Identifying damp in my home

Unfortunately, damp is a really common problem in UK homes. Despite this, many people don’t understand what causes it and how to help mitigate the problem. In this blog, I am going to take a look at the different types of damp and ways of identifying damp, and how we can try to prevent it.

Why is damp in the home a problem?

Let’s first look at why damp is a problem. There are several key reasons: Damp causes mould, which is bad for your health and looks unsightly. Damp can cause structural damage to a property, especially if there is timber within the structure. Further, it can damage your walls and require constant cleaning and painting to keep it at bay.

There are 3 different types of damp that are commonly found in the home.

Penetrating damp in my home

This is caused when water gets through the outer barrier of the property, it can simply be the result of consistent rain, but roof defects, faulty brickwork, defective cavity wall insulation, or defective windows also can cause it.

This can obviously manifest in a number of different ways, and the solution will depend on the root cause, but as a starting point, brick work can be repointed, walls can be sealed and sealant can be applied to windows and doors to prevent water entering. In addition, you may want to consider rendering the entire property – since this will produce a water impermeable protective layer.

If you do decide to render the entire property, we also suggest insulating it (with external solid wall insulation) – this will help lower the heat demand of the property at the same time thereby reducing energy bills in the home, but it has an added benefit which is discussed further down.

Rising damp in my home

Rising damp happens when ground or standing water is drawn up through the brickwork into the home through something called capillary action. You will notice a property with rising damp because it will have a ‘tide mark’ on the wall where the water has risen. It tends to occur in old properties (100 years or more) which were not built with a damp-proof course. This is a barrier built into the wall that prevents the water from rising above it. Rising damp can also occur where the course has failed.

rising damp

A case of rising damp

There are several ways to treat rising damp including: addition of a damp-proof course, DPC injection, and draining the land directly around the building. These unfortunately can all be quite expensive!

Condensation in my home

This is perhaps the most common cause of damp in a property. There are a number of causes, but they usually boil down to a mix of excess water vapour in the property (caused by cooking, showering, and even breathing), combined with lack of ventilation (caused by blocked vents, poorly installed insulation, unvented windows etc.)

The best way to identify this problem is to test the humidity of the air. You can get a specialist in to do this, but there are some telltale signs. If you get beads of water on your walls and steaming up of your windows, chances are the damp is being caused by excess humidity. This will case mould to form in poorly ventilated areas of the room.


Condensation in London homes is becoming incredibly common as homeowners block up holes that have previously provided ventilation. Take for example old wooden sash windows; if you have have ever been in a property with these you will know how leaky they are – well these gaps around the window actually do help ventilate the property, so when they are replaced with airtight uPVC double glazing you can see how this kind of problem occurs.

It is also amazing the number of people that cover up ventilation from the inside of the property – all this serves to do is lock the moist air within the home.

The issue is that if the excess moisture in the air has no where to go and it comes in contact with a cold surface, it will condense which can lead to mould. So how do you deal with it?

    • Increase ventilation in the home
    • Increase the surface temperature of the walls so the water vapour cannot condense
    • Use dehumidifiers to remove moisture from the air

Increasing ventilation is relatively simple and involves unblocking previously blocked air holes in the property. You can also add additional vents in the home to help encourage the passage of the moist air out of the home. While cooking and washing, you can open windows to help get rid of the moist air too. Obviously one of the issues with ventilation is that cold air can enter the home through these vents – one way of avoiding this is to use heat recovery ventilation systems, which use heat exchangers to ensure that the heat in the air is not lost to the external environment.

There are a few options to increase the surface temperature of the walls, but remember this is not going to reduce the amount of water vapour in the air, it is simply going to inhibit it condensing on the walls. The first is to insulate the exterior of the property; this means that the brick work will warm up, since the warmth can’t travel through the insulation. The second is to use a heating system that uses radiant heating, since this too will raise the temperature of the surface it is directed at – infrared heating panels are just one way of doing this.

The final method is the least energy efficient since you are using technology to remove the moisture out of the air – these units are designed to suck in air, remove moisture and kick out the dryer air back into the room. They are not a long term solution though since they are expensive to run, so increasing the ventilation is always the preferred option.

So in summary to avoid condensation you can either reduce the cause of the humidity, or increase the ventilation. It may be possible to reduce the effect by opening windows when showering or cooking, not drying clothes indoors and using devices such as dehumidifiers, but you may need to go further and add vents to the property to help improve ventilation. Before all that though, make sure your current vents are not blocked – over the years they can easily get gunked up and stop them from airing the property.

So those are some of the major causes of damp – Hopefully this demystifies some of those common causes and helps you understand why your home is growing mould and gives you a few options to get it sorted!

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