2. Partitions
• Internal walls which subdivide
rooms
• Can be load bearing or non load
bearing
• Load bearing partitions can be
treated like external walls, but
without the need for rain
resistance
• Non load bearing partitions are
different
3. Finishes
• Finishes can be internal or external
• Finishes can be thick, property
changing, or thin, cosmetic.
• Some finishes are integral to the
nature of partitions, so will be
considered first.
4. External finishes
• Dry finishes – claddings
– Timber boarding
– Tile hanging
– Corrugated metal or plastic sheeting
• Wet finishes-renders
– Renders, either cement or lime
plaster based
– Paints, either cosmetic or protective
5. Dry claddings
• Hidden faces of
cladding must be
ventilated and dry
• Exposed faces must be
out of contact with
ground and allowed to
dry
6. Keep it dry
Wooden cladding: Structural wall: can be
ventilated behind, out masonry, timber
of contact with the framed or even an
ground. Best to use a open steel frame
rot resistant wood
such as western red
cedar
Ventilation: free flow
of air using battens
and gaps
7. Remedial cladding
• Insulated dry external cladding can
be fixed as a remedial measure to
thin, cold damp walls or over failed
roofs
8. Upgrading and old, cold but sound wall
Old, cold wall
Old, cold wall
New cladding on Old, cold wall
battens
Insulation behind
cladding Vapour barrier
between old wall
and warm side of
insulation
9. Wet claddings: rendering
• Rendering refers to covering an
external wall surface with a plaster
• Renders change the appearance of
a wall and can improve the
performance
• Traditional renders were lime
plaster based, but modern ones
are largely portland cement based.
11. Working with stucco
• Stucco needs to be strongly keyed
to the sub surface
– Keying can be grooves in the
brickwork, heads of partly driven
nails, or in modern work, stainless
steel meshes fixed to the sub surface
• Any lime based finish must be
protected form the rain
– Good roof overhangs
– Painted finish
12. Cement based rendering
• Modern cement based renders are
basically thin layers of concrete
• Basic rule is the render must be
weaker than the supporting wall so
that the render fails first
• Render should also be slightly
flexible
• Both achieved by concrete
admixtures, often incorporating
some lime.
14. Why render a building?
• For appearance, as on the RAC
campus
– Cheaper than natural stone
– More sympathetic than artificial stone
• Improved performance of old walls
– Rendering can cover cracks
– Extra layer can help rain resistance
– Render can cover a new layer of
external insulation
16. Plaster
• Plasters are thick,
gel like materials
applied to rough
walls to give a
smooth finish.
• Plastering is a
highly skilled
trade
• Plasters are either
traditional lime
plasters or
modern gypsum
plasters.
17. Lime plaster
• Lime plaster
– Traditional, mixture of lime (calcium
carbonate CaCO3, derived from
limestone or chalk) with sand, water
and possibly a binder like horse hair
– Highly alkaline, never sets truly hard,
very flexible and self healing
– Lime is a dangerous, irritant chemical
– Lime plasters generally used for
conservation work on historic
buildings
18. Gypsum plaster
• Gypsum is calcium sulphate (CaSO4)
and a naturally occurring mineral in a
hydrated form
• Plaster of Paris is pure gypsum
• Gypsum building plasters usually
contains sand to bulk them out
• Gypsum plasters are non-irritant, set
hard and expand slightly on setting,
taking up any shrinkage cracks
• Vast bulk of modern building plasters
are gypsum based
19. Plastering a wall
• Three stage
process
– Dubbing out
(filling hollows
and cracks)
– Base coating (12-
15mm layer
levelling wall
surface)
– Skimming (3mm
smooth finishing
coat)
20. Plastering a wall
• Three stage
process
– Dubbing out
(filling hollows
and cracks)
– Base coating (12-
15mm layer
levelling wall
surface)
– Skimming (3mm
smooth finishing
coat)
21. Plastering a wall
• Three stage
process
– Dubbing out
(filling hollows
and cracks)
– Base coating (12-
15mm layer
levelling wall
surface)
– Skimming (3mm
smooth finishing
coat)
22. Plastering a wall
• Three stage
process
– Dubbing out
(filling hollows
and cracks)
– Base coating (12-
15mm layer
levelling wall
surface)
– Skimming (3mm
smooth finishing
coat)
23. Dry lining
• Walls can be dry lined with wooden
boarding, but most common finish is
plasterboard.
• Plasterboard is one of the cheapest but
most versatile building materials.
• Basic plaster board is a set layer of
gypsum plaster covered with strong
paper
• Plasterboard can also be foil backed as
a vapour check or foam insulation
backed as a complete internal insulation
and finishing system
25. Foam backed plasterboard
• Foam backed
plasterboard will
insulate effectively
• Boards must be
secured
mechanically as well,
i.e. with nails or
screws, to prevent it
falling off in a fire.
26. Finishing plaster board
• Joints covered in fabric tape and
thin layer of plaster
• Whole surface covered in a thin
skim coat 3mm thick
27. Partitions
• Load bearing partitions generally
built in blockwork with a
plaster/plasterboard finish
• Non load bearing partitions
– Timber framed with plasterboard
finish both sides
– Laminated plaster board
– Steel studwork with plasterboard
finish
44. Thin finishes
• Thin finishes can be classed into
opaque (paints) or transparent
(varnishes).
• Staines are not a true finish, but
change the appearance of timbers
and have water repellent and anti-
fungal components.
45. Paints
• All materials can be painted to
– Improve appearance
– Change colour
– Protect base material
• Paints always applied as a system
– Primer: acts as a glue between base
surface and paint system
– Undercoat: highly pigmented, forms
body of the system
– Top coat, usually impermeable, may
be glossy, gives final colour and seal
46. Varnish
• Transparent finish
• Only used on wood
• Primers and undercoats can’t be
used because of transparency
• Multiple layers needed
• Usually requires refinishing a
regular intervals particularly if
exposed to sunlight
47. Stains
• Pigmented, largely transparent
chemicals with water repellent and
fungicidal qualities
• Designed to soak into timber and give it
a weather resistant, coloured surface
• Works well for exposed structural
timber, such as fences
• Much used for window frames in the
1970-80s with poor results. Water still
gets into the joints
• Easy to restain, hard to refinish with
paint
48. References
• Lafarge are the largest plaster and
plasterboard manufacturers and
produce very good technical
literature:
• www.lafarge.co.uk
• Lafarge dry lining manual
– http://www.lafargeplasterboard.co.uk
/drywall_manual/default.html
• Any building textbook will give
details of internal plastering and
partitioning systems