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Ground Floors. CONCRETE AND SUSPENDED TIMBER. TYPES OF GROUND FLOORS. Concrete Suspended timber. Ground floors. FUNCTIONS. Support imposed loads 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
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Ground Floors CONCRETE AND SUSPENDED TIMBER
TYPES OF GROUND FLOORS • Concrete • Suspended timber Ground floors
FUNCTIONS • Support imposed loads • 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 • 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 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
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 • 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
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.
Wall plate underside treated Dwarf wall 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. 10m 6m
T 100MM Insulation 50 100 100 100 150mm seated vent through cavity 22mm Timber floor 125 x 44 Timber Joists 100 x 75mm wall plate on DPC DPC Dwarf Wall span 2m between Min 75mm For ventilation Min 150mm 150mm Concrete slab Radon Barrier GL 150 150MM LAYER OF HARD CORE T `3T