What Is Rising Damp?

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.


There Are Two Main Causes Of Rising Damp

Rising Damp in Older Buildings

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This barrier was originally made of slate, but after about 60 years or more it can break down and stop doing its job.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.


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Main Causes of Rising Damp In Newer Buildings


In newer buildings, which have generally been built with more durable damp proof courses that do not break down, the problem can be caused by any number of factors, the majority of which can be attributed to defects in design or construction and the damp proof course has been put in the wrong place or even not at all. This can lead to the same symptoms developing as described above.
The good news is these problems can be permanently rectified by Combined Damp Solutions.

How Rising Damp is Treated


The exact extent of the damp is detected by a moisture encounter meter which works by sending an electronic current through the wall. If the wall is damp, the current will be conducted by the water in the wall and will be displayed as a reading on the machine.
In straight forward rising damp situations the process is as follows. The render or plaster is removed from the wall up to the height the damp has reached, exposing the masonry work that must be treated. 
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A line of holes are drilled into the brickwork along the base of the wall. (usually two holes per brick) A silicone based solution is then injected under high pressure into the holes using a high pressure pump. This solution penetrates through the brick and the surrounding mortar creating a permanent barrier in the wall which arrests the damp cycle.
The wall is then re-rendered with a salt resistant cement mix and, if required, replastered to match the original surface and finished to match surrounding walls. 
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Quite often however, there may be more than one cause of the problem and a number of remedial techniques must be utilised. 

Other Leading Causes Of Damp And Water Problems In Buildings


Combined Damp Solutions has treated thousands of homes around the city of Sydney. In our time we have seen a wide variety of problems that have required thinking outside the box to reach a permanent solution. Below are just some of the issues we come across. 

Leaking Waterproof Membranes Causing Moisture and Damp

Leaking waterproof membranes in bathrooms, balconies and exposed masonry can allow water penetration into the structure causing damage to plaster, paint, render, joinery units, carpet and skirtings. We see incorrect waterproof membranes being used under the wrong conditions or cheaper substitutes being used that simply do not last.

Building Movement Causing Leaks And Damp

Masonry cracks caused by structural movement over time or expansion and contraction of the building as a result of moisture and or temperature variations cause concrete slabs that were once water tight to pass water and allow it to find a way through the slab. This is the leading cause of concrete cancer and will eventually lead to complete structural failure of the steel giving the slab its strength. The process to repair this involves exposure of the effected steel and treatment with an epoxy sealer before reinstating the concrete. The extent to which concrete cancer has occured however will dictate what remedial measures must be taken. 

Incorrectly Installed Window And Door Flashings Causing Damp

Window and door flashings must be installed so that any water that finds its way under or around the frame will hit the flashing and run away from the inside of the building and exit through weap holes. 
We have seen many examples of flashing sloped towards the building allowing water to flow inside, or window and door frames that have been installed with no flashing at all. To remediate this problem the frame must be removed in order to install the flashing correctly or, if possible, remove only the bricks the frame is sitting on and install a new flashing in this way. 

Old Or Unsuitable Paints Causing Damp in Walls

Exteranl walls with old or unsuitable paint that has broken down and peeled off causing moisture to pass through the wall can lead to internal damp problems. Most walls, if built correctly have an independent external skin that will not cause any problems if it becomes wet. If the wall cavity is blocked with rubble or dirt, or it is a solid double brick wall built with no cavity then there is an oppertunity for water to reach the inside skin of the house and cause damage. 

Damp Proof Course Bridging Causing Damp

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.


Poor Drainage Behind Walls Causing Lateral Or Rising Damp

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. 


Concrete Slabs Causing Rising Damp In Walls

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. 


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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. 


Sydney's Terrace Houses And Town Houses- The Damp Problems They Experience

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.


Damp and Moisture Problems Caused By Rising Water Tables In Sydney

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. 


Damp And Water Damage Caused By leaking Balconies, verandas, Landings and Suspended Slabs

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.