No matter the age of a property damp and mould can be a real problem and it is a common problem in both rented accommodation as well as privately owned properties. It is really important that both landlords and tenants understand what causes damp and mould and what can be done to prevent it or, if it is already present, how to get rid of it and stop it coming back. In this guide we will take a look at the causes of damp and mould and give useful hints and tips on prevention and cure, but we will also touch upon how serious an issue mould can be and why it is important to deal with it quickly.
What causes mould?
Mould in a property is caused by damp. It’s that simple. When water comes into contact with things like paint or wallpaper it creates a perfect growing ground for mould. So, how does mould grow? That perfect mixture of food from the organic content of the paint or wallpaper along with the moisture and the perfect temperature we all tend to have in our properties (between 15°C and 25°C) is absolutely perfect for the mould spores which can enter the home anytime a window or door is opened. Once the mould comes in contact with the damp area and it has food and is at the right temperature, it will simply feed and grow as any living organism will.
What causes damp?
Damp inside a house can be caused in two main ways: penetration through the fabric of the property or condensation. Let’s look at these types of damp in more detail:
Condensation
Condensation in a property is caused any time warm water is released into the air from daily activities which then hits a colder surface such as a window, door, external wall or a ceiling. This warm water can come from simple things like taking a bath or a shower, washing up, drying clothes on a clothes horse or radiators or even boiling a kettle or cooking. All of these activities heat the water up to the point that water vapour is created in the air. When this warm water comes into contact with the cold surfaces it condenses back to water and creates the damp. Things like a lack of ventilation or poor insulation will make condensation a big problem.
Building fabric
Water can penetrate into the property from outside several ways:
- Rising damp – this is where there is either no damp proof course at all or it has failed. In this case, ground water can rise up past where the damp proof course would be and seep into the home
- Penetrating damp is caused when it rains but when there are cracks in brickwork or there are missing tiles on the roof. This can also be caused by blocked guttering which allows water to spill over from the gutters and soak the walls and also leaks in any plumbing either externally or within the wall.
Types of Mould
There are many types of mould that can grow inside a property but quite often people will only refer to white mould or black mould as that is what the mould looks like visually. It is, however, not correct that these are caused by one single mould variety. For a detailed view on the various types of mould take a look at this great article from Water Treatment services on the different types of mould. In this guide we will only take a brief look at a few of the more common types:
Black Mould
Black mould is most often caused by the Stachybotrys fungus which is typically black or very dark green and slimy to the touch. It is very common in areas with a high humidity most of the time like bathrooms and it loves to grow on things like wood, paper and wicker furniture.
White Mould
White mould is, again, potentially caused by several different strains of fungus, but the most common is Aspergillus. Aspergillus thrives in similar environments to Stachybotrys but is very common in cellars. Quite often this white mould is confused with Efflorescence which is the perfectly harmless leaching of salts out of bricks which can stain them white. A simple test is to spray the white stain with water, if it dissolves it is almost certainly efflorescence.
Is Mould dangerous?
So, can mould make you sick? Yes, it can. Mould is classed in 3 main categories:
- Allergenic, which is where the mould causes an allergic reaction in people who are sensitive to it.
- Pathogenic which is where the mould can cause health problems in people who have underlying health conditions, but which tend to be relatively harmless to those who are perfectly healthy
- Toxigenic, which is where the mould can cause serious or life-threatening health problems.
Black mould is classed as a toxigenic fungus, meaning that it can lead to serious or life-threatening health conditions as it produces mycotoxins. Stachybotrys is particularly bad for young children and babies. Aspergillus, or white mould, tends to be much milder for healthy individuals but can cause Aspergilliosis in those who already suffer from lung conditions such as asthma or have a weakened immune system.
As the fungi tend to cause problems with the lungs it can be easy to miss the fact that it is the mould causing any ill health, so what are black mould symptoms and general mould allergy symptoms?
If the mould causes health issues with the lungs, then the following symptoms might occur:
- shortness of breath
- a cough – you may cough up blood or lumps of mucus
- wheezing (a whistling sound when breathing)
- a high temperature of 38C or above
- weight loss
- Headaches or migraines
- Nausea
For exposure causing an allergic reaction the following symptoms are common:
- Runny nose
- Congestion
- Sneezing
- Coughing
- Sore throat
- Irritated eyes
- Skin rashes and itching
How to diagnose damp
There are a few simple ways to know if you have damp in your home. At the most technical level, you can get hold of a moisture meter and test certain areas such as walls or woodwork, but it is simpler than that. Quite often you can smell damp, so what does damp smell like? Ever been in a property and it has a musty or earthy smell? That is damp and mould. Other signs are things like peeling paint or wallpaper or dark stains on walls or ceilings. If you can see or smell any signs of damp then it will need sorting as the mould isn’t too far away. One thing that worries people when they have damp and their home has that odour is how to get rid of the damp smell. The only real way is to sort the damp issue permanently, thoroughly clean or remove the mouldy areas and then ventilate the property well. Sometimes this might not work as the smell has permeated into soft furnishings or carpets and, unfortunately, the only way to sort that is to remove the item and replace it.
How to get rid of Damp
By far the simplest way to avoid mould is to avoid those damp conditions that the mould thrives in. It is much harder to get rid of the spores or even the food that the mould loves. It doesn’t make any real difference if it is damp on walls, damp on ceilings or rising damp, preventing the inside of your home being damp is key.
How to Stop damp coming through walls
If the problem with damp is caused by the water coming through the fabric of the building, then the first thing that is needed is a survey to see where the water is coming in. Checking the gutters is easy and when it rains it is easy to spot if the gutter is overflowing or leaking through the joints. Either way, the gutter will need unblocking or the joints fixing, which is a relatively easy job. If the issue is with the condition of the outer walls such as cracks or poor mortar, loose flashing or missing tiles, then it is likely a builder will be needed to sort those issues out.
What about rising damp though? This isn’t typically an issue in newer houses where damp proof membranes form part of building regulations, but it can happen. Depending on the age of the property, this can be a very specialist task as modern remedies such as injecting a chemical damp proof treatment do not work for older houses. We would always recommend bringing is a specialist surveyor to assess the situation and make recommendations, but some potential remedies are:
- Try to relandscape externally so that the external floor height is 15cm below the internal floor height
- Replace the lower levels of plaster with breathable lime plaster or a hydraulic lime plaster and apply a vapour permeable paint
- Remove any cement based pointing and reapply a lime based mortar
Lime based plasters and mortars are breathable, which is vital to the property but they do not allow moisture through.
Preventing condensation
If the damp is coming from condensation in the home, then good condensation management is needed. There are a few things to do to reduce condensation:
- Try to keep the internal temperature reasonably constant. Turning the heating on and off will only cause water to evaporate more and then condense on the cold surfaces once it cools down
- Avoid drying clothes indoors, but if you have to, try to use a dehumidifier in the room where they are being dried. This is will not only remove water from the air but speed up the drying process
- Ensure that kitchens and bathrooms are properly ventilated with either a working extraction fan or opening windows when cooking or washing.
- Cover pots and pans when cooking to prevent water being lost from them
- Do not block air bricks into the property, these provide ventilation which is key to avoiding condensation
- Ensure that the walls and loft space are properly insulated. Particularly on north facing external walls which tend to be the coldest, proper insulation is perhaps key on how to get rid of damp on walls.
- Clean up any condensation quickly and don’t allow it to build up.
If there is damp in the property you are probably wondering how to dry out damp walls fast or how to treat damp walls before painting.
When looking to dry walls or any other surfaces for that matter, the first thing is to ensure that the problem causing the damp has been fixed. Once it has been fixed then you will need to ventilate the room well. Airflow is key to remove the moisture. So open windows and use fans to move air around and allow the surfaces to dry out. For larger areas try using a room dehumidifier or a portable air conditioning unit (Don’t open the windows if you are using either a dehumidifier or aircon unit as all you’ll do is dry out the outside air). Turn on the heating in the room to create some warmth. This process might take some time so be patient.
How to treat damp walls before painting
Before painting any previously damp walls there is some prep work that will be needed. You cannot simply paint over damp spots as this will just fail with time. Just follow these simple steps:
- Remove the damp or mould stains (more on this later)
- Use a good quality plaster patch or waterproof sealant to repair the plaster
- Apply a waterproof seal paint to the new area of plaster and around it
- Once everything has dried then paint the area with a good quality paint. It might pay to use a specific damp and mould resistant paint.
How to get rid of mould
If mould has grown on a surface, then it needs to be removed and there are different ways to get rid of the mould depending on where it is.
How to get rid of mould on walls
Mould on walls is perhaps the most common issue to deal with in a property and when looking at how to remove mould from walls, it is important to deal with the root of the issue not just the surface mould. As previously mentioned, the first step is to deal with the damp issue. There is no point getting rid of any mould if the damp has not been dealt with as it will only come back.
If the area with the mould on has been wallpapered, then it will make sense to strip the wallpaper off as there will be mould behind it which needs sorting. The same goes if the wall is painted, you will need to try and scrape the paint off or sand that area to get back to the plaster. Once the area is ready, use a mould or mildew remover with a coarse sponge to properly treat the area. We would always recommend having windows open, wearing a face mask and gloves and keeping children and pets out of the room when doing this. Permagard have a great mould remover kit available for sale. You might also want to consider wearing some disposable clothes too.
For plasterboard walls, the most effective way, though, is to cut out the affected area and replace it completely as mould will permeate into the plasterboard and simple surface washing will not treat the problem. When looking at how to get rid of mould on a ceiling, exactly the same process needs to be followed. As you are working above head height we would, however, recommend wearing eye and face protection to protect you from splashes.
How to get rid of mould in bathroom
As with all mould treatment, the first thing is to ensure that the cause of the damp and mould is sorted. In a bathroom, the issue is mostly condensation so ensure that the bathroom has got good ventilation and that this is used when bathing or running hot water. Always ensure that any extractor runs on for at least 10 minutes after you have finished in the bathroom as there will still be moisture in the air which needs removing. There are typically 3 areas where mould will grow: on painted ceilings and walls, on the grout between tiles and on shower, bath or sink sealant.
Getting rid of mould on bathroom ceilings and walls
This is no different to any other wall or ceiling really and the same steps should be taken. When the mould has been properly removed, it is best to re-paint, if that is what you are doing with a specialist damp seal paint and then a mould resistant paint specifically formulated for bathrooms and kitchens such as this specialist paint from Ronseal.
Getting rid of mould from grout
The most permanent way of doing this is to cut the grout out and replace it with mould resistant grout. Alternatively use a mould removal spray such as this one from Ronseal, leave it to work and then scrub with a stiff brush and wash off. You might find, though, that there is a residual staining to the grout, especially if the grout is white, which you might not like.
How to remove mould from sealant
Once again, the most robust way is to cut out the sealant completely, give the area a thorough clean with mould remover and then re-apply a mould resistant silicone sealant. Although you can use a borax solution or bleach to kill the mould and clean it, once stained, sealant is very hard to get pure white again so removal and replacement is perhaps the best course of action.
How to stop mould coming back
Treat the damp problem first and foremost. If this isn’t treated and the property remains damp then mould will always come back. Thoroughly clean or remove and replace any areas or items affected to remove all mould spores and growth. Treat the area with mould resistant paints and sealants and then finally make sure that the damp does not come back. Fundamentally if the property is not damp, the mould won’t come back.
How much does damp devalue a house?
Perhaps one final consideration when there is a mould or a damp problem and this is much less serious than the obvious health issues is the effect that damp and mould have on a property’s value.
Most people would not consider buying a property with a serious damp issue or that musty smell but there are folk out there who would make the improvements and who would consider buying the property. This does come at a price though and most of these people would not pay full asking price as they would need to spend money to fix the problem. For simple damp issues in an otherwise habitable property the issue will typically devalue the property by 10-20%. It is important to note, that if you are aware of the damp issue, it is a legal requirement to notify any potential buyers of the issue. You cannot try to hide it and not mention it as there are potential legal ramifications of not disclosing a known material defect with the property.
Damp, even relatively minor damp, can cause mould to grow and with that comes a myriad of potentially serious health problems so any damp needs to be spotted and nipped in the bud before it becomes an issue.
