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What Causes Rising Damp?

Line of bitumen damp proof membrane and a ventilation air brickRising damp is a common damp issue within older properties which is rarely seen in newer builds. Usually, when a property displays symptoms, it is because the Damp Proof Course (DPC) has been impaired, but that may not always necessarily be the case depending on the location and environment of the building.

Before we delve any further into the different rising damp causes, we must acknowledge that some falsely believe rising damp to be nothing more than a myth. Here at Garratt’s Damp & Timber, we can assure you that the risk of rising damp and everything that comes with it is very real, which is why we have a dedicated team of professionals on hand to properly investigate, diagnose and treat the issue.

Moisture in walls will travel up to around 1.2m high before gravity will stop the water from rising any higher. However, that does not mean that is where the effects of rising damp begin and end, with salt deposits appearing higher up the building as a result of non-breathing coverings on walls such as vinyl wallpaper and plasterboard, paint and render. Diagnosing the issue correctly is vital, otherwise, any repair work carried out will be a complete waste of time, leaving your property no better off than before.

Damaged DPC

The main reason why properties suffer from rising damp is because of a damaged DPC. Depending on the age of the property, this could be because the material used is not to the same standard as modern-day DPCs. Slate, for example, was a popular material as it is a water-resistant material. However, slate can be prone to cracking due to ground movement and settling of the building over many years, thus, its life expectancy is not as long as modern-day synthetic materials that are designed to last longer and move with slight changes in ground levels.

If the building dates back to the late Victorian era, a damaged DPC is likely to be the cause of a prevalent rising damp problem. Once the DPC is damaged, this allows for moisture to penetrate through and rise up through the walls of the property. Depending on the severity of the damage to the DPC and walls, repair work can range from a simple injection into the DPC to more invasive, and expensive, refurbishment.

Incorrectly Installed DPC

Just as a damaged DPC can result in the prevalence of rising damp so, too, will an incorrectly installed one. Often, a chemical injection will not be performed correctly, leaving the course penetrable and, thus, totally useless.

It is for this reason why calling on the services of a professional damp-proofing team is essential as you could end up paying twice. Once for the initial maintenance work, and again to fix the poorly carried out work.

No DPC (Common in Older Buildings)

Up until 1875 in London when legislation was brought in, buildings didn't need to have any form of DPC installed. This means that there is a chance that some older buildings standing today have not been fitted with a DPC course, although many have been as part of historical restoration and refurbishment works.

Without any form of DPC present, water is free to travel up through the pores in the wall freely, which can put the structure and, with that, the safety of all those inside at risk especially where timbers weaken. Increased levels of moisture risk rotting away any timber structural beams in contact with the foundation of the property, potentially causing severe damage.

In some cases, the increased moisture levels can result in an infestation of wet rot and/or dry rot, particularly in the sub-floor and basement area if the property has one. The presence of this will likely come with a musky, damp smell originating from humid areas of the building, especially those with little to no ventilation. To safeguard against this, it is recommended that properties are inspected by a professional damp-proofing team, such as Garratt’s Damp & Timber. Experts who will diagnose the problem and recommend any repair work, as well as discussing the potential for basement tanking to reduce the risks of damp causing damage to the property.

Bridged DPC

In the case of a bridged DPC, the effects are much the same as having no DPC at all. This is because, even though the DPC itself may be perfectly fine, the moisture has a bypass and can enter the property over the DPC. This happens when the external ground level, such as any adjoining garden, patio or driveway, has raised above the DPC. This can happen over many years and is again an issue mostly found in older buildings.

When the DPC is below ground level, there is nothing to stop moisture in the ground rising up through the walls of the property. If the DPC is in good condition and does not require any maintenance, the rising damp issue can be rectified without any actual work inside of the property. Lowering external ground levels adjoining the property should fix the issue as the DPC will no longer be bridged and, thus, moisture must penetrate the barrier to rise through the brickwork, however, ground salts may have already contaminated the internal plaster. The salts that rising damp presents are hygroscopic, they will remain in the plaster and continue to absorb internal water vapour.

Rising Damp Confused for Condensation

Often, rising damp is confused for damp which has been caused by condensation. This misdiagnosis can result in terrible damage the longer the true cause of the damp is left untreated. The main difference between the two types of damp is that whereas condensation will see black mould spores form on the affected surface, a sign of rising damp is a tide mark at the edge of where the moisture rises.

This is where the idea of rising damp being a myth originates from, because of cases where supposed experts surveying a property cannot correctly identify the difference between the two. It is dangerous to disregard the risk of rising damp as doing so puts the structure of the building, and all of those that are inside of it, at unnecessary risk of danger.


While the location of the property itself will not be the cause of rising damp, increased levels of moisture certainly can be. If the geographical location of the property commonly sees higher than average level of rainfall, this can be a contributing factor as there will be more moisture in the ground. The same can also be said for properties located close to the coastline or near a river, as these areas will be most susceptible to floods.

How Garratt’s Damp & Timber Can Help

If you suspect a rising damp problem in your property and want to know what the cause of it is, make sure to give the Garratt’s Damp & Timber team a call today. We will arrange for a survey where we will offer a diagnosis and a no-obligation quotation on the work that would be required to fix your damp problem.

For more information, please get in touch with us today on 0208 535 7536 or send us a message via our contact page. A member of our team will respond to your query as soon as possible.

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