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In this article we will be looking at damp proofing internal walls, and some of the common causes for damp on the internal walls of a property.
Damp internal walls are a common problem for many homeowners. The problems are various too. Damp internal walls can create a general feeling of dampness in the home with a musty, unpleasant smell attached. Over time, if left untreated, it can be damaging to our health as it can cause (or worsen) respiratory conditions. Homes feel colder as damp affects heat insulation. On top of this, it’s unsightly and can lead to structural damage. So, damp proofing internal walls is something that needs to be done. But, the good news is that there are plenty of solutions out there.
Before you can decide on the best course of action, you need to determine which type of damp is affecting the property.
Condensation is perhaps the most common form of damp in the home. It’s also the easiest to address – and the cheapest.
Condensation occurs from everyday activities such as cooking, washing and drying clothes indoors. Essentially, condensation is excess water vapour that deposits itself on cold surfaces, such as walls and windows. Symptoms of condensation include steamed-up windows, walls feeling damp to touch, peeling wallpaper and black mould spots on ceilings.
In the vast majority of cases, condensation can be dealt with relatively easily. Ensuring the property is better ventilated – simply by opening windows to allow air to circulate, and by installing extractor fans in the kitchen and bathroom, for example. It’s best to have heating on constantly on a low setting and avoiding sudden changes of temperature and even keeping lids on pans when cooking and not drying wet clothes on radiators – anything that reduces moisture in the home – can make a difference.
Other solutions include damp proof paint and anti-mould paint. These are inexpensive and effective even in properties where condensation is a consistent problem. Not only can damp patches and mould be easily painted over, it should ensure that it won’t come back.
However, damp proof paints should only be used once the cause of the damp has been identified and rectified. If the only issue is condensation damp, then it will work fine, but it will offer only temporary respite against other types of damp, such as penetrating damp and rising damp, if these lie untreated.
Damp proof paint is often used under a render to provide an extra layer of waterproofing when damp proofing internal walls.
Penetrating damp is when water penetrates from outside. Usually, this is a result of some sort of building defect such as roofing and masonry faults or damaged or blocked guttering and pipes. Whether it’s a roof that needs fixing, cracks or leaks in guttering or gaps around windows and doors that need addressing, the underlying cause of the penetrating damp must be rectified first.
Penetrating damp can also be caused by problems with the cavity walls. All modern homes have a cavity between the exterior and interior walls. This space allows moisture from the external wall to evaporate before it reaches the internal wall. Where doors and windows sit along a wall, a cavity tray is needed. If there isn’t one in place, you may need to add one and it might be that the existing one is defective and needs repairing.
Cavity work is relatively inexpensive. Clearing blocked cavities to prevent damp from external walls reaching inner walls typically costs approximately £130 per affected area. If a new cavity tray is needed, prices are likely to be around £250.
This is an important thing to remember about damp proofing internal walls. With the exception of condensation damp, damp comes from outside, so dealing with external issues is crucial to sorting out the effects of damp internally.
Again, once the remedial action is taken to address the causes of the penetrating damp, a damp proof paint such as Johnstones might be appropriate to add a further layer of protection for the future.
Rising damp is less common but often trickier to remedy and can be expensive. Usually it is caused because of a defective (or missing) damp proof course. In most cases, this means that a new damp proof course will be necessary. A new damp proof course can cost upwards of £400 for one wall. An injected silicone damp proofing treatment will be more like £700. However, relatively inexpensive DIY kits are widely available too.
Tanking is a form of internal damp proofing that blocks water ingress by creating a barrier by sealing the walls with a damp proof material. It’s not a cheap solution, however. To remove damage to a wall and its covering and then to tank and redecorate could set you back over £3000 for a 3×3 metre room.
A cheaper option is to use a damp proof membrane. DIY kits to cover 20m² can be picked up for as little as £150. Often used after the installation of a new DPC, a damp proof membrane can be placed on the internal wall to provide an impermeable barrier.
In older properties renovating with damp proof plaster is an option. It helps to reduce condensation and is particularly effective in basement areas. It can be used after the installation of a new damp proof course and it contains waterproofing qualities that helps to contain the growth of mould.
Whichever method of damp proofing internal walls you choose, it is important to remember that the underlying cause of the damp has to be addressed first. The suitability of particular options will be determined by the extent of the damp and the damage it has caused to the property.