- Project plans
- Project activities
- Legislation and standards
- Industry context
- Specialist wikis
Last edited 29 Sep 2020
Mould growth in buildings
Mould (sometimes referred to as mildew) is a fungal growth. Whilst mould itself is not toxic, some moulds can produce toxins that can have negative effects on human health, for example causing asthma, rhinitis, itchy eyes, respiratory symptoms, respiratory infection and eczema.
Mould spores are microscopic (ranging from 3 to 40 microns) and ubiquitous in the environment. Mould spores can be found floating in the air and in normal house dust. It is not generally practical therefore to eliminate mould spores and this is not a strategy for controlling mould growth.
Mould will feed on any substance that contains carbon atoms (such as organic substances). Many of the natural materials found in the built environment provide suitable food for mould, such as timber and paper. Removing sources of food for mould from an environment is generally impractical.
 Appropriate temperature
The majority of moulds grow well in a range of temperatures similar to those that humans require. This temperature range is wide, and even temperatures close to freezing will not prevent growth. In warmer environments, moulds will thrive. It is generally impractical therefore to control mould growth through temperature.
Most moulds require relatively high levels of moisture in order to grow. The majority require an equivalent of at least 70% relative humidity to thrive and most large mould outbreaks in buildings, occur where porous, cellulose-type materials contain persistent liquid water or condensation.
- Natural or mechanical ventilation.
- Use of de-humidifiers or air conditioning units.
- Insulation of cold surfaces, such as pipes.
- Increasing air temperature.
- Removing sources of moisture such as drying clothes and ensuring vented tumble dryers are appropriately vented to the outside.
- Mending leaking pipes, wastes and overflows.
- Eliminating rising damp and penetrating damp.
 Related articles on Designing Buildings Wiki.
- Approved Document C.
- Cracking and building movement.
- Damp and timber report.
- Damp proofing.
- Defects in brickwork.
- Defects in stonework.
- Degradation of construction materials.
- Dry rot fungus.
- Penetrating damp.
- Recognising wood rot and insect damage in buildings.
- Rising damp.
- Rising damp in walls - diagnosis and treatment (DG 245).
- Thermal bridge.
- Wet rot.
 External references
Featured articles and news
BG 50 & VDI 2035 – your questions answered.
Will the way we heat homes change when winter comes ?
Can XR technology be leveraged in design & construction?
Or are you capping.
Digital gaming competition for UK students aged 16 to 18.
Heritage protection in England vs Australia.
Three-quarters of fire doors fail inspections
The role of geoparks, biospheres and world heritage sites.
Just one month to go ! Find out more here.
A new gallery for the University of Huddersfield.
What will it take to stop it ?
To celebrate world bee day 2022 !
Not forgetting part F and the new part overheating part O.
As energy prices jump up in cost.
With people in the UK from Ukraine.
Industry leader Steve Murray takes on role.
An abundant and versatile building material.
600,000 heat pump installations targeted per year by 2028.
Helping prevent those unwanted outcomes.
How has transport changed due to Covid-19 ?
Will you need it ? after June 15 and the new Part O ?