While the upper floors of a house are usually constructed of timber, the ground floor may be made of timber or it may be of solid concrete. In most modern buildings of today it will be solid concrete or perhaps block and beam. If your house was built before 1939, it is likely to have the former, but after that time it will probably have the latter.
Suspended Timber Floors
All timber floors are based on the same method of construction with minor differences. They have a supporting framework of timber beams called joists to which are nailed timber boards or chipboard panels. The joists of timber ground floors are supported at their ends and sometimes at one or two points in between – on additional timber beams known as wall plates. These in turn rest on the tops of low brick sleeper walls.
These sleeper intermediate walls are not solid but are laid in honeycombe fashion with spaces between the bricks to allow the air to circulate below the floor to prevent condensation and rot forming. For the same reason, ventilators (air bricks) are usually fitted at the base of the external walls and must always be kept clear. Slates or strips of flexible DPC material are laid between the wall plates and sleeper walls to prevent damp attacking the wood.
Sometimes the joists have been know to be are laid on top of individual bricks set on the ground. Upstairs, the joists are also supported by wall plates but these can be held by metal brackets called joist hangers, which are cemented into the walls. Sometimes also, the joist ends may be set in sockets between the bricks, with a metal plate below to spread the load through the wall. A typical joist dimention for an upstairs floor joist in a domestic dwelling in modern days is 9 x 2 or in metric 225 mm x 50 mm.
As construction has moved on in later years, design and methods of building have changed in many ways. Years ago, it would be unthinkable to have a concrete floor above ground floor level where as now, most modern buildings are constructed in this way; Particularly commercial developments etc.
In a later post we will look at concrete floors, their construction, and benefits.