mould on corner walls
Mould in a living room
No home is completely immune from condensation and mould formation. They are natural processes and require managing.
Repairs, maintenance and management apply to everyone to differing degrees, whether a homeowner, tenant or landlord.
Do:
carry out regular maintenance to keep your building as dry as possible, for example:
Do not install expensive damp-proofing measures without carrying out routine maintenance work, or considering what has changed and addressing that, first. In some types of home (for example older buildings with solid walls), damp-proofing measures may not be appropriate and may exacerbate damp issues.
Always seek advice from a building surveyor before making changes to your home or garden. This avoids the risk of creating problems. For example:
Remember that changes to a building may require local authority planning consent and/or building regulations approval using an approved certified contractor.
Size/volume matters. The volume of space inside a property stays the same, but the number of people (and pets) living there changes. Where homes accommodate more people, more consideration of moisture management , e.g. additional ventilation, may be required.
Always take a holistic and proactive view when trying to solve a damp problem in the home. Think about all the sources of moisture, and think about whether you can make any small modifications to your daily routine to reduce moisture.
If there is a significant damp and mould issue, it’s critical to approach the right kind of building surveyor.RICS membership does not automatically mean a surveyor is suitably experienced in damp and mould. There are many different kinds of RICS members: valuers, quantity surveyors, etc.
A JPS 2022-compliant inspection report will give you an unbiased professional opinion from someone who does not have a commercial interest in selling you a product. The report will only suggest remedial works that are proportionate and that respect the nature of the property.
Be wary of any surveyor or commercial specialist who uses only a damp meter to diagnose the source of dampness, especially in hard walls and solid floors.
Damp meters test an electric current through a material. They are accurate for measuring moisture levels in timber, but in other materials may register high readings from other conductive materials, not just moisture.
Landlords must make sure their rental homes are safe and healthy for people to live in (see government guidance for landlords). This legal duty comes through the housing health and safety rating system (HHSRS), which is part of the Housing Act 2004. The HHSRS lists 29 hazards in the home. Dampness and mould are listed among the highest categories of hazard.
Do:
inspect the condition of the property at regular intervals
thoroughly and promptly investigate any concerns raised by the tenant, and fix any defects that are causing damp and mould
carry out regular maintenance to keep the property in good condition
ensure appropriate and sufficient insulation and draught proofing are in place
ensure ventilation such as windows, vents and fans are working to the current standards, for example, see Approved Document F for new buildings
ensure tenants know how to use the heating system and thermostatic controls efficiently
use void periods between tenancies to replace any faulty fans or upgrade existing fans with improved trickle-fed humidistat units.
From October 2025, if a tenant reports mould or dampness, registered social landlords (councils and housing associations) must:
(See Awaab’s Law, part of the Social Housing Regulations Act 2023).
One of the most important aspects to consider is occupiers’ health.
In most instances, practical, low-cost measures can solve the problem, e.g. general maintenance of the home and slight changes in the way occupants do things, like closing doors to the bathroom when showering.
However, it is unavoidable that everyday tasks such as cooking, bathing, washing and drying laundry will produce indoor moisture. Many factors are outside of the control of tenants, such as overcrowding or a lack of space to adequately dry clothing. These can be challenging to address and/or require ongoing management.
Do:
listen carefully to what tenants think is causing the problem. It could be that damp and mould only appeared from a particular time, which may mean something has changed, e.g. an escape of water or an increase in the number of residents.
take reasonable steps in partnership with residents. Consider:
Fuel poverty is a significant factor causing low heat levels, and must be considered when discussing and implementing solutions.
Don’t:
assume that you have met your responsibilities. For instance, the mere presence of an extractor fan does not automatically mean the ventilation is satisfactory, without any evidence that the fan is performing to the required standard.
Do:
find out what you have responsibility for. Carefully check your conditions of tenancy, and if you are a leaseholder, check the terms of your lease. Your responsibility to address issues could depend on your situation and occupation rights as a tenant.
report any concerns you have about damp or maintenance issues to your landlord promptly.
If you have HHSRS-related concerns, contact your local council's environmental health team. Your local authority can take action against landlords for non-compliance.
Environment Agency – Risk of flooding
Local council (to find environmental health teams for HHSRS concerns)
Please note that not all firms listed on the ‘Find A Surveyor’ website are RICS-regulated firms.
Find a surveyor in your local area on ricsfirms.com
Check whether your surveyor is regulated by RICS by checking our list of RICS members
Read how RICS regulation helps consumers in our firm regulation consumer guide