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Ventilation -

Due to lack of building regulations, and need for airtight, energy efficient buildings, ventilation is lacking. Increased condensation has allowed for a greater frequency of mould.


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A major cause of mould build up is the result of poor or idadequate subfloor ventilation. Once relative humidity levels within the building exceed 60%, mould will gdevelop. A damp subfloor will also provide ideal conditions for termites and timber decay. It is essential to have adequate airflow. This requires sufficient air entering and exiting the subfloor(crossflow ventilation). Increased crossflow will promote drying and a healthy environment.

Subfloor vents require inspection and cleaning if required. Additional vents may be installed if adequate crossflow is possible. Existing passive vents can be replaced with more efficient designs. This will allow greater inflow of fresh air and outflow of stale air. Where there appears to be sufficient vents but crossflow ventilation is not being achieved. Forced ventilation in most cases will remedy this problem.

Low voltage ventilation fans 12V can prove affective in small areas and where access to subfloor is restricted. The benefits of this ventilation system are relatively low installation costs, low noise and running costs. As this system is low voltage it is unable to remove larrge volumes of air so it is restricted in it's application.

Alternatively an inline centrifugal subfloor ventilation fan which operates on 240V can function under more testing conditions. With the installation of ducts this system is a more targeted approach to creating affective crossflow. The downside higher installation costs, higher noise levels and running costs(similar power usage to a 75W lightglobe). The fan is set on a timer and operates only during daylight hours.

If the subfloor is being used for storage or there is a build up of building debris this may be restricting airflow. Heating systems which use large ducts should be avoided. In some cases ducted heating can be replaced with a hydronic system. Removing excess soil from subfloor should be avoided as this can create an area for water to pool.

In addition to subfloor ventilation it is important to ensure that water levels are kept to a minimum. Finding the source of any moisture problems and fixing any leaks is essential. Leaking downpipes and gutters, blocked stormwater drains are common sources and can significantly increase moisture levels subfloor. Installing a perforated plastic pipe(aggie) will not only remove excess surface waterbut can help reduce ground water levels. The building may have a rising damp issue, this requires expert diagnosis. Rising damp can be a moisture source for mould to develop.

Lastly the building may be located in an area that is prone to flooding. A prvention pan that restricts the ingress of water should be considered. The ability to open and close vents and doorways when flooding commences. Brickwork, stonework, render can be coated with a water repllant that will prevent saturation of the building fabric. A good quality repellant(Stormdry) will last at least 20-25 years. All defective mortar should be reinstated.
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