Floors construction

1. After the foundations have been completed and the external walls constructed the construction of the floors commences. Floors construction

2. Function of a ground floor • To carry loads imposed on them. • To prevent dampness rising from the ground into the building. • To provide a degree of thermal insulation. • To prevent growth of vegetable matter in the building. • To provide a suitable wearing surface. Basically there are two types of ground floors:- solid floors and suspended floors.

3. Solid ground floor One in which the whole floor area is in contact with the subsoil. Comprised of three main components:- • Hardcore The purpose of this is (a) To ensure consistent material over the whole floor area. (b) To reduce capillary action of moisture from the ground because of voids within the hardcore layer. (c) To make up levels after removing topsoil and reduced level excavation. (d) to provide a clean dry and firm working surface. The top of the hardcore should be blinded with a fine dust or sand to fill the voids, prevent grout loss from concrete and protect D.P.M. if placed in this position.

4. Solid ground floor Damp proof membrane (DPM) An impervious layer to prevent moisture travelling through the floor to the inside of the building eg. polythene sheeting. Concrete bed This provides the solid level surface to which screeds and finishes can be applied.

5. Floor detail at junction with a cavity wall 1200 gauge polythene DPM Skirting 50 mm min Insulation Sand and Cement screed Sand and Cement screed DPC 150mm minimum above Ground level 100mm Concrete sub floor Ground level Hardcore

6. Timber floors • Suspended timber floor joists are supported by the walls which transfer the load from the floor, through the wall to the foundations. • The traditional method of providing a flooring surface on top of these joist’s was sawn timber boards which had square edges. These boards were butted together and nailed down unto the top of the joist. • The quality of the flooring boards was improved by the addition of tongue and grooved joints. Supporting wall Square edge flooring 150mm wide and 20mm thick. Floor joist Supporting wall

7. Timber ground floors • If timber ground floors are used ventilation must be provided beneath the floor construction. The reason for this ventilation is to prevent the moisture content of the timber rising above an unacceptable level (ie. 20%) which would create the conditions for possible fungal attack. • Sheet materials such as plywood and chipboard are now the most popular coverings to floor joists. The most common size of sheets are 1220mm x 2440mm. • Floor joists are usually placed at 400mm centres. Joist spaced at 400mm centres. Plywood sheeting Positions for ventilation

8. Suspended T beam concrete floor Pre-stressed concrete floor beams cast in the shape of an inverted T Concrete blocks laid between T beams 100mm sand and cement screed on top of beam floor Pre-stressed concrete floor beams Pre-stressed T beam concrete floors were one of the first methods of creating suspended concrete floors. The beams were set in position in such a way that a 450mm concrete block fitted neatly between the beams. The load of the floor was transferred to the foundations by the beams.

9. Suspended concrete floors • HomeSPAN is the trade name for a suspended concrete flooring system which has recently been developed for the domestic market. • This flooring system comprises of flat precast concrete planks generally 600mm wide and 150mm deep. It can carry domestic loadings up to 5m clear span. • These concrete floors have excellent sound insulation and fire resistance. • After settlement, cracking is dramatically reduced as most cracks results from the shrinkage of timber joist. Suspended concrete flooring slabs. Walls constructed to support floor slabs.