Rising damp inside a house

What Causes Damp?

Key Takeaways

Signs of Rising Damp: Damp patches on walls, often starting from the base. Salt deposits (efflorescence) in affected areas. Peeling wallpaper or paint. Musty smell.

Causes of Rising Damp: Absorption by capillarity through porous materials. Lack of or failure in the damp-proof course (DPC). Rising water table or high groundwater levels. Bridging of the DPC by external factors. Porosity of building materials. Cracks and structural defects.

Addressing Damp Problems: Identify and fix underlying issues, such as leaks, poor ventilation, or rising damp. Solutions vary based on the type of dampness and may involve repairs, enhanced ventilation, waterproofing, installing damp-proof courses, dehumidifiers, and insulation.


You might have surely heard of damp – once, twice, or maybe you might have witnessed it in your own house. Well, if you have experienced it, you would also be familiar with that uneasy feeling of living in a home that feels damaged, moist all the time, and does not look attractive at all.

Well, that’s what damp does to your house. It eats the walls from the inside, starts eroding the brickwork, peels all the paintwork, damages the plasterwork, and gives rise to other additional problems such as mould, wet rot, etc.

That’s quite a problem, isn’t it? It is, and things become even scarier when the houseowners are not educated about it. Well, it’s not totally their fault, but still, they must put the effort into knowing what the early signs of a damp problem are and what exactly gives rise to it or, in simpler terms – the cause behind the damp issues.

To make things easier for those who don’t know much about damp, we will talk about it, the signs of it, and what causes it. So, stay with us until the end.


Rising damp on a wall affected by moisture


First, Let’s See the Various Types of Damp

Damp-related structural difficulties can emerge in a variety of ways, demanding a thorough understanding of its various categories for appropriate diagnosis and remediation.

Rising damp, penetrating damp, and condensation are the three basic categories, with each requiring a unique technique for resolution. Let’s see what all these main damp types are precisely:

Rising Damp

Rising damp occurs when moisture from the ground travels upward through porous building materials, such as bricks and mortar, via capillary action. The most common cause is a failure or absence of a damp-proof course (DPC) – a barrier designed to prevent the upward movement of water.

Signs of Rising Damp

  • Damp or discoloured patches on walls, typically starting from the base
  • Salt deposits (efflorescence) in affected areas
  • Peeling wallpaper or paint
  • Musty smell

Penetrating Damp

Penetrating damp occurs when water enters the building from the outside and progresses through walls. Common causes of damp include leaking roofs, defective gutters, cracks in walls, or porous external surfaces.

Signs of Penetrating Damp

  • Horizontal damp patches on walls, often spreading across ceilings
  • Staining or peeling of internal decorations
  • Mould growth
  • Dampness following rainfall


Condensation occurs when warm, moisture-laden air comes into contact with more excellent surfaces, leading to the conversion of water vapour into liquid. It is common in areas with inadequate ventilation and heating.

Signs of Condensation

  • Water droplets on windows and cold surfaces
  • Mold growth, often in corners and on windowsills
  • Musty smell
  • Peeling wallpaper or paint


Peeling of cement and plaster due to dampness


What Exactly Causes Rising Damp?

Rising damp is caused by the ascent of groundwater through porous construction materials such as bricks, mortar, and different masonry elements.

Capillary action—a phenomenon in which water ascends against gravity within restricted spaces, notably the tiny pores and complex tubes inherent in the aforementioned materials—is the primary cause triggering the occurrence of rising damp.

Here’s a more detailed explanation of the factors that cause rising damp:

Absorption by Capillarity

Porous building materials, including bricks and mortar, contain capillaries—small tubes or channels through which water can travel. Groundwater, driven to cold surface by capillary action, is drawn upward into these capillaries.

Lack of Failure of Damp-Proof Course (DPC)

The damp-proof course is a horizontal barrier installed in the walls of a building to prevent moisture from rising. It is typically made of materials like slate, plastic, or bitumen. When a building lacks a DPC or if the existing DPC fails or is compromised, it allows water to move freely through the capillaries, leading to rising damp.


Dark stains and peeling of paintwork on a wall


Rising Water Table or High Groundwater Levels

In areas with high groundwater levels or a rising water table, the pressure of the groundwater against the foundations of external walls of a building can force moisture to move upward through the walls. It is particularly common in buildings located in low-lying or waterlogged areas.

Bridge of the Damp-Proof Course

External factors can sometimes bridge or bypass the damp-proof course. For example, the buildup of soil or debris against the exterior walls or the construction of raised garden beds can create a pathway for moisture to bypass the DPC, exacerbating the risk of rising damp.

Porosity of Building Materials

The porosity of building materials plays a significant role in the development of rising damp. Materials with high porosity, such as soft bricks or mortar with gaps, allow water to be drawn from ground floor upward more easily through capillary action.

Cracks and Structural Defects

Cracks or defects in the structure of a building can provide additional pathways for water to enter. These defects can disrupt the continuity of the damp-proof course, allowing water to move freely through the walls.


Damaged wall due to excess moisture content


What Factors Cause Penetrating Damp?

Penetrating damp is a type of dampness that occurs within buildings as a result of water penetration from the outside environment into the constraints of interior areas.

Unlike rising damp, which has underground roots, penetrating damp occurs when water enters the building, overcoming its defences through numerous channels such as walls, roofs, or other exterior structural components.

Due to this, understanding the complex drivers of penetrating damp is critical for developing a cautious and effective strategy for both diagnosis and repair. A compilation of the numerous causes of penetrating damp in houses includes:

Leaking Roofs

One of the primary causes of penetrating damp is a leaking roof. Damaged or missing roof tiles, cracked flashing, or poorly sealed joints can allow rainwater to penetrate the roof structure and enter the building.

Defective Gutters and Downpipes

Gutters and downpipes are designed to channel rainwater away from the building. When they are damaged, blocked, or improperly installed, water can overflow and run down the exterior and internal walls, leading to penetrating damp.


Peeling paintwork due to dampness on a wall


Cracks in Walls

Structural cracks in the walls provide a direct pathway for water to enter the building. These cracks can result from settling, subsidence, or other structural issues with damp walls, allowing rainwater to penetrate the building envelope.

Porous Building Materials

Some building materials, especially older ones, may become porous over time. Porosity allows water to be absorbed, and during heavy rain, the building may become saturated, leading to dampness.

Faulty Window Seals

Poorly sealed windows or damaged window frames can permit rainwater to enter the building. It is particularly common in older buildings where seals may have deteriorated over time.

Cracked or Damaged Render

External wall rendering on walls can crack or deteriorate, allowing water to penetrate. It is especially true if the render is not properly maintained or if the building experiences significant temperature fluctuations, causing the material to expand and contract.


Fluffy plasterwork due to dampness


Faulty Flashing

Flashing is installed around joints and intersections, such as chimneys, roof valleys, and dormer windows, to prevent water ingress. Damaged or improperly installed flashing can lead to leaks and penetrating damp.

Blocked Cavity Wall Vents

Cavity walls are designed with a gap (cavity) between the inner and outer layers of brickwork. Vents are installed to allow air circulation through internal wall and prevent dampness. When these vents become blocked, the cavity can fill with water during heavy rainfall, causing penetrating damp.

External Defects

External defects in the building’s structure, such as cracks in brickwork or damaged cladding, can allow water to seep into the building.

Poorly Maintained Masonry

Over time, the condition of internal and external walls masonry can deteriorate, especially in the face of weathering. This deterioration can lead to increased permeability and water ingress.


Damaged wall and floor due to rising damp


What Causes Condensation?

Condensation occurs when moisture-laden air meets a surface with temperatures colder than the surrounding air, resulting in the transition of water vapour into liquid form.

This complex phenomenon is caused by air humidity and temperature differentials within a structural building.

Acquiring an advanced knowledge of the numerous factors that contribute to condensation is critical for the precise application of preventative and control techniques.

Humidity Levels

Humidity is a measure of the amount of moisture present in the air. Warm air can hold more moisture than cold air. When warm, humid air comes into contact with a more excellent surface, the air is unable to retain all of its excess moisture, leading to the formation of water droplets.

Temperature Differentials

Condensation is most likely to occur when there is a significant difference in temperature between the warm indoor air and excellent surfaces. Common examples include:

  • Warm, moist air in a bathroom meets the colder surface of a mirror or tile.
  • Warm air inside a building encountering excellent windows or walls during colder weather.

Inadequate Ventilation

Poor ventilation exacerbates condensation issues by allowing moist air to accumulate. Inadequate ventilation is often seen in tightly sealed or poorly ventilated spaces where air circulation is limited, such as in sealed windows, basements, or rooms without proper airflow.

Cooling Surfaces

Surfaces that are cooler than the dew point of the surrounding air are prone to condensation. The dew point is the temperature at which air becomes saturated with moisture, leading to the formation of water droplets. Common cool surfaces include:

  • Windows during cold weather.
  • Cold walls or ceilings in poorly insulated spaces.

Insufficient Heating

Cold surfaces in a building can be a result of insufficient heating. When indoor temperatures are too low, surfaces like windows or walls can fall below the dew point, causing condensation to occur.

Lack of Insulation

Inadequate insulation can lead to temperature variations within a building. Cold spots on walls or ceilings, where insulation is lacking, become prone to condensation when warm, moist air contacts these surfaces.


Efflorescence and dampness on a wall


Need Help with Damp Problems?

Advanced Damp Surveyors Ltd. is one of the best damp surveyors in the United Kingdom. Our local expert will reach out to discuss your issues, provide advice, and suggest permanent solutions.

In the damp survey, we’ll assess condensation, dampness, and mould in your property, measure humidity levels, and identify any underlying problems, offering recommendations for a lasting solution.


What is the main cause of damp in a house?

Damp in a house usually comes from too much moisture getting in. This happens because of things like leaks, poor ventilation, rising damp from the ground, or condensation. If the roof isn’t well-maintained, there are plumbing problems, or the humidity is high, it can also add to the dampness.

How do you get rid of damp?

To eliminate dampness, find and fix the underlying issue. Solutions vary based on the type of dampness and can involve repairing leaks, enhancing ventilation, waterproofing walls, installing damp-proof courses, using dehumidifiers, and ensuring proper insulation. It’s essential to remove the source of moisture and take preventive measures to prevent damp from coming back.

Why is damp coming through walls?

Walls can get damp for different reasons, such as cracks, gaps, or porous materials letting in water. External factors like heavy rain can make it worse. Finding the exact cause is crucial for fixing the problem.

How do you find out where damp is coming from?

To locate the source of dampness, carefully inspect for visible clues like water stains, mold, or peeling paint. Examine roofs, pipes, and windows for leaks. Condensation problems may show as moisture on walls or windows, while rising damp leaves a unique tide mark. For an accurate assessment, consult professionals to identify and address the damp issue.

Table of Contents

Picture of Sam Fitzgerald – CSRT Damp Surveyor

Sam Fitzgerald – CSRT Damp Surveyor

Author – CSRT Damp Surveyor
Sam is a highly qualified and seasoned damp surveyor with over ten years of specialised experience. With a strong academic foundation in building surveying and numerous professional certifications, Sam has established himself as an authority in the field of damp diagnosis and remediation.

At Damp Surveyors Ltd, Sam applies his extensive knowledge to help homeowners across the UK address and solve their damp issues effectively. His approach combines cutting-edge techniques with a commitment to honest, client-focused service, ensuring that every survey and recommendation is tailored to the specific needs of the property.

As a thought leader, Sam’s insights into damp prevention and treatment have been featured in industry publications, underscoring his role as a trusted expert dedicated to maintaining the integrity and comfort of your home.

Testing device for measuring dampness in a house


At Damp Surveyors Ltd, we stand out as your premier choice for damp survey services in the UK. Our commitment to excellence and customer satisfaction sets us apart. Here’s why you should choose us:

  • Exclusive 3 Free Quotes: We offer a one-of-a-kind optional service where you not only get our top-notch damp survey but also receive 3 free quotes from vetted local companies, giving you peace of mind by saving you thousands on getting the most competitive quotes, and also time researching and contacting other reputable companies.
  • Knowledge and Experience: We provide unmatched knowledge to every survey we conduct thanks to our team of seasoned professionals and years of industry experience. This guarantees accurate assessments and practical solutions.
  • Nationwide Coverage: Whether you’re in a bustling city or a rural area, our services extend across the UK, making us accessible wherever your property is located. Choose us for nationwide reliability and excellence.

Choose Damp Surveyors Ltd as your reliable partner for all-inclusive survey needs. Our top concerns are the health and safety of your property, and we are committed to providing outcomes you can trust.

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