Dampness in Homes: Causes, Prevention, and Effective Solutions for a Dry and Healthy Living Space

All houses, whatever their age, contain moisture. It will be present in the building materials used and the air within the home. The natural tendency of moisture is to spread out from wet to dry areas, and also to move downwards under the influence of gravity, and your house construction should allow for this.

Simply put, dampness is just a localised excess of naturally occurring moisture. The excess is always caused by one of two things:

• Either a sudden increase in the amount of moisture entering the building;
• Or a gradual local build-up of moisture caused by its inability to escape.

Dampness caused by a local build-up of moisture is often given a variety of names depending on where it shows up, such as ‘penetrating damp’ and ‘rising damp’. These names are both misleading and largely meaningless — the problem is almost always an excess of trapped moisture.

Unlike modern buildings, the construction of an older house is designed to prevent damp problems by preventing the excess build-up of moisture.

They were built almost entirely of permeable, with virtually no attempt at waterproofing materials in the modern sense, and so moisture will pass freely through the walls, floors and ceilings. Instead of being sealed into rooms as condensation, moisture inside the house is able to pass from room to room, and also pass through the external walls to the outside air.

Historically, most dampness was caused by the lack of maintenance leading to leaks. Nowadays, the majority of cases of damp in period houses are caused by inappropriate building work that stops moisture escaping.

With older solid walls it’s advisable to remove incompatible modern materials such as cement render or mortar pointing that trap damp. Replace with traditional lime-based breathable materials that allow moisture to evaporate. Allow time for walls to dry out and keep the house heated.

Dampness which is caused by any sudden increase in the amount of moisture entering the building usually appears without warning — and in a matter of hours. It can also disappear just as quickly in the early days.

The dampness associated with this type of problem is usually very well defined, as it is concentrated and intense. The cause of the problem is often fairly obvious too.

Any tiny drips from plumbing can be the cause of a large and intense damp patch — the escape of water may be small, but is often regular and concentrated on the same spot. This focused, repeated wetting quickly introduces more moisture than can escape, and the overload then spills into neighbouring areas. Hairline cracks in the grouting to bathroom wall tiles, when combined with ‘power showers’ can also be a recipe for damp in homes.

Check for:

●     corroded water pipes concealed in the walls

●     new plumbing for central heating, kitchens and bathrooms which drips when first used

●     Tile in terrace

●     Punning in walls

●     Washroom condition

Less Obvious Causes of Dampness

The cause of the damp is not always obvious, and there may be multiple defects that are all contributing to the cause. Although modern building work is often the primary cause of damp problems, there can be a delay of years before the dampness becomes noticeable, so the link isn’t always obvious.

If a wall is damp, the solvents never completely dry out and the chemicals never cure; the process will just saturate the wall with even more water.

The walls may be replastered with a waterproof cement plaster to try and hide any damp for the duration of the guarantee. This stops the natural movement of moisture — making any damp problems worse.

Used on the exterior of walls, this sort of coating develops cracks all over its surface. The size of the cracks depends on the quality of the render and skill of the builder, but they’re impossible to prevent. The cracks encourage water into the wall, but the water cannot escape because the render is impermeable.

Even if cement render is not yet visibly cracked, it encourages condensation to form as moisture from inside the house can no longer escape — this process can even result in clay lump walls collapsing.

It is important that any excess moisture from below the floors can pass up through the floor and harmlessly into the air. If a floor is replaced with a modern solid design that prevents this from happening, moisture is forced to travel under the floor into the adjoining walls to escape. This will increase the overall amount of moisture in the base of the walls and potentially make those walls damp.

If the outside ground levels are correct and nothing on the outside of the walls prevents the moisture from escaping into the air, you may find only the internal walls are badly affected by the modern floor.

This too is relatively impermeable and so prevents moisture passing through. It may just form a thin layer over the original plaster, but in the worst cases, all of the original plaster will have been removed and replaced with waterproof cement render covered with a thin layer of pink plaster.

Used directly on solid walls (inside or outside in the case of paint), these too are mostly impermeable and prevent moisture moving through the walls and escaping.

Cement mortars not only stop moisture moving freely through the wall and escaping into the air, but they also encourage water into the wall through cracks that always form in cement. These mortars also force natural salts to crystallize in brickwork, causing the bricks to break up.

Most below-ground rooms were cellars and cold stores which were an important part of the moisture control system. True cellar stores have their walls in contact with the ground and allow moisture to saturate them — ensuring they remain cool.

They are often built to intercept underground watercourses, and may have regularly flooded to a few inches. As nothing was stored on the floor or in direct contact with the walls, water and damp did not matter, and the flood water was used to save going outside to a frozen well or pump in winter.

Good ventilation allowed excess moisture to escape. If the cellars ever get converted into habitable rooms, the ventilation is stopped up — forcing moisture up into the rooms above.

This is almost guaranteed to be a problem. As a general rule, houses were always raised up above their surroundings. If the house was built with a brick paved ground floor, at the very least, this was laid on top of the existing ground level with a layer of fine ash or sand beneath to give a level finish.

Nowadays, you can often see old steps that once led up to doors, partially buried beneath later paving. It is also common to see door thresholds that were originally above a top step, now below the adjoining ground so you step down to them.

External ground levels should be at least 200mm below floor level, so it is important to ensure that earth is not banked up against outside walls. Patios are often laid too high, causing bridging of DPSc or rain splashing on hard surfaces saturating the walls. Installing a shallow gravel-filled trench around the base of the wall assists evaporation of moisture.

Formerly damp plaster can retain a residue of salts deposited by the water. Sometimes when rooms are heated after being left empty, dampness can reappear on the surface of the paster because these salts absorb moisture from the atmosphere of the room. Salts should be brushed or vacuumed off.

Preventing Dampness in Modern Homes

While older homes were built with breathability in mind, modern construction often prioritizes airtightness, which can sometimes lead to damp issues. To prevent dampness in new homes, consider the following strategies:

1. Ensure Proper Ventilation

• Install extractor fans in kitchens and bathrooms to reduce condensation buildup.
• Keep windows open for a few minutes daily to allow fresh air circulation.
• Use dehumidifiers in rooms prone to excess moisture.

2. Maintain Gutters and Drainage Systems

• Regularly clean and inspect gutters to prevent blockages.
• Ensure that downpipes direct water away from the building foundation.
• Fix any leaks in the roof or around windows to avoid water ingress.

3. Use Breathable Building Materials

• Opt for lime-based plaster and paints that allow walls to breathe.
• Avoid non-permeable cement renders that trap moisture.
• Consider using wooden flooring instead of impermeable vinyl or tiles.

4. Check and Maintain Plumbing Regularly

• Inspect pipes for leaks, especially in concealed areas.
• Repair minor plumbing issues before they cause extensive damp problems.
• Ensure bathrooms and kitchens are properly sealed to prevent water seepage.

5. Keep External Ground Levels in Check

• Maintain a gap of at least 200mm between ground level and internal floors.
• Ensure proper drainage around the house to prevent water accumulation.
• Avoid high patios or raised flower beds that may trap moisture against walls.

By proactively addressing these factors, homeowners can significantly reduce the risk of dampness, ensuring a healthier and more comfortable living environment.

Conclusion

Dampness in homes is a widespread issue, but with the right understanding and preventive measures, it can be effectively managed. Whether you live in an old house with breathable walls or a modern building with airtight construction, proper ventilation, regular maintenance, and the use of suitable materials are key to keeping dampness at bay. By addressing moisture at its source and allowing natural evaporation, you can protect your home from structural damage and maintain a healthier indoor environment. Implement these strategies today to ensure your home remains dry, comfortable, and free from damp-related issues.

FAQs on Dampness

1. What are the first signs of damp in a house?

Common signs include musty odors, peeling paint, damp patches on walls, mold growth, and condensation on windows.

2. How can I prevent dampness in my home?

Ensure good ventilation, fix leaks promptly, use breathable building materials, and maintain proper drainage around your home.

3. Does dampness affect health?

Yes, damp and mold can lead to respiratory issues, allergies, and other health problems, especially for children and the elderly.

4. Can dampness cause structural damage?

Yes, prolonged dampness can weaken walls, ceilings, and floors, leading to costly repairs and potential safety hazards.

5. Is a dehumidifier effective in reducing damp?

Dehumidifiers help control moisture levels but should be used alongside proper ventilation and leak prevention for the best results.

6. What is the best way to treat rising damp?

Removing non-breathable materials, improving drainage, and using lime-based plasters can help manage rising damp effectively.

7. Why do modern homes experience more damp problems than old houses?

Modern homes are often built with airtight materials that trap moisture, whereas older homes allow natural airflow, preventing damp buildup.