SEHH/SEHS2330

Construction Technology and

Material 1

Finishes to Buildings

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Finishes
 “Finishes” is a about the decorative surface of
buildings (at walls, floors and ceilings)
 Finishes provide the provide appearance of
building (internal and/or external)
 As decorative surfaces of buildings, finishes aim
to provice suitable and pleasing surfaces for
prescribed activities and/or functions
 Sometimes, finishes may also be required to
achieve other functions, e.g., sound insulation,
thermal insulation, fire resistance, etc.
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Learning Objectives
 Able to
 Define the functional requirements
 Appreciate nature, applications and constraints of
different type of finishes

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Choosing appropriate finishing materials
 The performance criteria may be considered in selecting
appropriate finishes:
 Appearance
 Cost – initial, running & replacement costs
 Durability
 Ease of cleaning (self-cleaning)
 Ease of laying
 Impermeability to moisture penetration
 Resistance to chemical
 Resistance to dirt and staining
 Resistance to impact and abrasion
 Resistance to oil and grease
 Warmth (floor finishes)
 Resilience (floor finishes)
 Free from Slipperiness (floor finishes)
 Other functional requirement (e.g., acoustic, etc.)

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Classifying Finishes
 By the surface receiving finishes
 External Walls
 Internal Walls
 External Floor Slabs (open space / flat roof)
 Internal Floor Slabs
 Ceilings

 By the methods of applying the finishes

 In-situ applied finishes
 Plastering, paint
 Tile / Film finishes

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 In-situ Applied Finishes
 In-situ finishes refers to finishes apply direct onto the surface and
form a joint-less monolithic finishing surfaces.
 The materials for in-situ application are basically cement and sand
 Normally in-situ applied finishes are for preparing the surface for
final decorative surface
 However, by varying ingredients, in-situ can produce different
surface appearance and texture and can be adopted as final
finishing surfaces
 Typical examples of in-situ applied finishes:
 Plastering/rendering for wall
 Screeding for floor
 Pebble Stone Washed Plastering
 Granolithic Floor Screeding (with granite chippings)
 Terrazzo or Shanghai Plastering (with coloured cement and marble
chippings)
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Preparation for in-situ applied finishes
 Before applying in-situ applied finishes, the surface
(background) to receive the finishes must be
prepared so as to ensure the bonding between the
background and the finishes.
 In short, the background should be:
 Rigid
 Dried up (properly cured for concrete surface)
 Free from oil
 Free from grease
 Free from paint
 Free from dust
 Free from efflorescence
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Plastering / Rendering (walls)
 Plastering – Internal walls
 Rendering – External walls
 The general properties of plastered surfaces:
 Basically cement/sand with water for hydration reaction
 Since the plastered layer is thin, its contribution to thermal
insulation are small
 Unless special plaster are used, plastered surface only provide
limited sound insulation
 Plasters do not support combustion and evolve smoke
 For gypsum plaster for internal walls, it should not be subjected
to temperature over 430C
 Plaster are alkaline in nature, they should be dried out completely
before applying any further layer of finishes on top
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Plastering / Rendering
 To enhance bonding, “Spatterdash” (weak
cement/sand paste splashed on wall surfaces) are
usually applied onto the background (usually wall
surface) for providing better “key” to the finishes
 For junction between two different backgrounds (e.g.,
concrete & brickwork), “metal lathing” should be
fixed onto the junction areas to prevent cracking on
the plastered surface due to differential settlement

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Spatterdash

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Metal
Lath
Rendering
 Since rendering is exposed to the external environment, it implies that
it is subjected to more severe thermal, drying and moisture movements,
and hence it has a higher cement content (stronger paste) compared to
internal plastering
 Content of external rendering may include the followings:
 Ordinary / Rapid Hardening Portland Cement (OPC / RHPC)
 Sulphate-resisting Portland Cement (for severe exposure)
 Limes (for final coat)
 Sand
 Water
 In Hong Kong, since rendering surfaces will be further covered by other
finishing materials, therefore, smoothness is not of great concern, and
hence simple 1:3 cement:sand rendering is most popular

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Rendering
 One coat of rendering is not strong enough to
withstand the exposures, therefore “two-coat
application” is the common practice.
 The two coats:
 Undercoat (or Base Coat)
 Final Coat
 For rendering to be covered up by other finishing
materials (e.g., tiles), one coat may be sufficient.
 The thickness of the rendering coats:
 Undercoat: around 10-16mm
 final coat: 6 to 10mm

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Plastering
 For plastering, common constituents include:
 Gypsum (calcium sulphate)
 Portland Cement
 Lime
 Sand
 Others, e.g., fibres (to enhance bonding)
 Water
 Gypsum and lime in plastering produce good surface
smoothness. However, the problem of shrinkage (especially for
lime) should be taken into due consideration.
 On the thickness of coats for plastering, normally the aggregated
thickness for undercoat and final coat should not be more than
15mm.
 Spatterdash may be necessary to provide better bonding. The
undercoat is usually cement based, where the final coat usually
contains gypsum for achieving smoothness.
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Alternative to Plastering
 Plasterboards or Gypsum-boards are solid or
cellular gypsum plaster boarding which may
contain fibres for reinforcement.
 Plasterboards can be fixed on frame or
concrete surface directly by simple nailing.
 They are self-decorated and readily prepared
for further decoration, and are becoming
substitutes to the more expensive (higher
labour cost), time consuming and dirty “wet”
plastering process.
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 Screeding (Floor)
 Screeding is primarily a surface coating onto the structural deck.
The principal purposes of screeding include:
 To provide a smooth and level surfaces for activities and/or
further decoration.
 To raise level
 To provide fall for surface drainage
 To accommodate surfaces
 To provide thermal and/or sound insulation
 Screeding is usually in 1:3 cement:sand paste.
 For thick screeding (over 30-40mm) small amount of
coarse aggregate may be added to provide better
durability.
 Screeding can also be in the form of light-weight (air-
entrained) concrete to provide thermal insulation
performance
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Screeding
 The thickness of screeding is determined by the form
of contact between the screeding and the structural
deck.
 The thickness of the screeding is also determined by
the required functions of the screeding layer
 The common forms of floor screedings:
 Monolithic screeds (on green concrete)
 Bonded screeds (on hardened concrete)
 Unbonded screeds

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Screeding
 Monolithic screeds (on green concrete)
 A screed lay on a concrete base within 3 hours of placing
the concrete
 It will bond strongly to the concrete
 The screeds will also dry slowly with the concrete so that
drying shrinkage and cracking of the screed will be
minimized .
 For this monolithic construction of screed , a thickness of
12mm of screed will suffice

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Screeding
 Bonded screeds (on hardened concrete)
 A screed lain on a concrete base that has set and hardened
 It should be at least 40mm thick
 To provide a good bond between the screed and the
concrete, the surface of the concrete should be hacked by
mechanical means , cleaned and dampened and then covered
by a thin grout of water and cement or bonding agent
before the screed is laid

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Screeding
 Bonded screeds (on hardened concrete)

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Screeding
 Unbonded screeds
 A damp-proof layer is placed between the slab and screed

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Variations of Screeding
 Granolithic and Terrazzo finishes can be regarded as a
variation of the screeding by adding stone chippings into
the cement:sand paste.
 On granolithic finishes, crushed granite chippings are
added to the cement:sand paste.
 After laying, the topmost layer of the paste will be rubbed
off (by brush or high pressure water jet) to expose the
chippings.
 The resulting layer is superior in abrasion resistance and
extremely durable, and is ideal for external use

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 Terrazzo Finishes
 On Terrazzo finishes (also called
Shanghai Plastering), marble chippings
are used together with coloured
cement to provide a “classy” outlook.
 Normally, Terrazzo finishes are
smooth and polished (glossy surface)
 Apart from floor finishes, Terrazzo
can also by used as Wall Finishes
 Terrazzo can be made into the
terrazzo tiles instead of laying in-situ.
Terrazzo Tiles
Tile Finishes
 Tiles finishes are very popular for both wall and floor
decoration, as it offers virtually unlimited choices and
combinations (in term of colours, surface textures, sizes,
etc.). In addition, they are easy to be laid and fixed.
 Common materials tile include:
 Ceramics
 Stone
 Plastic (PVC)
 Timber (wood floorings)
 Clothing fibres (carpets)
 Others (rubber, etc.)

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Ceramic Tiles
 Ceramics are made from firing mixture of clay and other ingredients
at high temperature.
 As a result of this, ceramic tiles are durable and offer very good
resistance against chemical attack and can sustain high temperature.
 Apart from ceramic tiles, “Homogenous Tiles”, chemically similar to
ceramic tiles but are considered better in performances in many
areas than ceramic tiles are very popular in the market
 The surface treatment to ceramic tiles can be unglazed, glazed or
semi-glazed. The general properties of ceramics tiles are:
 Inorganic
 Nonmetallic
 Hard (but brittle)
 Electrical insulator
 Chemically stable
 Impermeable (glazed tiles)
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Anti-slippery Tiles
Fixing of Ceramic Tiles
 Cement/Sand Mortar is commonly used as the “adhesive” to
fixed ceramic tiles (wall and floor).
 To use mortar to fixed tiles, the tiles must be soaked in water
beforehand so that the tiles will not absorb water from the
mortar (which will affect the bonding between the mortar and
the background and also between water and the tiles)
 The gaps between tiles has to be filled by mortar or gap fillers
to ensure the tiled surfaces are impermeable
 Tile adhesives have been developed in the last two decades for
fixing ceramic tiles on plastered surfaces directly
 Matching between tiles and tile adhesives is necessary to
ensure optimal bonding / adhesion

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Stone Tiles
 Stones tiles are manufactured by cutting from natural
stones.
 Common stones tiles are granite and marble. Sometimes
lime stones are also used for making stone tiles
 Because of the shear weight, stone tiles fixed on walls are
achieved by means of anchor or cleat and bolting.
 For stone tiles as floor finishes, cement:sand paste or
sand base can be employed as the background for
receiving stone tiles. In addition, stone tiles at external
ground floor are usually laid with interlocking pattern to
minimize movement caused by traffic on top

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Timber Flooring (Tiles or Strips)
 very popular for domestic floor finishes as it offers a
sense of warmth and resilience.
 timber can also be used for decorating walls
 Both softwood (e.g., maple, beech) and hardwood (e.g.,
teak, oak) are commonly used
 Common patterns include square tile form, long-strip
form and zigzag form
 For flooring, timber are fixed on the surface by nailing
and/or via adhesive
 For walls, timber strips or panels are fixed by nailing

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Plastic Tiles, Carpet Tiles & Rubber Tiles
 Plastic tiles are usually PVC (polyvinyl chloride) floor tiles
which offer a sense of resilience.
 PVC tiles are inexpensive and offer good resistance against
abrasion and are ideal for indoor area like classrooms
 PVC flooring can be in roll form or in tile form
 PVC Tiles are usually in the form of 300x300mm, 500x500mm
and 600x600mm.
 Rubber tiles are primarily used for outdoor applications where
prevention against slipperiness is of major concern
 Compared to Ceramic and Stone tiles, plastic and rubber tiles
have a relatively shorter lifespan
 Carpets can either be in the form of roll and tiles. By using
different fabrics, different surface textures and performances
can be achieved.

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Carpet
 Characteristics: warmth, resilience, sound-absorbing and
classy/elegant
 Commonly used in library, concert hall, theatre for sound
absorbing reason
 Used in hotel for classy/elegancy
 Made of various type of materials – both natural (e.g.
wool, cotton) or synthetic (e.g. acrylic)
 Various colour and textures
 Washing and cleaning may
be a trouble once stained

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Paints
 Paints are thin layers applied onto the wall surfaces which
impart colour, provide a protective layer and increase durability
of the surface covered by it.
 The general use of using paints as surface finishes:
 To protect the underlying surface by exclusion from external
environment
 To provide a decorative yet easily maintained surface
 To provide light- and heat-reflecting properties
 To give special effects
 General composition of paint:
 Binder (spread the paint over the surface & binds the pigment)
 Pigment (provides the body, colour and durability of the paint)
 Thinner / Solvent (to control / adjust the viscosity of the paint in use)
 In recent years, advanced materials like carbon nanotubes are
added to paints to improve performance on hardness,
resistance to scratch, bacteria resistance and ease of cleaning
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Paints
 Types / Classification of Paints
 Oil-Based Paints – glossy outlook, more durable
 Water-Based Paints (e.g., emulsion paints)
 Polyurethane Paints (strong odour and higher VOC
emission); used in floor under special use e.g.
laboratory, garage – extra durable, chemical stable.
Also more common for metal and wood.
 Paints are usually applied to the receiving surfaces in
multi-coat.
 Before applying, the surface to receive paints should
be free from dirt, grease, dust and with adequate key
to provide bonding with the paint to be applied.
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Paints
 Paints are to be applied in multi-coats by brushes,
rolls and spraying and can provide a variety of surface
appearance (gloss, semi-gloss, matt, profiled, etc.)
 Generally it comprises:
 Prime Coat for protect the surface from attack
(e.g., corrosion) and prepare the surface for
subsequent painting
 Undercoat is to give opacity and build-up the base
for receiving the final finishing coat
 Finishing Coat is to give the required colour and
texture to the surface
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PU paint – wooden floor; concrete floor
in garage / factory / laboratory

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Summary
 External and internal uses
 Plastering and rendering
 Screeding: typical and varieties
 Tile and carpet
 Timber floor
 Paint

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