DAMP PROOF COURSE (DPC) FOR RISING DAMPNESS IN STRUCTURES AT GROUND LEVEL
WHAT IS RISING DAMPNESS?
Rising damp in buildings may be defined as the vertical flow of water up through a permeable wall structure, the water being derived from ground water. The water rises through the pores (capillaries) in the masonry by a process termed ‘capillarity’. In other words the masonry acts like a wick. The height to which the water will rise depends on several factors including pore structure and rate of evaporation. Masonry containing a high proportion of fine pores will allow the water to rise higher than a coarse pored material; basically the water is carried up the wall in the finer pores and not those of large diameter. The average size of pores in masonry gives a theoretical rise of around 1.5 meters but where evaporation is severely retarded, for example by the use of impervious membranes, tiled surfaces or surfaces behind wardrobes and cupboards/cabinets, moisture can sometimes rise in excess of 2 metres.
Residual salt deposit after walls dry up
Water rising through mortar beds of brick walls
Flaking paint, peeling wallpaper, a “musty” odour, and timber decay are among the most common symptoms of rising damp. Failure to treat the problem properly can result in a house that is unpleasant to live in and difficult to sell, so it is important to choose an effective method of treatment.
Damaged Walls due to Rising Damp
We use a a special damp-proofing cream that is introduced along the mortar course at regular intervals by injecting it into pre-drilled holes. The cream then diffuses before curing to form a continuous water-repellent barrier. This prevents the damp from rising up the wall. If the existing mortar joint to be injected is found defective, it we will have to be repaired with fresh mortar in order to aid complete diffusion of the damp-proofing cream.
RISING DAMPNESS DUE TO INTERNAL LEAKAGES ON UPPER FLOORS
Alternate treatment for internal leakages through tiled flooring…
All tile/marble pointing (joints) are re-cut up to 2 mm wide and 10-14 mm deep with specialty power tools, joints sucked clean of debris and then gravity grouted for 16 hours with an aliphatic polymeric ester added with filler material. The bathroom flooring will be kept immersed /flooded overnight at levels of about 20 mm with the above stated mix.
This procedure enables the solution to seep into the leakage causing pores and channels of the substrate between the existing tiles and the concrete floor slab and polymerise, thereby creating an impermeable barrier below the tiles. Additionally, it will also prevent rising dampness on internal walls. No bathroom tiles need to be broken or dismantled for the procedure.
Residual chemicals are mopped-up on the following day and tile joints are re-grouted with a flexible, colour-matching tile grout mixed with latex admixtures. The bathroom is to be kept dry /unused for a period of 24 hours thereafter for effective air curing. Total time required for completion is around 48 hrs per bathroom.
In order to complete an effective damp-proofing system it is extremely important that the new plasterwork which replaces the salt contaminated material resists the passage of residual moisture and contaminant salts from passing from the underlying substrate through to the new decorative surface. This procedure is important because the underlying wall can take many months to dry down following damp-proofing, but more importantly, the base of the wall may always remain damp due to the inherent limitations of the actual injection damp-proof course.
Finally it is important to understand that chemical damp proofing is a two step system to take complete effect.
Step 1 – The injection of the DPC and, Step 2 – The Replastering.