The Victorian Bushfires Royal Commission has demanded new national guidelines for bushfire bunkers be ready by April - one of a host of recommended changes to building standards in fire-prone areas.

In its second interim report, tabled to the state parliament on Tuesday, the commission said there is a strong case for immediate revision of construction requirements in areas at risk of bushfires.

Citing evidence given by Commonwealth Scientific and Industrial Research Organization (CSIRO) scientist Justin Leonard, the commission said it wants the standards changed relating to buildings on unmanaged grassland, and increased ember protection for properties classified as being at low risk of bushfire attack.

At present unmanaged grassland is not considered when assessing a site's bushfire attack level, except in Tasmania.

Leonard told the commission evidence from recent fires highlighted the significant risks buildings face from grassland fuels.

"There seems to be no reason for this issue not to be dealt with by an immediate amendment to the building code," the commission said in its report.

The commission has ordered Standards Australia to report to it on the progress of amendments to the building code to boost ember- protection measures for properties at low risk of bushfire attack, especially in regard to sub-floor requirements and materials prescribed for doors, windows and wall barriers.

The Australian Building Codes Board has committed to releasing a standard for bushfire bunkers no later than April 30, 2010.

The standard will address factors such as fire and high wind resistance, structural strength, minimum size and maximum occupancy.