Rising or lateral damp is a condition found in masonry buildings that, if left untreated can cause progressive damage such as deterioration of bricks and morter, rotting of timber and the spread of rust in steel reinforcement known as concrete cancer. The initial signs of damp issues in buildings include softening plaster, bubbling render and peeling paint as well as muscy smells and visible mould.
Damp in houses is often the cause of family health conditions such as allergies, asthma, cold and flu and mould infestations.
Please visit the below link for the harmful health effects of damp in homes.
In older buildings rising damp generally occurs because the damp proof course breaks down. This is a barrier originally placed low down in the wall between the bricks in order to prevent moisture, which occurs naturally in the foundations, from rising up the wall due to hydroscopic action, i.e. the bricks suck up moisture like straws.
This barrier was originally made of slate, but after about 60 years or more it can break down and stop doing its job.
The moisture then begins to rise up the wall, bringing with it ground salts which, over a period of time, become more and more concentrated in the wall until the plaster or render surface inside the building begins to flake and the paint begins to blister.
This process is detrimental to the building's walls and may be arrested for a while by repainting and simply covering the problem but it nearly always returns.
In some cases it may cause the house to smell musty and damp and become a contributing factor in mould infestations. It may also develop into a health hazard causing breathing difficulties, allergies and flues in some people.
When cement rendering a wall, the damp proof course must not be 'bridged'. Bridging occurs when the renderer continues over the top of the damp proof course and onto the bricks below which are free to draw moisture up from the footings and foundations. To stop this problem from occuring, the DPC must protrude out from the course of bricks an equal distance to that of the thickness of the coat of render being applied, or alternativly, stop the render short of the DPC. The remaining gap to the floor can then be covered using skirting.
A common cause of damp problems in walls is the build up of water pressure in the foundations behind the wall. This often occurs in bedrooms below ground floor level such as basements, pool rooms, garages and guest rooms.
Depending of the amount of water build up behind the wall this problem can be difficult to fix. The three main methods to permanently repair the problem include:
a) Installing agg lines and drainage behind the wall, removing the problem at its source
b) If the other side of the wall can not be reached, use a membrane sealer that functions under negative pressure conditions
c) Creating drainage on the inside of the room, allowing penetrating water to run away
Again, many situations are unique and one or more of the above sugestions may be required.
Time after time we see this situation occuring. In homes that were originally constructed with timber floors heald up by bearers and joists allowing moisture and air flow under the house. The house is then renovated and concrete slabs are poured on the ground. This slab stops any water from evaporating or flowing away and creates a pressure build up which forces moisture vertically, up between the newly formed slab and existing wallls, or directly up inside the walls which may have old slate DPC that can't repel the increased level of moisture causing rising damp to breakout.
For More infomation on rising damp and methods of repair visit - http://www.lifestyle.com.au/property/the-causes-of-and-cures-for-rising-damp.aspx
In our years of business in Syndey we have over time begun to see patterns establish in regards to damp in buildings characteristic of particular Sydney area due to the topography of the land, foundation type and material, style of building in the area and the era in which most building were built in the area.
Many of Sydney's terrace and town houses were built in the early 1900's. They were built using mainly double brick walls with no cavity between the inner and outer skins, allowing moisture to pass through to the inner wall. They were also built using a slate damp course which, as mentioned earlier breaks down after about 70 years. They were originally designed to have bearer and joist floors but over the years slab on ground construction has become the preffered way in modern renovations. This can cause hydrostatic pressure and cause water to track up the brick work courses. Areas around Sydney which are most prone these propblems include: Edgecliff, Paddinton, Waverly, Bondi Junction, Surry Hills, Newtown, Balmain, Pott's Point, Rozelle, Birchgrove, Leichardt, Stanmore, Annandale, Camperdown, Enmore, Redfern, Darlington and Kensington.
Sydney has recently (March 2012) experieced the highest level of rainfall in over 100 years. As a result we have been called out to many houses that have experinced problems invovovled in the water table and ground water under their house to rise and penetrate through walls and slabs to cause damp issues. These include the usual signs of rising damp such as bubbling render, peeling paint and leeching salt, but also broblems such as basemnt floods, staining of marlble floor slabs, rotting timber frames etc.
The suburbs which are most prone to the type of problem include those which are lower lying and were once swamps or wet lands. These include: Double Bay, Bellevue Hill, Rose Bay, Cammeray, Lane Cove, Willoughby and much of the North Shore of Sydney.
Leaking balconies are most commonly cause by failure of the waterproofing membrane used to treat the slab before tiling. Time after time we see incorrect and lazy methods used which have in the end cost our clients time and money to have repaired. When we repair these types of defects we ensure the problem will never happen again by using a two coat water proofing system to seal the salb, laying the tile bedding using a high cement mix with minimal sand and ensuring all fall are done correctly. We then do a second, two stage waterproofing system that completely seals the slab before the tiles are finally laid. Our method also stops leeching balcony edges which are all to common in buildings around Sydney. Areas that we spend a lot of time in rectifying these problems include: Vaucluse, Dover Heights, Bondi, Darling Point, Point Piper, McMahons Point, Kirribilli, Castle Crag, Middle cove, Mosman and Cremorne.