Top 5 Causes of Damp in Commercial Buildings (and How to Spot Them)
Damp is one of the most common problems found in commercial buildings. Left untreated, it can damage the structure, reduce indoor air quality, and create an unhealthy environment for occupants. Often, damp develops gradually and goes unnoticed until it’s already causing significant issues.
Here are the top five causes of damp in commercial properties — and the early warning signs to look out for.
1. Roof Defects and Rainwater Ingress
The problem: Flat roofs, pitched roofs, and ageing coverings are all vulnerable to leaks. Blocked gutters or broken downpipes can also push water back into the building.
Warning signs:
Staining on ceilings or upper walls
Flaking paint near rooflines
Drips during heavy rain
Tip: Schedule regular roof and gutter inspections, particularly after storms.
2. Penetrating Damp Through Walls and Windows
The problem: Cracked masonry, deteriorated pointing, porous stonework, or failed sealant around windows and doors allow rainwater to pass through walls.
Warning signs:
Damp patches that worsen after rainfall
Black mould near windows
Bubbling plaster or paintwork
Tip: Check for gaps in mortar and reseal window perimeters before they become a problem.
3. Condensation and Poor Ventilation
The problem: High occupancy, kitchens, and bathrooms all produce humidity. Without adequate ventilation, warm moist air condenses on cold surfaces.
Warning signs:
Mould on ceilings, corners, or behind furniture
Streaming windows
Musty odours in enclosed spaces
Tip: Improve airflow with mechanical extraction or trickle vents, and manage indoor humidity.
4. Rising Damp from Ground Level
The problem: Older buildings may lack a damp-proof course (DPC), or have one that has failed. This allows ground moisture to rise into walls by capillary action.
Warning signs:
Tide marks or staining along ground floor walls
Rotten skirting boards
Powdery plaster at low level
Tip: A damp survey can confirm rising damp and recommend solutions such as DPC injection or improved drainage.
5. Plumbing and Internal Leaks
The problem: Leaks from toilets, sinks, kitchens, or heating pipes often remain hidden until damage becomes obvious. Even small leaks can create serious damp patches.
Warning signs:
Localised damp that doesn’t match external weather
Unexplained drops in water pressure
Dampness around service risers or ducts
Tip: Keep plumbing systems maintained and investigate unusual damp spots without delay.
Why Professional Damp Surveys Matter
Different types of damp often look the same to the untrained eye. Misdiagnosis can lead to unnecessary costs and failed repairs. A targeted damp survey uses specialist tools and proven methods to identify the root cause, ensuring the correct remedial action is taken.
👉 Arrange a professional damp survey today to pinpoint the source of damp and protect your building.
FAQs About Damp in Commercial Buildings
Is damp dangerous?
Yes. Damp can encourage mould growth, which may trigger respiratory issues, allergies, and other health problems for building users. Long-term exposure can also damage building materials, weakening structures and finishes.
Can damp lower property value?
Definitely. Evidence of damp is a red flag for buyers, tenants, and lenders. It can reduce rental yields, increase repair costs, and make refinancing more difficult.
How do I know if my building has damp?
Look for signs such as peeling paint, mould, staining, musty smells, or cold walls. However, many issues are hidden within walls, ceilings, or floors — which is why professional surveys are important.
What’s the difference between rising damp and condensation?
Rising damp occurs when moisture travels upwards from the ground through walls, while condensation happens when warm, moist air settles on cold surfaces. They look similar, but require very different solutions.
When should I arrange a damp survey?
If you notice any signs of damp, suspect water ingress, or are buying or leasing a property, it’s wise to get a survey done. Acting early reduces long-term costs and disruption.
Would you like me to draft the next blog post in the series (“Why Penetrating Damp Around Windows is More Common Than You Think”) in the same style with an FAQ at the end?