What is rising damp

Your cavity wall may also have debris inside of it, whether it is leftover building materials or something else. Rising damp can happen as a result of debris present in your cavity wall bridging the Damp Proof Course and giving water a way to travel around the DPC and up into your walls. Remember that your damp problem may not necessarily be caused by rising damp — there may be another source of water that you are not aware of.

A telltale sign that your damp is not rising damp is if the damp patches are higher up than 1 metre on your wall and are unevenly distributed, in which case you may be suffering from penetrating dampness instead. Uneven damp patches higher on your wall than 1. If, at any point during the diagnosis process you feel that you need some additional insight or advice please call Property Repair Systems on They will be able to offer you assistance free of charge.

You should first check that you have a Damp Proof Course — this will usually be visible outside your house as a line 6 inches above the ground. If you do have a DPC, check that there are no structures bridging your DPC — examples include higher outside ground or outside steps that are higher than your DPC and internal plaster that directly meets a solid floor.

If you do not have a damp proof course or it is bridged or below ground level this could be causing your rising damp problem. As mentioned earlier, your DPC may also be bridged internally.

This happens when your cavity wall becomes filled with debris, which can happen during the building of your house. This can reach higher than the level of the DPC, allowing water to travel up it and over the DPC, then it can travel, via the bridging material, through the wall to the inside. Using a phone with a light or a camera, take a look around the cavity.

If there is debris there, you can take this out by hand if you can reach it use sturdy gloves to avoid injuring yourself on sharp objects and use a bar to drag any out of reach objects closer to you. To get smaller bits and dust out, use an old vacuum cleaner. Once the cavity area you have access to is clear, replace your bricks. You need to identify the cause, deal with it and then carry out the necessary repairs to deal with the effects.

Carrying out a quick-fix for rising damp, e. A damp proof course is a waterproof barrier that spans the width and length of your wall. It stops water from the ground rising up through the wall through capillary action. The DPC needs to be installed at least six inches above ground level according to British Standard and Building Regulations also state it should be at this height. There are plenty of easier retrofit DPC options available — these include:.

Whichever method you choose to use, you will need to install your DPC on both your internal and external walls if you have a cavity wall. Hopefully, our guide will help with this. Most people first notice an issue with rising damp on internal walls. Rising damp often results in tide marks on your internal walls up to the height where the water has reached. In most cases, these tide mark stains appear up to a metre above the skirting board. In some very rare cases, water can travel beyond this point.

The height the water reaches depends on several key factors. These include the pore structure of the bricks and mortar and the rate of evaporation. Masonry containing a high proportion of fine pores will allow the water to rise higher than one with less pores. Rising damp can occur up to 1. The water from the ground often contains salts that are then deposited on the wall when the water evaporates.

These salts can cause the paint to bubble and a white fluffy deposit to be left on the surface. There are two main types of salt - sulphates which result in crusty white patches and invisible hygroscopic salts known as nitrates and chlorides. The hygroscopic salts continue to draw moisture and therefore must be treated. Salts debonding the paint work - if you look at the top of the bubble you will see the white fluffy salt deposit.

Rising damp in internal walls is caused by the same movement of ground water up through the brickwork by capillary action. Rising damp can affect both internal and external walls. When looking for evidence of rising damp on external walls, again you should keep an eye out for tide marks. You may also see some of the mortar crumbling between the bricks or stonework and salt deposits too.

Rising damp is a relatively rare form of damp and treatment will only work if it is correctly diagnosed. It is therefore vitally important to get a professional diagnosis from a qualified surveyor — this will involve a rising damp survey of your home including analysis of the salts. It can be hard to distinguish rising damp from other forms of damp like condensation or penetrating damp.

Having said that, the following are some of the more common signs of rising damp that you can look out for:. Rising damp is often characterised by the tide marks on your wall above the skirting as well as powdery white salt deposits. It can cause plaster to bubble and wallpaper to peel away. The following rising damp images give you an idea of the visual appearance of the signs of rising damp:. Rising damp can be a serious problem, as if left untreated it can lead to structural issues. The damage it can cause to your plaster, flooring and decorative finishes as well as the smell also makes it very unpleasant to live with.

As with most forms of damp, rising damp is not good for your health, making some respiratory conditions much worse. It can also result in increased heat loss, leading to higher energy bills. If you are in the process of buying a house and a survey carried out by a RICS-approved surveyor suggests that you may have an issue with rising damp, you should investigate further. We would recommend getting a professional damp company to carry out a rising damp survey before completing on the property.

You will want to get a qualified surveyor ideally with industry-recognised professional qualifications. If your property was built after the s, you would expect to find some form of DPC whether it be bitumen or slate. It is rare that this will have deteriorated unless there has been some subsidence which is a very serious issue in itself. Another potential reason the DPC has failed is that it has been bridged, usually by debris or insulation in the cavity wall that exists below the DPC level.

The ground levels outside could have also risen above the DPC level. The rate of flow of water through the structure is dependent on pore size, shape, and connectivity. Smaller pores have greater potential for capillary rise, but larger pores have more rapid flow. So the maximum rise is determined by the distribution of pore sizes. In practice, this potential height of rise is moderated by the fact that moisture introduced into the wall through rising damp will evaporate before it has had a chance to rise to the full potential height.

For this reason, rising damp to heights exceeding 1. The height of rise also tends to be higher in other situations in which evaporation is inhibited — e.

Figure 3: Less surface area results in a slower rate of evaporation. This is because rising damp transports hygroscopic moisture attracting salts from the ground into the building structure where they accumulate.

Hygroscopic damp — In this case it has not been caused by rising damp, but by hygroscopic salts in a chimney breast caused by the burning of coal. When hygroscopic damp has taken hold in a wall it becomes a cause of dampness in its own right and can therefore continue to be a problem even though the rising damp has been rectified e.

This is one of the reasons that it is sometimes necessary to carry out specialist replastering as part of a rising damp treatment. Options for replastering walls affected by rising damp are discussed later in this guide. Figure 4: Hygroscopic damp caused by soluble salts rising up the wall. When this occurs inside the pores of masonry materials the expansive forces can cause damage to the masonry material e. However plaster and masonry that has already been damaged by salts may need to be repaired or replaced.

In very damp conditions, the inorganic materials themselves may lose their structural strength. This occurs most spectacularly with walls made of cob earth soaked with water. Damp conditions on the surface of walls, particularly in conjunction with condensation, allow the growth of moulds both on the surface and within porous or fibrous materials, such as wallpapers or carpets fitted against the base of the wall. Not only is this aesthetically unacceptable and damaging to finishes, but it can be a significant health hazard to occupants.

Where evaporation takes place, the deposition of soluble salts on the surface or within the pores of materials can cause aesthetic and structural damage. As described above, 'rising damp' is only one of many mechanisms resulting in high moisture levels in the base of walls, and even when it is a significant factor, it is rarely the primary source of moisture.

The management of problems due to high moisture levels requires the proper identification of the moisture source and the defect responsible, before the most cost-effective solution to the problem can be determined. Damp and its effects may then be controlled by adopting one or more of the following measures:. The provision of suitable moisture sinks to dissipate the moisture at its source without causing problems to the structure or occupants, and the repair of any contributing defects acting as moisture sources, such as broken pipes.

The introduction of either physical barriers using damp-proof membranes or materials to form a 'damp-proof course' or hydrophobic water-repellent materials as in 'chemical damp proof courses'. The isolation of vulnerable materials such as timber and interior finishes from damp fabric.

The control of moisture movement using either damp-proof or hydrophobic materials to create a relatively less permeable 'moisture barrier' is not necessarily a cost-effective option in controlling damp problems and may even be counter-productive.

This is because use of relatively impermeable materials will restrict moisture movement and hence drying. As a result, moisture may be 'locked' into damp materials for many years causing chronic problems. Moisture may also be prevented from dissipating from permeable materials, resulting in the build-up of moisture or even damper conditions in localised areas. This may result in moisture moving into previously dry structures or evaporating from previously unaffected surfaces, causing further salt efflorescence.

One reason why those injecting 'chemical damp-proof courses' generally insist on re-plastering treated masonry with a salt-proof and waterproof mixture, is to cover up these potential problems. A relatively common example of the effect of inserting a damp-proof material into a structure is the appearance of fresh 'rising damp' in walls following the laying of a new concrete floor with a damp-proof membrane. This is most often done when a suspended floor structure is replaced by a solid floor, or when a breathable stone slab floor is lifted and re-laid.

Before the alteration of the original floor, moisture would have been able to evaporate off a large surface, without affecting internal finishes. However, a new impermeable membrane allows the water to accumulate beneath, forcing it to the sides of the room and into the base of the walls.

These damp problems are then often used as justification for the injection of a moisture-barrier and the removal and replacement of plaster with remedial mixes. In fact, the more cost effective solution would have been to allow the floor structure to continue to breathe.

If it is decided that a moisture-barrier at the base of the wall is essential, the most reliable method is to introduce a physical barrier rather than a chemical one. This involves cutting in a layer of damp-proof material to form a barrier which is continuous with the damp-proof membrane under the floor. As the wall above this barrier will remain damp for some time, it is then necessary to isolate all vulnerable materials above as well as below the barrier, such as skirting boards, from the base of the wall with a damp-proof membrane or ventilated air gap.

However, a damp-proof barrier is always vulnerable to local failure and will tend to concentrate moisture and damp problems at these points.

This is a general characteristic of all impermeable materials, including those used in tanking systems, which are generally found to fail at some point or at some time.