CONCRETE AND SUSPENDED TIMBER Ground Floors CONCRETE AND SUSPENDED TIMBER

TYPES OF GROUND FLOORS Concrete Suspended timber Ground floors

FUNCTIONS Support imposed loads Provide a level surface May differ depending what the building is used for Factory floor needs to be capable of supporting larger loads than that of a dwelling house Machinery/vehicles Partitions/furniture People Provide a level surface Strength and stability Durability The material used remain intact surface of floor does not ravel Quality of concrete

FUNCTIONS Prevent damp rising Prevent heat loss Allow for finish As a concrete floor rests on the ground dampness can rise up through it due to capillary action the use of a damp proof membrane can prevent this happening Prevent heat loss Allow for finish

CONCRETE GROUND FLOOR: COMPONENTS Hardcore Crushed stone dia. 100mm Layers 225mm deep Max. Depth 900mm Insulation 60mm expanded polystyrene Damp proof membrane 1200 gauge plastic sheet Laid on sand blinding Concrete 1:3:6 mix

FOUNDATION & RISING WALLS soil Concrete foundation

HARDCORE PLACED & COMPACTED 150mm min. hardcore

DAMP PROOF MEMBRANE dpm carried up wall and over block work of inner leaf

INSULATION 25mm insulation 60mm insulation

REINFORCED CONCRETE SLAB 150mm min. concrete

WALLS CONSTRUCTED 150mm min. clearance

FLOOR OPTIONS The services can be laid in the concrete slab in advance This will negate the need for a finished slab It will however mean that there will be a reduced flexibility in dealing with services afterwards Changes in the service layouts cannot be made without digging up the floor With the inclusion of the finish screed service plans can be altered even after the walls are built

OPTIONAL SCREED A 75mm screed can be placed on top of the floor to accommodate service pipes such as central heating and gas

RISING WALLS COMPLETED

HARDCORE INFILL

RADON BARRIER LAID

DPM / INSULATION /STEEL

CONCRETE POURED

POWER FLOATING CONCRETE

CONCRETE GROUND FLOOR: FINISHED

CONCRETE GROUND FLOOR: FINISHED

ALTERNATIVE METHOD Components: Hardcore Concrete subfloor Dpm Insulation Concrete screed (cement & sand mix)

CONSTRUCTION DETAILS screed insulation dpc/dpm slab hardcore

FUNCTIONS OF SCREED Provide a level surface for finish Carpet / Tiles / Timber Take out any irregularities in the slab Accommodate services Pipes

ALTERNATIVE METHOD Advantages Disadvantages Screed laid after heavy work No need to protect floor during construction Dpm less likely to be damaged Disadvantages Dpm not continuous from floor to wall Screed must be barrowed in Labour intensive / costly

SUSPENDED TIMBER FLOOR

When is a suspended timber floor best used? Used where the depth of fill exeeds 900mm. 900mm

Underfloor Ventilation Why do we need ventilation? To avoid excessive build up of moist air in the underfloor space. To keep the moisture content of the timber floor members below 20% of their dry weight, to prevent fungal attack taking place.

Dwarf wall Wall plate underside treated DPC Block sleeper wall 150mm gaps Gaps left between blocks to allow air circulation 150mm

How to calculate the number of ventilations opes required, for the house illustrated.

150mm seated vent through cavity DPC GL Radon Barrier 100MM Insulation 22mm Timber floor 125 x 44 Timber Joists DPC 100 x 75mm wall plate on DPC Min 75mm For ventilation Min 150mm Dwarf Wall span 2m between 150mm Concrete slab GL 150 Radon Barrier 150MM LAYER OF HARD CORE T `3T