Bearers and joist
Most newer #houses are #built on #concrete slabs, most older #homes are #built with a #timber floor using #bearers and #joists.
Commonly we are #adding #homeextensions to older #homes hence the timber #floor. Traditionally #Australian homes use #hardwood for the sub floor timbers, these days we most commonly use #engineered #timber like seen here. The engineered timber is straight with no #knots does not shrink, comes in long #lengths and are #termite #treated.