1. Floors
Structure and finish

2. Floors: the basics
• Two fundamental types:
– Ground floors, which form part of the
external enclosure
– Upper floors, which subdivide the
internal space
• The ground floor can either be
“floating” (supported by the
ground) or “suspended”, supported
by the walls at the edges.
• Upper floors are always suspended

3. Floor support
Suspended upper
floor: held up by
walls
Floating ground
floor, resting on
the sub-soil

4. Floor support
Suspended upper
floor: held up by
walls
Floating ground
floor, resting on
the sub-soil

5. Floating ground floor
• Several functions:
– Level, smooth structural surface to
support furniture etc.
– Damp exclusion
– Insulation from the exterior
• Most common type of floating floor
is a multilayered insitu-concrete
floor. Often referred to as a “solid
floor”

6. Relationship of floor to wall
Top 50mm of fill is
Fill: topsoil and loose sand blinded to form
subsoil removed and smooth surface
replaced with
compacted hardcore
(broken stone or
brick)
Floor
Min 150mm
Fill
Ground

7. Views of floor preparation
Ready for hardcore Sand blinding

8. Water exclusion: damp proof membrane DPM
Essential link between
DPM and DPC
Damp proof membrane: usually
plastic sheeting. Seams sealed or
very well overlapped

9. The concrete slab itself, poured insitu
Slab 100-150 mm thick, poured in
one go. Allowed to cure, kept
damp
Floor
Fill

10. Smooth surface finish
• Insitu concrete very
rough
• Smooth finish often
achieved with 50mm
sand/cement screed
• Screed is applied
when concrete is set
but not fully cured
• Surface is trowelled
smooth.

11. Floor layers
Decorative finish: carpet, tile wood, etc
50mm smooth screed
100mm insitu concrete
Damp proof membrane
50mm sand blinding
Compacted hardcore,
maximum depth
How to insulate? 600mm

12. Insulate above slab
Decorative finish: carpet, tile wood, etc
15mm chipboard layer
75mm expanded
polystyrene
100mm insitu
concrete
Don’t use above slab insulation with below floor heating…

13. Insulate below slab
Decorative finish: carpet, tile wood, etc
50mm smooth screed
100mm insitu
concrete
DPM can be above or
below insulation
75mm closed cell,
high density,
expanded polystyrene
Very effective with below floor heating

14. Suspended ground floor
• If fill needs to
be more than
600mm
• If high speed
construction is
needed Beam and block: Beams are
pre-cast, reinforced concrete,
• Precast laid on the dpc and built into
concrete walls at ends.
suspended Finished with insulation and
floors can be chipboard
used.

15. Expanded polystyrene block and beam floor
Proprietary “Jetfloor” Polystyrene “blocks”
supported by beams and topped with a reinforced
screed

16. Upper floors
• Always suspended
• Nearly always built of timber like a
flat roof
– Joists (multiple parallel beams)
– Floor boards on top (usually sheets
materials like plywood or chipboard)
– Ceiling below (usually plasterboard)
• No need for thermal insulation, but
may incorporate sound insulation

17. Timber suspended upper floor
Galvanised steel joist hanger

18. Timber suspended upper floor
Softwood joists @ 600 centres
Galvanised steel joist hanger

19. Timber suspended upper floor
Chipboard flooring. (Plywood
in wet areas)
Softwood joists @ 600 centres
Galvanised steel joist hanger

20. Timber suspended upper floor
Chipboard flooring. (Plywood
in wet areas)
Softwood joists @ 600 centres
Plasterboard ceiling
Galvanised steel joist hanger

21. Joist detailing 1
Joists braced at 2.5m centres by strutting
Joists overlapping over supporting
internal wall
Joists supported by
joist hangers to a
major structural beam

22. Joist detailing 2
Here the joists are
resting directly on
supporting walls and
are braced with solid
blocking pieces
Waferboard flooring being laid

23. Forming openings
Trimmer
Doubled joist
Large opening essential for the staircase

24. Plasterboard ceiling
Plasterboard: gypsum
plaster between layers of
strong paper
Boards nailed to joists
Nail heads plastered over
Joints between boards filled with thin
strip of wet plaster
Whole ceiling will be given a 3mm skim
coat of finishing plaster

25. References
• CHUDLEY, R. ; GREENO, R.
(2005). Construction technology.
4th ed. Pearson Education.
CHUDLEY, R. ; GREENO, R.
(2006). Building construction
handbook. 6th ed. Butterworth-
Heinemann.