Hygroscopic salts line- due to rising dampness
Rising dampness 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 ruins internal decorations. This is why the plaster needs to be removed and replaced.
How do we cure the rising dampness?
First and most important is the survey, which is undertaken by one of our qualified surveyors. This is to ensure that the defects are due to rising dampness and not something else because installing a damp proof course will not cure other moisture defects like the lateral movement of moisture due to the high external ground or neighbour’s floor levels.
The surveyor will write a detailed report and specification for the remedial works required to the 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
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.
Initially, a cement render was applied to the wall surface, incorporating a waterproofer and salt inhibitors to prevent the lateral movement of moisture and hygroscopic salts to the decorative finish. Nowadays, many different damp-proofing plaster systems are available with BBA Accreditation, symbolising the 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, allowing the property to dry naturally without the risk of salts affecting the surface, which can occur with limelight base plaster. Conservation officers also endorse Modern renovating plaster systems for use in listed and period properties due to the high vapour permeability and low adhesive bond, which is around 0.1N/mm² and won’t damage the underlying structure.
Safeguard Drybase Flex system is a moisture/salt resistant low profile flexible membrane system fixed to the wall structure with a dry base adhesive. Allowing thermal insulation boards to be installed to improve the thermal value of the walls reduces heat loss and the risk of condensation/mould while lowering your carbon footprint, thus saving the environment as well.
Safeguards BBA Agrément applied to an external wall to allow thermal linings to be installed and save energy.
Chemical type damp proofing:
Chemical damp proof courses are installed in walls by various methods depending on the system employed. Still, the ultimate objective is to provide a water-repellent or pore-blocking material in a continuous horizontal band in the masonry, thereby providing 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 anywhere near as effective.
Plaster bridging installed damp-proof course level.
Floor-to-wall joint:
In older properties where the walls are affected by rising dampness about up to a solid floor, a floor-to-wall joint must be installed to prevent moisture from evaporating 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 underfloor/ DPC
In the image to the right is an area of wall stripped of plaster which abuts a solid floor, with the floor-to-wall joint installed linking the floor and wall areas. The system has been extended above the plastering line to prevent any possible bridging of the installed damp-proof course by plaster. BS 6576: section 6.1.5.
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Property remedial treatments and surveys in Oldham, Manchester, Rochdale, Stockport, Cheshire, and the North West. For advice or to arrange a survey, give us a call today!
Damp proofing and rising damp services in Oldham, Manchester, Rochdale, Stockport and Cheshire.
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If you have any questions, please call our Oldham office on 0161 633 9860 or our Wilmslow office on 01625 900 800, or fill in the contact form, and we will be happy to answer any of your questions or plan an inspection. (Inspection appointment refunds are subject to a Minimum 24hr cancellation notice.)