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Rising Damp

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Rising Damp: What is it & How to Treat it?

Rising damp is the general term for water that is absorbed by the fabric of a building from the surrounding ground, often resulting in damage to the ground floor walls.

Rising damp is a complicated and controversial property problem because it can easily be misdiagnosed by unqualified tradespeople and this can result in ineffective treatment being applied. Our specialists have prepared this helpful guide for you to understand if those damp stains on your walls are actually rising damp, and if so, what is the best form of treatment to solve the problem for good. If you think your property is suffering from rising damp you can call the qualified and experienced team at Rentokil Property Care today on 0800 0121 437 or click the button below to book a survey online.
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What is Rising Damp?

The term “rising damp” describes the process whereby ground water is drawn upwards through the mortar and masonry of a building by means of capillary action. Porous building materials such as bricks and sandstone are the most likely to be affected.

All building materials have complex pore structures and the smaller the pores, the higher the water can rise. This moisture often brings groundwater salts and other contaminants with it, and these deteriorate building materials and decorative fixtures and fittings.

In most cases rising damp is a slow process and may be present in a building for several years before any signs of a problem appear. The speed at which the moisture rises up the walls will depend on several factors including:

  • The type of wall or floor construction
  • The nature of the ground
  • The environment inside and outside of the building

What Causes Rising Damp?

Ultimately there are only a few property problems that can result in rising damp. If your home has a damaged damp proof course, no damp proof course or the damp proof course has been bridged by the raising of external soil or the build up of debri in a cavity wall, then rising damp is a possibility. If none of these sounds likely, but you still have damp problems then it is more likely that your property is suffering from penetrating damp or condensation.

Failed Damp Proof Course

Many properties have a slate or bitumen membrane barrier installed approximately 150mm (6in) above ground level in the ground floor section of the wall to prevent rising damp. This is called a Damp Proof Course or DPC for short.

Unfortunately, these DPC’s can fail due to age, deterioration, or damage caused by factors like subsidence. Modifications to a building like an extension or conservatory that have been built without a damp proof course also increase the risk of rising damp.

A Bridged Damp proof course

A new installation like a flowerbed or new driveway can raise the ground level and bridge the DPC. Essentially this means that your rising damp barrier has been skipped over and the groundwater now has direct access through to the porous building materials straight into your home again.

Damp proof courses can also be bridged if debri in a cavity wall piles up above the height of the course.

How to Identify the Signs of Rising Damp

It can be difficult to identify rising damp because some of its symptoms are easily confused with those of other damp problems such as condensation or penetrating damp.

That said, you can look out for the following signs that are typical of a rising damp problem:

  • Damp tide marks along the lower wall
  • White salt deposits on the lower wall
  • Damp patches coming from brickwork / masonry
  • Stained and damaged wallpaper and paint
  • Damp and musty smell
  • Damaged plaster
  • Decaying timber e.g. skirting boards, floor boards, floor joists

The signs of rising damp listed above would typically be evident to a height of about 1 metre (3.3 feet) from the ground.

rising damp example wall staining on internal wall

Treating Rising Damp

Treating rising damp can be a tricky task to take on independently due to the various potential causes and the accuracy with which the treatment must be applied to be effective. This is why we provide specialist rising damp solutions that are covered by a 30-year guarantee which can be passed on to future owners of the property for complete peace of mind.

The steps below cover what you can expect from rising damp treatment by Rentokil Property Care:

  • Rising damp survey - Using their extensive experience and expertise, a Rentokil surveyor will carry out a detailed survey to pin-point the most appropriate rising damp treatment for your property. This plan will include some combination of the treatment options below...

  • Install a remedial damp proof course - Dependant on the thickness of the walls, holes are drilled in the mortar/brick to a pre-determined depth and at the correct level and spacing. These holes are then injected with a low odour water based silicone damp proofing fluid (damp proof course) to reduce the movement of water through the capillaries.

  • Repair or replace a damp-proof membrane - Damp proof membranes can also be used in rising damp treatment. These membranes can be installed immediately after the injection or repair of a damp proof course and used as a key for any new plaster. The membrane will separate any new plaster from existing salts and other contaminants on walls.

  • Re-plastering - Once our team has completed treating your home for rising damp our technician will ensure any treated walls are re-plastered with a waterproof additive.

Treating Rising Damp on Internal Walls

Most property owners identify a rising damp problem when they spot damp patches on their internal walls. Before any treatment for rising damp on internal walls can start, technicians will need to lift skirting boards around the affected area and remove any plaster that has been contaminated by hygroscopic salts.

Once the area has been prepared out technicians can begin installing a remedial damp proof course via our DPC injection method.

How to Treat Rising Damp on External Walls

Rising damp problems caused by elevated ground levels can often be solved by simply removing excess soil back below the damp-proof course - this would be the case if a raised flower bed was the culprit for example. When a more permanent fixture or alteration has bridged the damp proof course, a damp proofing solution that adapts to your property will likely be required. A qualified surveyor will be able to make the best recommendation.

Is Rising Damp a Myth?

There is a school of thought out there that suggests rising damp is a myth, this is simply not true. Water rising through porous stone and brick via capillary action has been observed for centuries and is easily replicated by putting common building materials into water.

The reason there is controversy around rising damp is due to the high number of tradespeople who lack the experience and qualifications to correctly diagnose and treat this damp problem.

When other problems like condensation or penetrating damp are treated as though they are rising damp it is inevitable that the treatment fails and the property suffers.

So, it goes without saying that where rising damp is the genuine cause of the damp problems in your property it requires a survey and treatment plan from qualified professionals.

Buying a House with Rising Damp

If you are interested in a property that has rising damp listed on the home report it is certainly something you should have surveyed. The qualified and experienced surveyors at Rentokil Property Care will be able to establish why the rising damp is occurring and the best form of treatment to stop it.

Contact the Rising Damp Specialists

Providing all of our customers with the highest quality of service is our highest priority. This is why we ensure all our surveyors are Certificated Surveyors in Remedial Treatment (CSRT) and our technicians are trained to Property Care Association (PCA) standards.

Our team of experts will assess and correctly diagnose the extent of your rising damp issue. From this, we provide recommendations on specific damp proof treatments for the most effective ways to treat your problem. You can contact our expert team at Rentokil Property Care today on 0800 0121 437 or click the button below to book a survey online.

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