recommended sub-floor detail:  brick veneer homes

disconnecting the wall cavity

The thermal performance of timber floors in brick veneer construction can be readily improved by eliminating the cavity airflow path at either the roof or floor.

A 'flashing' across the wall cavity controls the airflow between the roof space and sub-floor, effectively disconnecting the roof space from the sub-floor space.

This change will directly improve the House Energy Rating of a design with an enclosed sub-floor by at least 0.5 star. Make the change in either the roof or sub-floor area by taking flashing from the brickwork to the top- or bottom-plate. With the bottom-plate option you will need to insert weep holes for removing condensation – as with slab on ground construction. Another way is to fold over and secure foil across the cavity gap at the top of the brickwork. Part of floor insulation, especially for cool zones, is looking at restricting air-flow in the sub-floor space, by enclosing the area while still allowing enough air movement for healthy ventilation.

In more temperate zones being off the ground has the advantage of helping the house cool quicker if air can move freely underneath, as in the traditional Queenslander house model.

To learn more, read the FWPRDC publication Insulation solutions to enhance the thermal resistance of suspended timber floor systems in Australia. 1.26 MB

For information on adequate vents and sensible floor vent placement, see Building Code of Australia Volume 2 Part 3.4.1.