After the foundations have been completed and the external walls
constructed the construction of the floors commences.
Floors construction
Function of a ground floor
1. To carry loads imposed on them.
2. To prevent dampness rising from the
ground into the building.
3. To provide a degree of thermal insulation.
4. To prevent growth of vegetable matter in
the building.
5. To provide a suitable wearing surface.
Basically there are two types of ground floors:solid floors and suspended floors.
Solid ground floor
One in which the whole floor area is in contact with the
subsoil. Comprised of three main components:1. 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.
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.
Floor detail at junction with a
cavity wall
1200 gauge polythene DPM
Skirting
Sand and Cement screed
Sand and Cement screed
50 mm min Insulation
DPC 150mm minimum
above Ground level
Ground level
100mm Concrete sub floor
Hardcore
Timber floors
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Suspended timber floor joists are
supported by the walls which
transfer the load from the floor,
through the wall to the foundations.
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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.
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The quality of the flooring boards
was improved by the addition of
tongue and grooved joints.
Supporting
wall
Floor joist
Square edge
flooring 150mm
wide and 20mm
thick.
Supporting
wall
Timber ground floors
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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.
Joist spaced at
400mm centres.
Plywood
sheeting
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.
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Floor joists are usually placed at
400mm centres.
Positions for
ventilation
Suspended T beam
concrete floor
Concrete blocks laid
between T beams
Pre-stressed concrete
floor beams
100mm sand
and cement
screed on
top of beam
floor
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.
Pre-stressed
concrete floor
beams cast in
the shape of
an inverted T
Suspended concrete floors
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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.