Rising Dampness

Hygroscopic salts line- due to rising dampness

Hygroscopic salts line- due to rising dampness

Rising damp results in unsightly damage to internal decorations, which will lead to timber decay and heat loss through the wall. In addition rising moisture from the ground, carries with it hygroscopic ground salts such as chlorides and nitrates. Which have the natural ability to absorb moisture from the atmosphere leading to the wall becoming damp in conditions of high relative humidity. The cyclical nature of the crystallisation and rewetting of these salts breaks down internal plaster and ruin internal decorations, this is the reason why the plaster needs to be removed and replaced.

 
 

How do we cure the rising dampness?

First and most important is the survey, this is undertaken by one of our qualified surveyors. This is to ensure that the defects are due to rising dampness and not some other defect, installing a damp proof course will not cure moisture defects, due to lateral movement of moisture due to a high external ground or neighbours floor levels.

The surveyor will write a detailed report and specification for the remedial works required, to BS6576:2005+A1:2012 ‘Code of Practice for the Installation of Chemical Damp-proof Courses’ ensuring that your problem is cured and also guaranteed, with a fully insured GPI independent insurance.

General treatment methods

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Originally a cement render was applied to the wall surface which incorporated a waterproofer and salt inhibitors, to prevent the lateral movement of moisture and hygroscopic salts leeching through to the decorative finish. Nowadays there are a number of different damp proofing plaster systems available, with BBA Accreditation which is the symbol of quality, reassurance and integrity of building products within the construction industry.

Renovating plasters are lighter based plastering systems, produced by Safeguard, Wykamol and Koster which prevent the lateral movement of hygroscopic salts, they are vapour permeable so allow the property to dry down naturally, without the risk of salts affecting the surface, which can occur with limelight base plaster. Modern renovating plaster systems are also endorsed by conservation officers, for use in listed and period properties, due to the high vapour permeability and low adhesive bond which is around 0.1N/mm2, not resulting in damage to the underlying structure.

Safeguard Drybase Flex system is a moisture/ salt resistant low profile flexible membrane system fixed to the wall structure with a drybase adhesive. Allowing thermal insulation boards to be installed to improve the thermal value of the walls, so reducing heat loss, risk of condensation/mould and lowering your carbon footprint, so saving the environment as well.

Thermal Lining
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Safeguards BBA Agrément applied to an external wall, to allow thermal linings to be installed ‘Saving energy.’

PLASTER – IN CONJUNCTION WITH DPC INSTALLATION

Chemical type damp proofing Chemical damp-proof courses are installed in walls by various methods depending on the particular system being employed, but the ultimate objective is to provide a water repellent or pore blocking material in a continuous horizontal band in the masonry, thereby to provide a ‘barrier’ to water rising from the ground.

It is a fact that the only continuous pathways through which water can rise through a masonry wall are the mortar beds, it is therefore essential that the damp-proofing material installed impregnates the mortar courses since this forms the pathway for the rise of water within walls. Damp-proofing into the bricks will not be anything like as effective.

Plaster bridging installed damp proof course level

Plaster bridging installed damp proof course level

Floor to wall joint
In older properties where the walls affected by rising dampness abut up to a solid floor then a floor to wall joint must be installed, to prevent moisture evaporating out from under the floor slab.
This image shows a typical scenario where the damp proof course failed due to the floor to wall joint being omitted, resulting in the plaster bridging the DPC and the skirting board being affected by fungal decay, due to moisture evaporating from below the installed damp proof course and solid floor void.

Floor to wall joint, to prevent the escape of moisture vapour from under floor/ DPC

Floor to wall joint, to prevent the escape of moisture vapour from under floor/ DPC

In the image to right is area an area of wall striped of plaster which abuts a solid floor, with the floor to wall joint installed, so linking the floor and wall areas. The system has been extended above the plastering line, so to prevent any possible bridging of the installed damp proof course by plaster. BS 6576 : section 6.1.5.

 
 

Olympic Construction are Property Care Association Members

Property remedial treatments and surveys in Oldham, Manchester, Rochdale, Stockport, Cheshire and throughout the North West. For advice or to arrange a survey, give us a call today!

Damp Proofing, Rising Damp services in Oldham, Manchester, Rochdale, Stockport & Cheshire.

Would you like to talk?

If you have any questions please call us on Oldham 0161 633 9860,
Wilmslow 01625 900 800
or contact us and we will be happy to answer any of your questions or make arrangements to undertaken an inspection.
(Inspection appointments refunds are subject to a Minimum 24hr notice)