Recommendations of treatment.
Where rising damp has occurred the passage of water from the ground brings with it the dissolved salts. As the water evaporates these salts become concentrated in the plaster / masonry. Where there is severe contamination with salts visual welling occurs, leading to the continued spoiling of any decorative finish. Similarly, the movement and subsequent concentration of soluble sulphates will cause deterioration of the render, and could cause the final disintegration.
Having inserted a chemical DPC and eradicated all other sources of the moisture e.g. (penetrating damp), it is essential that all contaminated plaster be removed to a height of at least 1 metre, and beyond any ingress off moisture, and the exposed wall should be thoroughly wire brushed and joints raked out.
Replastering: Reinstate with a 3:1 sand and cement first coat with a liquid waterproofer. Apply a second 3:1 sand and cement coat gauged with clean water only, whilst the first coat is still green. Finish with a siraphite plaster coat. Liquid waterproofers to be used to specification of manufacturers.
It is importand that the right grade of sand is used. Sand should be salt and loam free, specified to fit the requirements of ZONE 2 grading as laid down in British Standard 882. Rates of drying walls, masonry, etc vary and may be a slow as 25mm per month, depending on conditions and the amount of dampness in the brickwork up to the time of treatment.
As an alternative to the above specification Limelite Renovating Plaster and Finish may be used. No other products are acceptable. Any external render should be kept above the level of the damp course.
It should be noted that where floors are solid the new plaster should be kept 75mm above the level of the floor.
Redecoration – No wall papering will take place until the plaster is completely dry and free from salts. This may take between 6-9 months and, in some cases, a maximum of 18 months. However, the client may emulsion the new plaster with a water based paint approximately 4 weeks after the re-plastering has been carried out.
Important: General Damp Proofing will not be responsible for making good or re-decorating. However re-plastering details are set out above and an estimate is available on request.