Systems Building Maintenance
Building Maintenance 'done right the first time'

Rising Damp

Masonary Damp. 

What is Rising Damp?

Rising damp is naturally occurring in most masonry structures.  

The source of true rising damp is capillary action due to ground moisture migrating through the internal pores or voids of the masonry, bringing with it contaminating ground salts in the solution.

The characteristics to look for when diagnosing rising damp are usually:

  • salt deposits,
  • fretting or spalling bricks,
  • fretting mortar,
  • deteriorating wall plaster, and
  • flaking paint with visible surface salt.

Causes of Rising Damp

Rising damp can be caused by the bridging of mortar debris in the cavity walls.  These mortar droppings can create a bridge for moisture and a direct path to the internal walls.  This can only be rectified by removal of bricks from the base of the wall at intermittent intervals so the wall cavities can be raked clean.  This also increases the cavity ventilation.

Another cause of rising damp, is poor sub-floor ventilation.  Improved sub-floor ventilation is helpful in prevention.  Vents should be installed to provide a good cross-flow of air throughout the underfloor area of the building and so increase evaporation. 

It is important that all other sources of dampness be eliminated in the initial examination.  For example, bridging of external damp courses through garden beds, condensation, ponding water through downpipe discharging, roof and window flashings.

Over the years, misunderstood treatments of rising damp have had detrimental effects on some period buildings.  For example, the introduction of concrete floors and external wall render have reduced the evaporation from masonry walls.

Contributing Factors

The removal of external render, especially in limestone or random rubble construction can be sometimes an instant cure for rising damp, along with all making good of other contributing factors, such as:

  • garden beds;
  • insufficient sub-floor ventilation;
  • weathered window sills;
  • external render bridging damp proof course;  or
  • stormwater discharging onto ground.

Chemical Damp Coursing

Two Alternative Chemical Solutions to Damp

Systems Building Maintenance offers two alternative chemical solutions to rising damp problems depending on the type of construction.

 1.  Pressure Injection Method

Depending on brick suitability 3 holes 10 mm in diameter at approximately 75 mm centres are drilled at floor level.  The fluid is then injected under pressure via specialised injection rods, until the brick and surrounding mortar is saturated by the injection fluid creating a damp proof course at floor level. 

Certain factors can contribute to some of the bricks being unsuitable for injection due to spalling and breaking during the drilling process or removal of dense wall plaster.  These bricks will be marked and then removed and replaced. Removal of perpendicular joints along the injection line is occasionally required.

Injection Fluid

Damp course fluid is manufactured by Rhone Poulenc, world-renowned chemical manufacturer.  It is a potassium methyl silliconate known as 51T.  Its function is to make the capillary network in the material water repellent.  This occurs through polymerisation of the product in contact with carbon dioxide present in the material. 

2.  DPC Cream Method

Lectros DPC Cream is a highly effective alternative solution to rising damp problems.  Lectros DPC Cream is a unique silicone emulsion cream for injection into damp masonry for the control of rising dampness. Lectros DPC Cream can be used in all types of masonry, depending on the moisture content of the structure.

The Lectros DPC Injection Cream is delivered by a specialised pressure injection pump with an injector lance into a series of 12mm holes.  The cream is injected into the mortar course, where it transfers rapidly into the damp masonry pores.  Here, the injection cream reverts to a liquid phase and polysiloxanes are formed. 

The chemical reaction and forming of the DPC process takes approximately 2 – 6 weeks, depending on the wall thickness.

This is the fastest damp course installation method, however this process requires a quite high moisture content to be successful.

Lectros DPC Cream is guaranteed for twenty years when installed according to the manufacturer’s instructions by an authorized installation contractor.


Lectros Electro Osmosis

The Lectros Electro Osmotic System is not a masonry capillary coating or blocker, but a proven active method of reversing the moisture's natural electric potential, which originates when water rises in a masonry wall. 

Put simply, it drives the damp out of your walls!

Is this System Safe?

If your choice to rectify damp is "chemical free", the Lectros System is for you. It is fast working, safe, simple and 100% effective.  In fact Lectros provide a 30 Year Guarantee and is CSIRO approved.

The Lectros System is suitable for any type of masonry, clay brick, sandstone, limestone, rubble filled, aerated concrete, precast concrete - even mud brick dwellings!

How does the Lectros System Work?

Through a series of platinised titanium rods inserted into the masonry about a metre apart, a very small and perfectly safe electric current is introduced into the wall just above ground level, (mA range).  This current repels the rising moisture molecules and dissolves salts down the walls harmlessly back into the ground.  Just as “poles” of magnets repel or attract each other, the positively charged mobile moisture molecules are repelled from the positive anode and attracted to the negative cathode. 

As long as this tiny positive charge is maintained your walls are protected from rising damp. 

By repelling excess moisture below timber floor structures down into the soil, the Lectros System fulfils the true requirements of a damp course and costs less to operate than a door bell.

This system minimises the need to remove sound plaster or render as most dissolved hydroscopic ground salts are carried back down into the soil.

How do I know the Lectros System will do the job?

  • The Lectros System has received CSIRO Appraisal through Technical Assessment #308. 
  • The Lectros System has a 30 year guarantee
  • It is a proven, century old method with scientific principles
  • Approaching 100,000 Projects worldwide.
  • Independently “on-site” tested in Australia by AMDEL Ltd. 

Condensation as the name suggests is water which has “condensed” from warm, moist air on contact with a cold surface.

Air holds water in the form of water vapour (moisture).  Warm air is able to hold more moisture than cold air.  Air which contains its maximum moisture content is said to be saturated.  Roughly speaking the amount doubles for every 10ºC rise in temperature. 

 

Condensation & Associated Problems

 
The amount of moisture in the air is usually expressed as Relative Humidity (RH).  Saturated air is said to have 100% RHThe RH of air with a particular moisture content will vary with temperature, so as the air is cooled its relative humidity will increase.

The amount of moisture in the air is usually expressed as Relative Humidity (RH).  Saturated air is said to have 100% RHThe RH of air with a particular moisture content will vary with temperature, so as the air is cooled its relative humidity will increase.

 
Below 9ºC the air in the above example would be incapable of holding any more moisture and the surplus would be released as condensation.  The temperature at which this occurs is known as the Dew Point and is dependent upon the amount of moisture in the air.  The higher the moisture content the higher the Dew Point.

Below 9ºC the air in the above example would be incapable of holding any more moisture and the surplus would be released as condensation.  The temperature at which this occurs is known as the Dew Point and is dependent upon the amount of moisture in the air.  The higher the moisture content the higher the Dew Point.

 

Why is this relevant to rising damp?

Condensation in dwellings usually progresses through the house as condensed moist air and is usually attracted to the coldest surfaces in the house.  In Western Australia, this is usually the southern end, or most shaded end of the house. 

Condensation usually shows its presence on the cold surfaces such asglass where it is most prominent and can also be found in the least ventilated areas such as walk-in wardrobes, cupboards etc. 

In many circumstances, this condensation problem can be confused with rising damp at low levels and roof leaks in ceilings.


Why do I need a damp proof course?

A damp proof course is solely designed to stop moisture rising from the ground into the walls, directly above ground level.  Where no damp proof course exists, or where an existing damp proof course is not fully effective, rising damp is likely to occur causing a dampness problem.

In such situations the installation of a damp proof course into the walls at the correct level will prevent further rising damp.  Irrespective of the type of damp proof course used eg chemical or physical, current dampness may to continue to be a problem due to:

(a) residual moisture in the walls

(b) the action of hygroscopic salts

In time residual moisture will dry out but dampness caused by the presence of these salts within the wall and wall plaster may continue to give problems even though all other sources of moisture ingress have been rectified.

Salt Deposits

As moisture rises from the ground into a wall, it carried with it soluble ground salts which are deposited in the wall fabric and wall plaster as the moisture evaporates.

Certain of the soluble salts carried up from the ground by rising damp and in particular chlorides and nitrates are hygroscopic, that is they will attract moisture from the atmosphere.

Where dampness continues to rise into a wall for a substantial period the deposit of hygroscopic salts built up may be sufficient to cause a significant dampness problem particularly at periods when the relative humidity of the atmosphere is high.

Rectification of Dampness caused by Salt Contamination

Wall plaster affected by hygroscopic salts should be removed and the wall replastered using a plastering system that does not readily allow any salts within the wall fabric to migrate to the surface of the new plaster.

When to Replaster

Systems Building Maintenance recommends that replastering should be delayed for as long as possible.

By delaying replastering, time is allowed for soluble salts to move from the brickwork into the old plaster. In addition, if replastering can be delayed until after residual moisture has dried out, the true extent of dampness caused by hygroscopic salts may be more easily established and it may be possible to restrict the extent of replastering.

Where early redecoration is required following damp proof coursing replastering can, in the majority of cases, be carried out shortly after the completion of the damp coursing work.

In such cases the plaster work must be able to hold back hygroscopic salts during the drying out period. Any waterproofing additives used must be of a type to permit the passage of water vapour.

Redecoration

To prevent further problems,Systems Building Maintenance recommends wall plaster be allowed to dry out thoroughly before any redecoration is undertaken.

Plastering After Rising Damp