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Rising damp in buildings

As with the treatment of any damp, the success of any repair will be dependent on firstly good diagnostics & investigation. Where rising damp is present in walls that have a damp proof course which is compromised by higher ground levels, bridging plaster render, or debris in the cavity; then removing the ‘bridge’ should hopefully be sufficient to control the capillary rise of moisture in the wall. 

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Rising damp treatment - salts on wall - Property Care Association

Two main considerations when treating rising damp

There are however, two main considerations for the treatment of rising damp: 

  1. Firstly, consideration should be given to the capillary rise of water and 
  2. Secondary, to the accumulation of hygroscopic salts that are typically contained within groundwater and deposited within the wall as evaporation occurs. 

Even when the source of capillary rise has been addressed there may still be a need to address the accumulation of salts. When also considering the many methods for controlling rising damp, the remediation approach you chose to adopt might also be determined by a number of factors including; 

  • Age 
  • Construction type 
  • Heritage/ architectural significance 

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Typical types of rising damp treatment

As previously explained there are two considerations when considering rising damp, the control of capillary rise of water and the removal of any salts that may have accumulated. Below are some of the methods that can be adopted for the retrospective treatment of rising damp in buildings. 

+ Physical Damp Proof Courses:

In some instances, it may be possible to install a new physical damp proof course. This type of system is limited to certain construction types and is not suitable for flint, rubble filled or unusually thick walls. The presence of services can also prove problematic for the installation of a physical damp proof course. Where the insertion of a physical damp proof course is not viable, the Building Research Establishment (BRE) strongly recommend that alternative methods should only be considered if they have been awarded a third-party accreditation. The only method currently satisfying this requirement is an injected damp proof course.

+ Chemical Damp Proofing Courses

In most instances the installation of a chemical damp proof course is economically the most viable option for the control of rising dampness. Chemical damp proof courses currently fall into four groups;  

    •       Hand insertion – typically thixotropic materials and the most commonly used today 
    •       Low pressure injection
    •       Gravity feed
    •       High pressure injection

If there is any doubt about the suitability of a particular system, the manufacturer should be contacted for advice.

+ Electro Osmosis Systems:

The lack of a British third party accreditation for electro osmosis systems restricts its acceptance but can be favourable to some who like that this method of treatment can easily be removed from the structure if desired in the future. 

+ Dry Lining Systems: 

The systems detailed so far all look at preventing the capillary rise of moisture in a wall and additional consideration will need to be given for an appropriate plaster system. However alternative options are detailed below.  Not recommended as the primary or a long-term remedy for the control and eradication of rising dampness in masonry walls but has been adopted by industry as a means of isolating finishes from damp structures during the drying process and isolating finishes from salt affected masonry walls. The technique can be adopted in some circumstances to speed the recovery of damp structures and combat salt staining problems. T

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PCA’s step by step approach to treating rising damp

Whether you are a building or construction professional; below is a series of recommended steps you should consider or expect from a professional investigating and proposing remedial treatments for rising damp: 

  1. All areas affected by rising damp (from what you have been asked to inspect) should be identified and logged against appropriate reports. If you are unsure what to do or what to inspect during the initial inspection,  consider additional learning via our investigating dampness page
  2. Features that may be causing the rising damp issue should be clearly indicated and solutions proposed
  3. Any wet rot or dry rot issues as a consequence of the rising damp issue should be identified and marked out
  4. After due consideration and investigation, taking into account the type of property and any heritage issues, the most appropriate rising damp treatment should be identified. In most instances, the viable option will typically be in the form of a chemical damp proof treatment.
  5. The affected plaster should be removed and replaced using specialist plaster
  6. If necessary, any timbers affected by rot should be replaced.
Free training - Dampness related CPD videos

Want to learn more about treating rising damp

For those interested in learning more about the treatment of rising damp, as well as other forms of dampness, there is a variety of PCA training options for surveying professionals as well as technical/trade professionals. 

Use the search tool below to find available dampness related training courses or simply go to our training & qualifications section.  Alternatively, if you want to chat to someone, contract our training team on 01480 400 000 or contact them online.

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Surveying dampness in historic buildings

For more helpful information, help and advice specifically for professionals on surveying dampness in historical buildings, click the link below.

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Damp proof courses & membranes

Looking for training courses on damp proofing and membranes? Click the link below to learn more.

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