Not every moisture problem is immediately visible behind a fresh coat of paint. Whether you have your eye on a charming renovation house in the city or a more recent new construction in the countryside, a sharp eye is always crucial.

Saving tip: Notice any of these things? Then be sure to take pictures of them if you plan to buy your dream home anyway. These are your key pieces of evidence to knock hundreds of euros off the asking price during the price negotiation. After all, a house with damp is worth less, while with the right expertise is often solved faster than you think.

To draw up a budget for your dream home, you do need to know which moisture enemy you are dealing with.

Moisture control is tailor-made. To give you an idea of the budget to provide during your negotiations, we have our specialised moisture solutions including guide prices listed.

Injecting walls against rising damp

When no water barrier is present, groundwater migrates up the walls. The most effective solution is to professionally injecting the walls with a water-repellent gel.

• Target price: From €100 per running metre.

Basement sealing or basement waterproofing

Is the basement of the property you have your eye on damp? At basement waterproofing or caulking, we make the walls and floor completely waterproof with several layers of cementation. This turns the basement back into a usable storage or living space.

• Target price: From €50 per sq m.

Basement drainage

When the groundwater pressure under the house is too high for an ordinary basement pit, basement drainage the only definitive solution. This involves the controlled discharge of water via a pumping system.

• Target price: For a total basement project, expect a starting price from around €2,000.

Concrete injections for leaks

In modern houses or basements made of concrete, hairline cracks or bilge seam problems can cause acute water infiltration. Concrete injection seal these leaks under high pressure.

• Target price: This price strongly depends on the severity of the leak and is customised during our free expertise.

Facade impregnation or hydrofuge

Does the property suffer from penetrating moisture? By the facade impregnation, we apply an invisible, protective layer that repels rainwater while the wall continues to breathe.

• Target price: This can be done from as little as €8 per m².

Ventilation system against condensation and mould

Moisture in the house does not always come from outside. Condensation and mould on the walls often indicate a lack of air ventilation. A professional ventilation system removes polluted, moist air and brings in healthy air.

• Target price: Ventilation solutions start from €1,000.

Plastering and finishing

After moisture control themselves, the walls often need to be repaired. AquaConsult also provides the plastering so your walls will be completely even and paint-ready again after treatment.

• Target price: The price of this depends on the surface area and the condition of the substrate.

How much budget should you provide in total now?

While the exact cost will depend on the severity of the damage and the total area, it is essential to plan a realistic overall budget before purchase to meet moisture control to be able to do so. For an average family home where the ground-floor walls need to be treated against rising damp, combined with a professional finishing of the plastering, you should consider a total budget between €3,500 and €7,000.

If there is also a damp cellar which needs to be fully waterproofed, the total renovation budget rises to between €8,000 and €15,000. By mapping out this total amount, including margin for contingencies, in advance, you will be in a stronger position during negotiations and avoid putting pressure on your renovation budget after purchase.

This typical musty smell, which we often describe as ‘wet dog’ or ‘an old cellar’, does not happen by accident.

So when we talk about this odour, we are actually talking about a complex biological and chemical process that takes place invisibly in the walls and air of your home. To understand how to permanently remove the odour, you need to know what the source of the problem is. This is why science breaks down this characteristic into three crucial factors.

1. Microbial Volatile Organic Compounds (mVOCs)

The smell we describe as musty is referred to in science as mVOCs. These are actually gaseous by-products released during the formation of fungi and bacteria.

From the moment a material such as plaster, wood or insulation becomes damp, it becomes a breeding ground for fungi and bacteria. Microorganisms then literally start eating or digesting the materials. During this digestion process, they emit gases. So what you smell in your home is not the moisture itself, but the chemical emissions from the active moulds that are deep in the pores of your home. Even if you can't see the mould yet, you can already smell it.

2. The role of relative humidity (RH)

The air in your home works like a sponge. Warm air retains more water vapour than cold air. When the relative humidity rises above 60%, the air in the house becomes saturated.

In this saturated state, two things happen:

• Odour retention: Moist air particles or water molecules bind to odour molecules from, for example, cooking, pets or smoke. As a result, these odours linger longer and feel heavier.
• Surface absorption: Excess water vapour in the air finds a way out and condenses on cold surfaces such as the walls or windows. This keeps the process of mould and associated gas emissions (mVOCs) continuously.

3. The ‘chimney effect’ and diffusion

Why do you often smell the musty smell throughout the house, even if the problem is located in the basement? This is because of the laws of thermodynamics. Warm air simply rises. As this air migrates to the upper floors, it creates negative pressure in the lower parts of the house.

This causes moist and mould spore-laden air from the basement to be sucked upwards through cracks, holes in pipes and stairwells. We also call this the chimney effect. This directly affects the air quality in your living room or bedroom by a moisture problem which is located metres below.

A musty smell in your home is rarely the result of a single problem. It is often a combination of environmental factors and the construction of your home.

If the musty smell lingers in the house, chances are it is due to a structural moisture problem that negatively affects air quality day and night. At AquaConsult, we often see our clients smelling the odour but unable to place the source. Therefore, we list the possible culprits.

Rising damp: The constant evaporation

Rising damp occurs when groundwater soaks into the walls through the foundation. This often happens in older houses that have no or damaged flood defences.

• How do you recognise it? Due to wallpaper coming loose, peeling paint or plaster powdering at the bottom of the wall. Sometimes you can also see white salt efflorescence on the wall.
• Impact on air quality: The wall behaves like a large radiator that constantly evaporates clammy moisture into the room. This creates structurally excessive humidity (often above 70%), making the air feel heavy and stuffy.
• The musty smell: The smell is often earthy and clammy, similar to the smell of wet earth or a forest walk after a rain.

Moist basement: The smell factory under your feet

The basement is below ground level and under constant pressure from groundwater. In the absence of a watertight basement forces moisture out and creates a damp cellar.

• How do you recognise it? Puddles of water on the basement floor, clammy walls, a musty smell as soon as the basement door opens or mould on cardboard boxes and wooden shelves.
• Impact on air quality: Through the ‘chimney effect’, cold, humid basement air rises into the rest of the house. As a result, the air quality in your living room or bedroom is directly affected by the polluted air from downstairs.
• The musty smell: The classic, pungent cellar smell. A pungent, mouldy smell that clings to textiles and clothing.

Penetrating moisture or damp walls: The porous barrier

Rainwater penetrates deep into interior walls through a porous façade, cracks in masonry or damaged pointing. When this is the case, we speak of penetrating moisture or damp walls.

• How do you recognise it? Due to moisture spots on the interior wall that get bigger after a heavy rain or an exterior wall that stays dark and wet for an extremely long time after precipitation.
• Impact on air quality: Wet walls lose their insulation value, lowering the indoor temperature and increasing humidity. This creates a cold and unpleasant indoor climate.
• The musty smell: A smell of wet masonry and lime. It is an odour that often comes and goes, depending on weather conditions.

Condensation moisture: The saturated atmosphere

Condensation moisture occurs when warm, moist air cools on cold surfaces due to a lack of ventilation.

• How do you recognise it? The water droplets on the windows, black mould dots in the corners of the ceiling or mirrors that stay fogged up for a long time.
• Impact on air quality: The air becomes saturated and consumed. As the air is not refreshed, mould spores and bacteria accumulate. You literally breathe polluted air.
• The musty smell: The smell is often musty and slightly sour, typical of active fungal growth on organic material such as wallpaper or paint.

Mould on the walls: The active air pollutant

Mold is the direct result of long-term moisture problems. It is a living organism that feeds on your home.

• How do you recognise it? To black, green or white spots and fluffy textures on the walls, ceilings or behind furniture.
• Impact on air quality: Mould continuously emits spores into the air. This drastically lowers air quality and is the biggest culprit for occupants' health.
• The musty smell: A very strong and suffocating odour. It smells like spoiled material and is often the most disturbing smell in the house.

Moisture in new-build homes: The trapped building moisture

Thousands of litres of water are used during the construction process. If this is not allowed to dry out sufficiently before you move in, it will remain the building moisture caught in the construction.

• How do you recognise it? Due to constant clammy air, windows that fog up even with light heating and the house never really feeling warm despite insulation.
• Impact on air quality: It prevents the natural drying of the house and causes excessive humidity from day one, which prevents the growth of the first fungi can encourage.
• The musty smell: A subtle but noticeable smell of damp concrete and stucco that becomes unfresh over time.

Before you open the toolbox, you need to know what causes the moisture problem is. Moisture control is bespoke. Solving one moisture problem is counterproductive for another.

From the moment many people discover a moisture problem, the first question they ask themselves is, “How do I get moisture out of my house as soon as possible?” For different moisture problems, there are different ways to do this. At condensation moisture or building moisture helps intensive ventilation. But beware, because when it comes to a structural problem such as rising damp, then merely opening a window will never solve the root of the moisture problem.

Not every humidity problem requires immediate major intervention. What you can do yourself to bring down humidity in your home:

When moisture problems beyond a fogged-up window, the following mistakes are often made in terms of DIY moisture control.

1. Repaint with anti-humidity paint

This is the biggest and most common mistake when it comes to fighting moisture. Getting rid of a damp wall or mouldy spot with special paint seems quick, but you are locking the moisture in, so to speak. The water seeks another path, often higher up the wall, while the internal structure of your home slowly rots away. You are not addressing the moisture problem, you are covering it up to the naked eye, while it slowly breeds further within the structure of your home.

2. Impregnating the facade incorrectly

The self injecting an external wall or the façade at penetrating moisture is risky. If the façade is not 100% free of cracks, you are again trapping moisture, but behind the protective layer you are applying to the façade. At the first night frost, the water expands and your bricks and joints may simply crack.

3. Installing a false wall against a damp wall

When you don't see it, the moisture problem is already solved for many. This is especially thought to be the case with a damp cellar or room. By installing a plaster wall in front of the moisture problem, you no longer see it, but this way you create a perfect breeding ground behind the wall for unhealthy moulds which you breathe in unnoticed. In the long run, you may experience health problems if you do not solve the moisture problem permanently.

4. Self-injecting walls against rising damp

We often get asked if you rising damp can fight yourself. Indeed, there are do-it-yourself kits you can use to fight your can inject walls, but these are often not powerful enough for thick walls. Without professional equipment, chances are that the barrier will not be fully opaque, so moisture will simply continue to rise in the wall.

5. Failure to distinguish between building moisture and leaks

In new-build houses, moisture spots are often thought to be just construction moisture. As a result, many new owners ignore a real leak or a construction fault, with all the consequences for your new plastering.

When we talk about ‘moisture in your home’, we are usually talking about excess water that settles in the structure of your home or is present in the air you breathe. More than just an aesthetic problem in your home, it affects your home comfort, energy bills and even your health.

But to solve the problem, we first need to know which moisture enemy we are dealing with. What types of moisture are there really?

Damp walls: The common intruder

Damp walls are a collective term for masonry where the building materials are saturated with water. This can occur on both interior and exterior walls.

• What is the cause? It is often a combination of several factors: an outdated façade, minor leaks or faulty ventilation causing moisture to soak deep into the pores of the walls.
• How do you recognise it? With dark, clammy stains on the wallpaper, a musty smell in the room and paint starting to peel off the walls.

Basement moisture: extreme pressure from outside

Moisture in the basement literally means that the basement is no longer watertight. The basement is the lowest point of your home, so it is often the first to be affected by groundwater.

• What is the cause? The main cause is hydrostatic pressure. Groundwater pushes against the basement walls and floor. With cracks or porous walls, water seeps in.
• How do you recognise it? The presence of puddles of water on the floor after rain, white powdery deposits on the walls and extremely high humidity.

Rising damp: The enemy at the bottom of the wall

Rising damp means that groundwater climbs vertically up the walls. It literally draws from the bedrock into your living spaces.

• What is the cause? The lack of a proper water barrier. This makes your wall act like a sponge, soaking up soil moisture.
• How do you recognise it? The damage is limited to the underside of the walls, up to a maximum height of 1 metre. Think loose skirting boards and salt crystals on the bricks.

Permeable moisture: The impact of rainwater

Penetrating moisture is moisture that penetrates horizontally from outside through the façade. This especially after a heavy rainfall.

• What is the cause? A porous exterior wall or damaged grouting. The façade is no longer water repellent and allows water to penetrate into the inner wall.
• How do you recognise it? Due to moisture spots present in the middle of the wall and also darkening after heavy rain. You often see green deposits on the outer wall as well.

Condensation moisture: Living humidity in an insulated house

Condensation moisture arises from daily activities. It is the biggest cause of mould in modern, well-insulated homes.

• What is the cause? A lack of ventilation. Water vapour from cooking, showering or breathing cannot escape and then settles on cold surfaces such as windows and walls.
• How do you recognise it? Fogged windows in the morning, water droplets on windowsills and black mould dots in the corners of the ceiling.

Mould on the walls: The dangerous consequence

Mold on the walls are micro-organisms that are the ultimate evidence of an underlying moisture problem.

• What is the cause? Fungi need moisture and stagnant air to survive. Usually the source is condensation moisture or an untreated leak.
• How do you recognise it? The presence of black, green or grey furry spots and a musty smell that does not disappear by opening a window.

Moisture in new-build homes: Residual building moisture

Moisture in new-build homes is the water left in the building materials of a newly completed house.

• What is the cause? During construction, up to 5,000 litres of water are used for concrete and plaster. If this does not evaporate completely before the inhabitants move in, the moisture will remain trapped.
• How do you recognise it? There is a clammy atmosphere in the house, condensation is present on the windows and the walls dry out extremely slowly after painting.

It can be difficult to pinpoint the exact source of a damp spot. Many symptoms look similar at first glance, but if you look closely, you will see the subtle differences. With these rules of thumb, you will learn the main types of moisture distinguished from each other.

The distinction based on location

• Only at the bottom of the wall? If the damp patches and plaster damage stop at a height of about 80 cm to 1 metre, chances are 99% you are dealing with rising damp.
• Scattered all over the wall or in the corners? When spots are also higher on the wall or concentrated in the upper corners of a room, this usually indicates condensation moisture or penetrating moisture.

The distinction based on the moisture stain itself

• Black spots and fungus? Do you see small, black dots expanding? This is a typical feature of condensation moisture. Mould grows on walls, after all due to a lack of ventilation.
• White crystals or powder? Do you see white, salty rash on the bricks or plaster? This indicates rising damp or moisture in the basement, leaving minerals from the groundwater behind in the wall.

The distinction based on weather conditions

• Does it get worse after rain? If the stains on your wall darken or expand immediately after a rain shower, you are dealing with penetrating moisture. The moisture then penetrates from outside to inside.
• No link to the rain? If the spots are constant, then condensation moisture or a structural problem such as rising damp the culprit.

Tip: The 'Aluminium foil test'

Do you hesitate between penetrating moisture or condensation moisture? Then stick a piece of aluminium foil on the damp wall and let it sit for 48 hours.

• Moisture on the outside of the film? Then it condensation moisture. The moisture from the air in the room settles on the cold foil.
• Moisture behind the foil? Then the moisture comes from the wall itself, indicating resounding or rising damp.

Note: While these checks give you a good indication, moisture is often an insidious problem. Sometimes multiple causes are present at the same time. For watertight assurance a professional moisture measurement by an AquaConsult expert is always the safest choice.

Before investing in expensive renovation materials, check the foundations of your home. A moisture problem is not always immediately visible on the walls, but there are clear signs you can look out for during your renovation to identify the problem:

Note: Sometimes a wall may appear dry on the surface, but the moisture may also be deep within the structure of your renovation project. At AquaConsult, we recommend that when renovating, you should always a free expertise to be carried out where the damp is diagnosed. Our experts measure the walls with professional equipment, so you can be sure you can start renovating or already decorating with confidence.

During a renovation, you can use different types of moisture problems face. Each problem is unique and requires a specific recognition and approach.

Moisture in the walls

Moisture in the walls is a wider problem for walls saturated with moisture, often due to the combination of factors such as leaking pipes or old construction defects.

How do you recognise it? Due to dark, clammy stains present on the walls that do not seem to dry up, regardless of the weather. Sometimes the stucco feels soft or powdery when you push against it.

Damp basement

The basement is under constant pressure from the surrounding groundwater. During renovation, it is therefore the ideal time to make this space usable again and from the damp cellar make a valuable repository.

How do you recognise it? There are puddles of water present on the basement floor after a rainstorm, the walls shining with moisture or salt standing as a white haze on the basement walls.

Rising damp

Rising damp is one of the most persistent moisture problems, especially in older houses where a water barrier is missing. Groundwater then soaks up inside walls like a sponge.

How do you recognise it? Damp patches, loosening plaster or flaking paint limited to the bottom of the walls (up to 1.20 metres high). You often see a clear horizontal flood line on the walls.

Penetrating moisture

At penetrating moisture rain and wind penetrate through the external wall, often because the façade has become porous or cracks are present in the pointing.

How do you recognise it? The presence of moisture stains that are higher up on the wall and often get bigger after a heavy rain indicate the presence of penetrating moisture. The spots are usually on the rain-side of your home.

Condensation moisture

Condensation moisture occurs when warm, moist air precipitates on cold surfaces in the house. In renovations, we often see this after installing new windows and insulation, as natural ventilation is then lost.

How do you recognise it? Drops on the inside of windows, moisture spots in the upper corners of rooms or on ceilings and a typical musty smell in the house.

Mould on the walls

Mould on the walls is not itself a moisture problem, but it is the direct result of an untreated moisture problem or lack of ventilation in the house. It is not only aesthetically disturbing, but more importantly, it is unhealthy for the inhabitants.

How do you recognise it? You see black, grey or green speckles on the walls. Usually in the corners, behind cupboards or around window mouldings. It is almost always accompanied by a recognisable mouldy smell.

Moisture in new-build homes

No, moisture is not only a problem when renovating an older home. Even in recent renovated homes, moisture can be a killjoy. During construction, a huge amount of water is used for concrete and plastering. The excess water is then trapped in the foundations and construction of the house.

How do you recognise it? Windows that constantly fog up and plaster that still shows dark spots after months or that won't budge. If you start painting too soon, the paint will not adhere and will therefore peel off.

At AquaConsult, we don't believe in a temporary patch-up. A renovation deserves a structural moisture solution.

Wall injection: an impenetrable barrier

At wall injection we drill small holes in the affected walls at regular intervals, just above the floor pass. Into these holes, we inject a high-quality, moisture-resistant gel or liquid under controlled pressure. This product spreads into the masonry and, once cured, forms a horizontal barrier that no longer allows a drop of water to pass through. This is used for rising damp to efficiently get the walls cork dry so that they no longer soak up groundwater.

Basement sealing: a waterproof tub

At basement waterproofing we make the basement walls completely waterproof again by applying several layers of cementitious fixing mortars and synthetic resin. We create a new, waterproof shell on the inside of your basement. The critical connection between the floor and the wall is also additionally strengthened in the process. This is used for damp cellars and moisture in the walls. It is ideal for turning a damp storage room into a full-fledged hobby room or wine cellar.

Basement drainage: controlled water drainage

Sometimes the pressure of groundwater is so great that casing is not sufficient. In that case, we place a drainage system on the floor or against the walls. A special studded membrane catches the water seeping in and directs it through channels to a collection point, where a pump automatically drains the water to the sewerage system. The walls are then finished tightly. This is used for stubborn damp cellars with very high groundwater pressure, where pressure must be removed.

Facade impregnation: Giving your property a mackintosh

At facade impregnation we spray a colourless, water-repellent liquid over your facade. This liquid soaks deep into the pores of the brick. The result? Rainwater beads off the façade, while the wall itself can still breathe. This way, any internal moisture can still evaporate to the outside. This is used for leaking moisture. It protects the facade not only from moisture, but also from frost damage and pollution.

Mechanical ventilation: The lungs of your home

We install smart ventilation systems which constantly monitors the humidity in the house. As soon as the air becomes too humid, the system drains the polluted air and brings in fresh, dry air. This is used for condensation moisture and mould on the walls. Ventilation systems are indispensable in any renovation where insulation levels are increased.

Concrete injection: sealing active leaks

Sometimes water seeps in through shrinkage cracks or gravel nests in concrete structures. At concrete injection we drill holes at a 45-degree angle across the crack and insert special injection packers. Under high pressure, we inject a polyurethane resin that immediately expands as soon as it comes into contact with water. The crack is thus completely and permanently sealed from the inside out. This is used for damp cellars or moisture in the walls, where there is active water seepage through cracks in the concrete walls or floor slabs.

Plastering: The salt-resistant finish

After moisture treatment, we install a salt-resistant membrane or use sanitising mortars, followed by a new, tight plaster. This prevents residual salts from the wall from damaging your new finish. This is used in any solution to any moisture problem to ensure a lasting beautiful result.

Because every renovation project is bespoke, the cost depends on the severity of the damage and the technique. Just remember that moisture control significantly increases the value of your property and prevents further damage to the structure.

Figures show that as many as 1 in 4 Flemish homes is struggling with damp cellar walls. Especially with high groundwater pressure, traditional methods such as basement waterproofing often fall short. The result? Walls that remain damp to the touch, with all its consequences.

Damp basement walls not only cause visible damage, but can also cause mould growth, odour nuisance and even structural problems. Especially if you use the basement for storage or as a technical room, it is essential to addressing moisture problems at the source.

Basement waterproofing is a classic method where a cement layer is applied to the walls. This approach can keep moisture out temporarily, but in case of permanent water pressure or rising groundwater, damp basement walls are inevitable. An alternative approach then becomes necessary.

There are three main scenarios:

In all cases, it is crucial not to ignore damp basement walls but to tackle them purposefully.

In floor drainage, a drainage system is placed on top of the existing floor, which actively drains incoming water. The system was optimised by engineer Eddy Peeters of AquaConsult. Instead of concrete and bubble membrane, he opted for a ceramic tile floor with a flexible joint that does not come loose. Not even with prolonged exposure to damp basement walls.