Underfloor Ventilation

  • Description

With increase insulation standards within our homes, an increase in condensation problems can occur if proper ventilation is not provided. One of the areas to be ventilated is the crawl space or the space below the floor. Where a ground bearing concrete floor exist this requirement is not necessary.

Therefore this requirement applies to timber floors and suspended concrete floors only. Moisture and gas from the ground can seep into the area under the floor. Hazardous subsoil gases can build up within the space and leach into the dwelling. Gases such as radon and methane are dangerous to our health so their dispersal into the atmosphere is much more beneficial than letting them buildup within the dwelling.

Moisture in the floor void is also harmful to our health as well as harmful to the dwelling. When moisture builds up under the floor, absorption of the moisture by the floor timbers will start to begin, over time the timbers will become saturated with moisture and mould growth will start, then wet rot will take hold. Then it’s just a matter of time before the floor timbers begin to fail.

With hazardous radon and methane gases and mould spores forming under the floor, good under floor ventilation is essential for the health of the occupants.

The method of ventilating is by vent ducts through the external walls under the floor known as vent bricks they should be located on either side of the dwelling at 3000mm centers but to prevent areas of stagnate air pockets the vent bricks should be placed at 2000mm centers.

There may be internal walls under the floor that support the floor joists and other internal walls, these walls must be of honeycomb construction to allow the free flow of air, so that the gases and moist air is expelled from the building.