Rising dampness is often the cause of structural damage in buildings. The internally rising groundwater saturates walls and pollutants, such as saltpetre, and this can lead to damage for your building materials. In time, constant dampness in walls can lead to mould, blistering, the peeling of paint and wallpaper, and damaged render, so call Smith Damp Proofing Ltd in Barnet, London today!
A common reason for rising damp, especially in older buildings, is an incorrect or damaged DPC or the lack thereof. As early as the beginning of the 20th century buildings in the UK were being damp proofed against rising damp and relevant building regulations were developed. However, these were not always adhered to and some of these DPCs will have become damaged over time.
Rising damp in walls, also called capillary ascending moisture, is the ascent of moisture through capillaries in masonry.
Capillaries are fine, elongated tubes with very small internal diameters. In masonry, these tubes are of varying thickness and can, in some cases, form cavities. The smaller the diameter of the capillary, the more the surface tension comes into force. This capillary force, which develops due to the surface tension, creates the effect of capillary action and causes moisture to rise. The smaller the capillaries, the higher moisture rises.
Capillary action means the rising of moisture in capillaries contrary to gravity. The effect of capillary action is used in medicine as well as in nature. To take a small blood sample, a very fine tube is held against a small cut, at the ear or a finger for example, and the capillary action draws the blood into the small tube. Plants use capillaries as water-conducting system for watering. In masonry, which contains fine piliform tubes, capillary action can have negative effects and lead to rising damp.
Rising damp is a much-disputed field, due to the common misdiagnosis of damp walls. The source of dampness should always be thoroughly investigated because an incorrect diagnosis can lead to further damage and unnecessary costs.
To prevent rising damp from affecting walls, houses have been built with physical DPCs for many years. However, these physical barriers do not always prevent rising damp from occurring. Especially in older houses, physical DPCs can become damaged over time or, in some cases, were installed improperly.
Additionally, when houses are being modernised or extended, building works can affect built-in physical DPCs. With a change of the ground level, for example, the physical DPC layer can be bridged and rising damp can appear where there had been done before. In such cases, a remedial DPC needs to be installed to prevent rising damp from recurring.
Rising damp often has negative effects on plaster, wallpaper, paints and skirting boards. To repair the effects of rising damp the source of the problem must be treated and the decor on internal walls has to be repaired.
Before a treatment to stop rising damp on internal walls can begin, all skirting boards around the affected area need to be removed. Additionally, all salt-contaminated plaster needs to be hacked-off to a minimum of 300mm above the last detectable signs of dampness or salt contamination, in most cases 1.2 meters from floor level.
Once the brickwork has been exposed, the treatment of rising damp can begin. By using Dryrod Damp-Proofing Rods, a remedial DPC can be injected directly into the masonry, ensuring a targeted treatment of the problem. Regardless of whether Dyzone or Dryrods are used, holes must be drilled into the lowest accessible mortar course that is still at least 150mm above the exterior ground level. These are typically drilled at a regular interval of 120mm, with a diameter of 12mm. When the holes have been prepared, the rising damp treatment can be injected. Inserting damp-proofing rods ensures a targeted, highly effective treatment of rising damp. Once inserted, a liquid membrane is then applied to the wall under the new DPC level.
Dryrod Damp-Proofing Rods have been inserted into a mortar course they are able to spread and form an effective damp‐proof course – blocking any further rising damp.
However, rising damp treatments are unable to undo any salt and moisture damage caused to plaster prior to treatment. Neither will they remove hygroscopic (moisture attracting) salts from the plaster that have accumulated over the years through the wall which was suffering from rising damp. For this reason, sections of plaster will often have to be replaced as part of an effective rising damp treatment strategy.
A two-coat rendering system with a sika 1 waterproofing additive will be applied to the brick work. Sika 1 is an aqueous solution containing complex colloidal silicates. In the presence of water these swell and block the capillaries and pores in the applied sand/cement renders, screeds and mortar to provide an effective barrier against the transmission of liquid water.
Once the render has dried a final coat of multi-finish plaster is applied, skimming over the render creating a smooth finish ready for painting. Once skimmed, skirting boards can then be refitted if not damaged.