Plaster plasterboard compressed cement

Wall and ceiling linings

The terms ‘wall lining’ and ‘ceiling lining’ refer to the internal wall and ceiling covering of the building as opposed to ‘cladding’ which refers to the external wall covering or, sometimes, roof covering.  Additionally, in this section, wall and ceiling lining are defined as being distinct from finishes (such as ceramic tiles, wallpapers and paints) which are usually applied to the wall or ceiling lining.

The most common forms of wall lining used in Australia are gypsum plasterboard, fibrous cement, timber or composite lining boards or sheets, plastic coated wall sheeting and solid plaster.

Timber and composite lining boards and sheets are covered in Section 2.  Timber and plastic coated wall sheeting is mentioned in Section 9.  In this section, we will concentrate on the other alternatives.

Plaster

The term ‘plaster’ refers to a jointless and usually smooth lining applied to the base wall or ceiling structure.

Solid plaster was one of the first lining materials to be used in buildings.  The plaster which was made of lime and sand, often with hair included, was applied in situ to the masonry wall or, in the case of a timber stud wall or ceiling, to timber ‘laths’ which are thin battens fixed close together to provide a base.

Today, solid or in situ plaster is reserved for solid masonry walls; timber stud walls are lined with plasterboard.  However, in situ plastering is a wet and messy process and often internal masonry is left unplastered (face brickwork, for example).

Composition

Plaster comprises a binder, clean sand and fresh water, which sets to a comparatively hard, dense layer.  The properties of the final product depend largely on the type and quantity of the binder used.

The binders most commonly used in Australia are gypsum plaster, Portland cement and lime (either quicklime or hydrated lime-refer to Section 5) or organic binders.

Gypsum plaster

Calcium sulphate or gypsum plaster can be used for undercoats and finishing coats.  (Plaster of Paris is one type of gypsum plaster.) It is derived from naturally occurring gypsum rock which has been pulverised and heated to drive off most of the chemically combined water, resulting in a white, pink or grey powder.  When water is added to gypsum plaster it sets and hardens into a crystalline solid, giving off heat and expanding slightly in setting.

Two other similar binders are derived from gypsum plaster: ‘hard wall plasters’ which provide a harder finish and Keene’s cement, which is the hardest of the gypsum plaster mixes.

Portland cement

Portland cement is sometimes used as a binder in undercoats and finishing coats where an exceptionally hard surface is required. Drying which is too rapid increases the likelihood of cracking, and shrinkage must be substantially complete before a further coat is applied.

Limes

Plasters in which limes are the only binders are rarely used today as the final strength is very low.

Workability agents or plasticisers, based on non-hydraulic lime or organic materials, are used to improve the workability of the mix and distribute shrinkage stresses, thus reducing visible cracking.

Process

The process of applying solid plaster to a base structure is known as rendering.  Solid plasters are usually applied in two coats.  The undercoat is often referred to as the ‘scratch coat’ and the finishing coat as the ‘set coat’.
If the base is particularly smooth and the suction uniform, a single coat only may be required; alternatively, a particularly irregular base may require three coats.

In some applications the coats may not be of the same composition but it is important that each coat be well matured before another coat is applied, especially if cement is used.  A general principle to be followed is that each successive coat should be weaker than the preceding one.

The choice of a plastering system depends upon the base to which the plaster is to be applied, the performance of the required finish and the texture desired.

Cement-sand or cement-lime plasters are moisture-resistant plasters, while gypsum-based plasters should be used internally in dry situations only.

Mixes containing Portland cement make the hardest plasters, and have the greatest resistance to impact damage.  Keene’s plaster is the hardest of the gypsum plasters, while lime plaster is the softest. Table 1 and Table 2 indicate suitable plaster mixes for two and three-coat internal plasterwork.

Finishing coat	Undercoats (by volume)
Cement setting	1 cement 4 to 5 sand 1/10 lime
Cement: lime: sand Gypsum plasters	1 cement 5 to 7 sand 1/10 lime
Gypsum plasters	1 plaster 2 to 3 sand (or 1 : 3 to 1 : 4½ by weight)
	1 gypsum plaster: 1½ sand: 1/10 lime (or 1 : 2 by weight, plus lime 5% of weight of plaster)

Table 1: Mixes for undercoats for internal two-coat and three-coat work

 

 

 

Background or undercoat	Finishing coats (by volume)
Brick, block, or concrete	1 cement 4 sand 1/10 lime
Cement: sand	1 cement 1 lime 5 sand
Cement: lime: sand	1 cement 1 to 2 lime 6 to 9 sand
Concrete background Cement: lime: sand (undercoat) Gypsum plaster	1 lime ¼ to 4 gypsum plaster

Table 2: Mixes for finishing coats for internal work

 

Preparation

Porous bases, such as clay bricks and concrete blocks, which have a comparatively high suction rarely require much preparation other than raking of the joints and the removal of loose material.

Smooth, dense materials, such as concrete, have little suction and offer no mechanical key and are either hacked or else treated with a spatter-dish, sand-cement mix, often including a PVA adhesive, to provide a key.

Rough textured surfaces, such as rough concrete, provide a good mechanical key and require little preparation.

 

Fibrous plaster

Fibrous plaster is made of gypsum plaster reinforced with sisal hemp fibre.  Nowadays it has been replaced by plasterboard for sheeting applications but is still used for the more complicated decorative mouldings.

Fibrous plaster is dimensionally stable and easily decorated but is not satisfactory in moist conditions.

Gypsum plasterboard

Plasterboard is the most commonly used lining for timber-framed construction and brick veneer.  It comprises a core of gypsum plaster reinforced with two outside layers of kraft paper, one on each face.  Some are available with an aluminium foil on the back which improves thermal insulation performance.

Plasterboards are easily decorated and are reasonably tough and strong in normal grades but are not satisfactory in damp situations.  A water-resistant board is available which is designed to be used in areas where high humidity persists and in wet situations where they are protected with tiles or a similar impervious material.

Sizes

Sheets are available in a broad range of sizes.  Thicknesses commonly used in domestic applications are 10 mm for walls and 13 mm for ceilings.  However, a 10 mm thick board is now available for ceilings also.

Fixing

The boards are fixed to the studs or ceiling joists by gluing or nailing with special flat-headed nails.  Boards are available with either square or recessed edges, the latter being used where a flush surface is required.  For a flush joint, a strip of perforated reinforcing paper is embedded in bedding compound in the recess and the area is covered with a topping cement (refer to Figure 1).

Figure 1: Joint for plasterboard with recessed edges

General properties of plaster and plasterboards

Thermal insulation

Plaster linings are relatively thin and make a correspondingly small contribution to the thermal insulation of a building.

Fire resistance

Normal plasters are non-combustible, have no ‘spread of flame’ and do not produce smoke.  Special fire-rated plasterboards are available for applications which require a fire rating.
Often, the addition of a specified thickness of plaster or render on internal masonry walls is used to achieve a required fire rating according to the Building Code of Australia.

Sound absorption

Ordinary plasters have fairly low sound absorption values but special acoustic plasters and plasterboards are available.

Sound insulation

As plaster linings are relatively thin, they contribute significant sound insulation to lightweight components only.  However, plaster can improve sound insulation by sealing the surface to porous base structures.

Hardness

In housing, a fairly soft finish may be preferred but harder surfaces are often required in public buildings and the choice of system should take this into account.  Metal angles are used to protect vulnerable corners and provide a line for the plasterer to work to (refer to Figure 2).

Figure 2: Expanded metal reinforcement used at external plasterboard corners

Durability

Gypsum-based products are not usually waterproof and the durability of the finish depends largely on the composition of the plaster.

Texture

Smooth-trowelled surfaces comprising either neat gypsum or gypsum with admixtures are most common but texture can be provided by special trowelling or by including sand in the finish.  ‘Bagged’ finishes are popular on masonry walls.  These comprise a thin sand-cement mix which is wiped over the wall surface with a piece of heshian.  The resultant thin coat allows the form of the masonry units to show through.

 

 

 

Plasterboard

This guide provides detailed installation information for the fixing of Gyprock® plasterboards in residential construction including wet area applications.
For additional information or assistance with plasterboard fixing. please contact the CSR Gyprock office in your region.

 

Description
GYPROCK plasterboard is a machine made sheet composed of a gypsum core encased in a heavy duty linerboard. The linerboard is folded around the long edges to reinforce and protect the core. The board ends are cut square. GYPROCK plasterboard conforms with manufacturing standard AS/NZS2588 ‘Gypsum Plasterboard’.

Applications
GYPROCK plasterboard is used as an internal lining board to provide smooth, strong, long-lasting walls and ceilings for homes, offices, hospitals, hostels for the aged, schools, shops and factories. Its durable surface will accept most types of decorative finishing, including paint, wallpaper and texture compounds.
Joints between GYPROCK plasterboard sheets are reinforced and concealed to provide a smooth, durable finish to the whole surface. Alternatively, the joints may be covered with a decorative moulding.
Standard GYPROCK plasterboard or GYPROCK AQUACHEK can be used for exterior ceilings and eaves lining, provided the ceilings are protected from the weather.
GYPROCK FLAMECHEK MR plasterboard is fire and moisture resistant. When used in ‘wet areas’, installation is in accordance with the ‘Wet Area Installation’ section of this guide. When used in fire risk areas, installation is in accordance with the ‘General Installation’ section of this guide.

 

Advantages

Strength and Stability

GYPROCK plasterboard is a stable building product when subjected to the normal range of ambient temperatures and humidity.
Thermal coefficient of expansion is 16.2 x 10-6/°C in the temperature range 4°C to 38°C.
Hygrometric coefficient of expansion is: 7.2 x 10–6mm/mm/% R.H. (5%-90% R.H.).
Thermal Resistance ‘R’
10mm thickness = 0.062 m2k/w.
13mm thickness = 0.074 m2k/w.
16mm thickness = 0.08 6 m2k/w.

STANDARDS.
The entire range of Gyprock® plasterboards, as referenced in this technical literature, comply with following standards.

Plasterboard Manufacture.
AS/NZS2588 Gypsum Plasterboard. Plasterboard Installation.
AS/NZS2589 Gypsum linings in residential and light commercial construction – Application and Finishing.

Plasterboard In Wet Areas.
AS3740 Waterproofing of Wet Areas Within Residential Buildings.

 

 

CD TECHNOLOGY.
Controlled Density (CD) technology is a unique manufacturing process which manipulates the core structure of plasterboard. This creates greater strength, lighter weight and superior paper to core bonding, meaning easier handling, better cutting, and a better quality plasterboard. CD Technology is used in the manufacture of 10mm and 13mm Recessed Edge GYPROCK plasterboard, 10mm GYPROCK SUPACEIL, 10mm and 13mm Square Edge GYPROCK plasterboard, and most GYPROCK plasterboard ceiling panels.

 

 

ARCHITECTURAL SPECIFICATION

SCOPE

The contractor shall furnish all materials, labour and equipment required to satisfactorily complete the installation and jointing of all Gyprock® Plasterboard where indicated on the drawings and/or as specified.
DELIVERY & STORAGE OF MATERIALS.
All materials shall be delivered and stored in an enclosed shelter providing protection from damage and exposure to the elements. Damaged or deteriorated materials shall be removed from the premises.
MATERIALS.
All lining materials shall be GYPROCK plasterboards, adhesives, fasteners and jointing products as manufactured or supplied by CSR Gyprock.
Non-loadbearing metal wall components and ceiling components shall be those manufactured by Rondo Building Services Pty. Ltd (or products of equivalent or better performance).
FRAMING OR SUBSTRATE.
All framing shall be prepared to *Level……… Finish specifications as detailed in the Gyprock® Plasterboard Residential Installation Guide’, N°GYP547, and AS/NZS 2589.1 ‘Gypsum linings in residential and light commercial construction – Application and Finishing.’
Framing must also conform to structural standards specified by the appropriate building authorities and/or Australian Standard.

 

PLASTERBOARD INSTALLATION.

The framing shall be lined on the first side with *      layer(s) of    mm Gyprock®......... plasterboard.
The framing shall be lined on the second side with *   layer(s) of   mm Gyprock®......... plasterboard.
PLASTERBOARD FIXING AND JOINTING.

Gyprock® plasterboard shall be fixed, jointed and finished to a *Level   Finish as detailed in the Gyprock® Plasterboard Residential Installation Guide’, N°GYP547, and AS/NZS 2589.1 ‘Gypsum linings in residential and light commercial construction – Application and Finishing.’
* Insert or select appropriate specification.

 

Gyprock® Plasterboard Range.
TABLE 1. GYPROCK PLASTERBOARD AVAILABILITY.
Colour shading behind each product approximates the colour of the product face liner sheets

GYPROCK Product	Thickness mm	Width mm	Sheet Length (mm)								Mass kg/m2
			2400	2700	3000	3600	4200	4800	5400	6000
CD RECESSED EDGE	1 0	1200	W	W	W	W	W	W	W	W	6.5
		1350	W		W	W	W	W		W
	13	900		*üWSN	W	W					8.5
		1200	SN	ü	üü	ü	W	ü	SN	WSN
		1350			ü	üü	SN	W
CD SQUARE EDGE	1 0	1200	W	SN	WSN	W					6.5
	13	1200		SN	SN						8.5
SUPACEILTM	10	900	W		W	W		W			7.2
		1200	SN	W	ü	▲üA	ü	ü	üü	ü
		1350	W		ü	üü	ü	ü		ü
SOUNDCHEKTM	10	1350						ü			9.3
	13	1200			ü						13.0
AQUACHEKTM	10	1200	ü	SN	ü	üü	ü				8.0
		1350	SN	SN	WSN	SN		WSN
	13	1200		W	ü	W					10.4
IMPACTCHEKTM	13	1200			ü						10.3
BRACECHEKTM	10	1200				ü					8.4
FLEXIBLE	6.5	1200				ü					4.25
FLAMECHEK MRTM	10	1350						ü			8.0
FYRCHEKTM	13	1200		W	ü	ü					10.5
	16	1200	SN	W	ü	ü					12.5
FYRCHEKTM MR	13 16	1200 1200		WSN WSN	W	SN SN					10.7 13.5
PERFORATED SHEET	13	1200				ü					10.0
SHAFT LINER PANEL	25	600			ü						19.8
COVE CORNICE	–	55			ü	üü	ü	ü			0.68kg/m
	–	75			W	W	W	W			0 .93kg/m
	–	90			ü	üü	ü	ü	ü		1 .3kg/m
CLASSIC CORNICE	–	90						ü			1.2kg/m
TEMPO CORNICE	–	90						ü			1 .6kg/m
SYMPHONY CORNICE	–	75						ü			0.90kg/m
CONCERTO CORNICE	–	90						ü			1 .4kg/m

 

Indicates available in: ü = Australia wide; W = Western Aust.; S = South Aust.; N = Northern Territory. Indicates NOT available in: W = Western Aust.; S = South Aust.; N = Northern Territory.
* = Length is 2740. ▲ = 3300 and 3900mm lengths also available in WA only.
In Western Australia only, additional Recessed Edge/Square Edge products are available.

Gyprock® Plasterboard Range.

 

GYPROCK Plasterboard CD
Recessed Edge.
Features.

• 1 .5mm recess on face side allows formation of shallow channel for joint reinforcement.
• Provides smooth. even and continuous surface once jointed.
• 10mm and 13mm thickness.
• Manufactured to the requirements specified in AS2588 : 1998 – Gypsum Plasterboard.
• Manufactured with CD technology. Applications.
• Internal walls and ceilings.

 

 

 

GYPROCK Plasterboard CD

Square Edge.

Features

• Manufactured with CD technology. Square Edge Finishing.
• The square edge allows sheets to be butted together neatly.
• These joints may be covered with aluminium, vinyl or timber mouldings.

Bevelled Edge Finishing.

• Edges are slightly bevelled.
• Edges are butted together to form a neat V-joint.
• Joints do not need to be covered with battens or finished with compounds.
• Manufactured to the requirements specified in AS2588 : 1998 – Gypsum Plasterboard.

Applications.

• Internal walls.
• Usually commercial construction, especially for office partitioning.

 

 

Aquacheck

Features.

• Specially processed plasterboard.
• Both the core and linerboard facing are treated in manufacture to withstand the effects of moisture and high humidity.
• Manufactured to the requirements specified in American Society for Testing and Materials C630.
• For use as a wall and ceiling lining in ‘wet areas’ and high moisture areas in residential and commercial applications.
• Recessed edges allow flush jointing to Recessed Edge Plasterboard.

Applications.

• GYPROCK AQUACHEK is a suitable substrate for ceramic tiles.
• Usage areas include bathrooms, kitchens, laundries. garages and ceiling applications such as walkways and verandahs.
• The GYPROCK AQUACHEK Wet Area Lining System is suitable for Category 1 Wet Areas (ie. shower recesses and bath installations as defined in AS3740).

 

 

Soundcheck

Features.

• Designed to provide enhanced acoustic resistance in wall and ceiling systems.
• A machine made sheet composed of a high density gypsum core encased in a heavy duty linerboard.
• Long edges are recessed to assist in producing a smooth, even and continuous surface once jointed.
• 10mm and 13mm thickness.
• Manufactured to the requirements specified in AS2588 : 1998 – Gypsum Plasterboard.

 

 

 

Bracecheck
Features.

• A 10mm thickness high strength plasterboard designed for bracing applications.
• A machine made sheet composed of a high density gypsum core reinforced with cellulose and glass fibre, encased in a heavy duty green coloured linerboard.
• Long edges are recessed to assist in producing a smooth, even and continuous surface once jointed.

 

 

 

Flexible Plasterboard

Features.

• 6.5mm thickness plasterboard with an enhanced core to allow bending to small radii.
• Designed for installation as a two layer system.
• Long edges are recessed on the face side to assist in producing a smooth, even and continuous surface once jointed.
• Manufactured to the requirements specified in AS2588 – Gypsum Plasterboard.
• Manufactured with CD technology.

Applications.
Curved internal walls and ceilings

 

 

Impactcheck
Features.

• 10mm thickness plasterboard reinforced with a woven fibreglass mesh.
• High strength to resist soft body impact damage.
• Long edges are recessed on the face side to assist in producing a smooth, even and continuous surface once jointed.
• Violet coloured face linerboard for easy identification.

Applications.

• High traffic areas such as hallways, stairways, playrooms and garages.

 

Flamecheck
Features

• Fire and moisture resistant plasterboard.
• 10mm thickness with recessed edges for flush jointing.
• Blue coloured face linerboard for easy identification.
• For use as a wall and ceiling lining in ‘wet areas’ and areas of high fire risk.

Applications

• Usage areas include kitchens, bathrooms, laundries. garages.
• GYPROCK FLAMECHEK MR is suitable for Category 1 Wet Areas (ie. shower recesses and bath installations as defined in AS3740) and as a substrate for tiling.

 

 

 

 

Cornice

Features

• Cove Cornice in 55 and 90mm is available in all states. 75mm cove is available in W.A. and Victoria ONLY.
• Classic Cornice and Tempo Cornice are 90mm decorative profiles, and are available in all states.
• Gyprock® Cornices are supplied in a range of lengths from 3000mm to 5400m.

Applications.

• Provides an attractive finish to the junction of the walls and ceilings.
• Can be used on a variety of surfaces, including: GYPROCK Plasterboard,   plasterglass, cement render, masonry.
• A necessary part to some fire-rated ceilings.

 

Handling & Storage.

All materials must be kept dry, preferably by being stored inside the building. Care should be taken to avoid sagging or damage to edges, ends and surfaces.
All GYPROCK plasterboard should be stacked flat, properly supported on a level platform or on support members which extend the full width of the sheets and which are spaced at maximum 600mm centres.
If stored outside, sheets are to be stored off the ground, stacked as previously detailed and protected from the weather.

Design Considerations.

Levels of finish

Levels of finish are defined in the Australian/New Zealand Standard AS/NZS 2589.1 : 1997 ‘Gypsum linings in residential and light commercial construction – Application and Finishing.’ This standard is intended to provide builders, plasterboard installers and finishers, and their customers with the various defined methods and practices necessary to meet the customers expectations in terms of the ‘Level of Finish’.
Six ‘Levels of Finish’ (0, 1, 2, 3, 4 and 5) are defined, and minimum specifications to achieve each level of finish are detailed in the standard for each of the installation processes from framing preparation to finishing.
It is essential to determine the level of finish required before the frame construction begins as specific tolerances are required for frame alignment as well as plasterboard fixing and finishing for each of the levels of finish.
Unless these requirements are met throughout construction, it may not be possible to attain the desired finish level without extensive corrective measures.
The level of finish specified also affects the methods of jointing, particularly butt joints and back-blocking requirements, the number of coats of joint compound applied as well as the fitting and finishing of stopping and corner accessories.
It should be noted that, generally, domestic applications should be prepared to a minimum ‘Level 4 Finish’ unless specifically a higher or lower level of finish is agreed to by all contracting parties.

ROOF SPACE VENTILATION.

GYPROCK plasterboard will give many years of satisfactory performance under a wide range of climatic conditions, but to ensure long term performance to both lining material and paint finishes, the roof spaces should be adequately ventilated. A failure to do so may result in the plasterboard sagging, or the excessive moisture movement of the timber framing causing nail popping or joint deformation.
The aluminium foil sarking on roofs should be installed in accordance with the relevant Australian Standards for reflective foil laminates.
Condensation within a building is the result of a temperature difference from one side of a building element to the other. The temperature differential forces water vapour contained in the warmer air to flow towards the cooler region where it condenses on any surface below the ‘dew point’ temperature of the air.

 

Vapour barriers are incorporated into the structure to prevent the flow of water vapour from the warm to the cool regions. As a general rule, locate the vapour barrier as close as possible to the surface which will normally be at the higher temperature at the time of the condensation hazard.
Attics or similar unheated spaces above ceilings can be adequately ventilated as follows:

• Provide effective cross-ventilation for all spaces between roof and top floor ceilings by screened louvres or other approved and acceptable means.
• Ratio of total net free ventilating area to area of ceiling shall not be less than 1/150.

In rooms such as bathrooms, kitchens, and laundries, moisture laden air should be exhausted to the outside of the building, not in to the roof space.

Roof space ventilation
FIRE RESISTANCE.
All Gyprock® plasterboard is fire resistant to some degree. Gyprock FlamechekMRTM, however, has been formulated to have even greater performance than standard board. In comparison to 10mm Gyprock® plasterboard CD, FlamechekMRTM was found to be up to 50% better at resisting the effects of fire on walls and ceilings where there were no penetrations or openings. In any case, penetrations and openings can reduce the fire resistance of a system.
Smoke alarms save lives and CSR Gyprock recommends that suitable alarms be installed. Fire extinguishers and fire blankets should also be accessible.
Gyprock FlamechekMRTM cannot be used as a substitute for Fyrchek. Systems with Fire Resistance Levels incorporating Gyprock FyrchekTM plasterboard are presented in the Gyprock Fire & Acoustic Design Guide.

Control Joints
Movement and stresses created by temperature and humidity fluctuation, can result in deformation and damage to internal linings and partitions.
It is recommended that GYPROCK plasterboard surfaces be isolated from structural elements, except the floor, by the use of control joints or other means where:

• A GYPROCK plasterboard surface abuts any structural element or dissimilar wall or ceiling assembly
• The construction changes within the plane of the partition, wall or ceiling lining
• Control joints incorporated in a building to permit movement in the structure must be carried through all areas lined with GYPROCK plasterboard.
• Refer to page 25 for installation details.

 

LIGHTING.

Any imperfection in a completed lining installation will be made obvious by a condition called critical lighting or glancing light, where the incident light from an artificial or natural light source is nearly parallel to the surface. Glancing light also greatly exaggerates the size of imperfections making them glaringly obvious.
Ways to minimise the effect of critical lighting from artificial lighting sources are:

• Locate fluorescent lights about 450mm below the ceiling as this will give a more even distribution of light.
• Use more rather than fewer lights and install at regular spacings to give a more even, diffused light and to minimise the shadows that can occur from a single row or single light source.
• Recess light fittings into a ceiling (although recessed lights are more likely to be associated with glare problems).
• Allow a generous angle of incidence to the surface for feature lighting such as spotlights, to minimise the highlighting of imperfections.
• Do not locate a single or isolated unshaded light source close to a wall or ceiling in a space which has generally low levels of light.
• Do not use uplights, wall-washers and spotlights in areas with a smooth wall finish to eliminate light being emitted at a glancing angle to the surface.
• Design soft rather than harsh lighting conditions.

Ways to minimise natural lighting problems, particularly from direct sunlight, are:

• Do not take window glazing right up to the ceiling level.

 

• Avoid placing windows immediately adjacent to the end of a wall.
• Provide sun shades over the window.
• Recess the window to stop the sunlight reaching the wall.

HEATING.

The following situations may give rise to localised high temperature conditions (≥45°) which may be detrimental to wall and ceiling linings:

• Radiant ceiling heaters,
• Heat pumps,
• Reverse cycle air conditioners,
• Solid fuel stoves.

Refer to heating unit manufacturer for more information.

 

APPLIED FINISH SELECTION.

Finishes applied to the GYPROCK plasterboard can have a significant effect on the perceived quality of the installation, particularly where critical lighting conditions exist.
General rules when selecting the applied finish are:

• The difference in texture and absorption characteristic between the body of the sheet and the joint may show through some thin paint coatings.
• Imperfections show more readily on ceilings than on walls.
• Textured or heavy patterned finishes tend to hide imperfections.
• Matt finishes minimise imperfection visibility.
• Semi-gloss and gloss finishes highlight imperfections.
• Lighter colours (when compared to darker colours) are:

Less likely to show imperfections and impact damage.
More effective at diffusing the light and reducing shadow effects, particularly in smaller rooms.

• Gloss paints tend to highlight paint application variations (e.g. where a good wet edge has not been maintained when painting).
• Paint or thin wallpaper finishes are less tolerant of imperfections.
• Paint applied with a longer pile roller tends to mask imperfections better than those applied with a short pile roller.

Garage Ceilings

Ceilings in garages are subjected to different environmental conditions to those in habitable rooms. The following conditions may occur:

• Wind loads can disrupt uncured adhesive and prevent an effective adhesive bond from ever forming.
• Door operation may induce vibration in ceiling framing, adversely affecting nailed joints and disrupting adhesive bond.
• Framing that changes direction in the garage may result in insufficient perimeter support for the plasterboard.
• Moisture and high humidity in the garage can result in poor joint performance.

The above issues can also result in the poor performance of any installed cornice.

While the performance expectations for garage ceilings remain the same as for internal ceilings, additional details are required to ensure this performance is achieved.

• Use the 1/3 spacing method of fixing plasterboard, as detailed in this manual.
• Use screws not nails to fix ceilings.
• Use trimmers across the sheet width for support (refer to FIG 1).
• Back-block all joints in garage ceilings.
• Use a good quality wallboard sealer and two coats of paint.
• In areas of high humidity, use Gyprock® Wet Area Base Coat in the jointing system.

 

 

Fibrous cement

Fibrous cement sheeting has replaced asbestos cement as a lining and cladding material due to the health hazards associated with materials containing asbestos.

Composition

Fibrous cement is made from a mixture of Portland cement, sand, cellulose fibre and water, compressed into sheets, boards or other shapes.

Sizes

Sheets are available in a number of sizes.  Thicknesses for domestic use are generally as follows:

• as lining material for eaves, verandahs or carports – 4.5 mm or 6 mm sheet
• for internal wall and ceiling linings – 6 mm
• compressed fibrous cement for wet area floors – 15 mm or 18 mm thick.

Fixing

Sheets can be glued or fixed with special galvanised flat-head fibrous cement nails to timber frames.  Sheet ends can be covered with PVC end caps while joints can be covered with PVC sheet holders or fibre cement cover moulds (refer to Figure 3).

Figure 3: PVC end and Caps cover and Junction moulds

Exposed internal linings can be flush jointed.  Special recessed-edge sheets are taped with a perforated paper reinforcing tape and finished in a similar way to plasterboard sheets, with a topping cement.

Uses

Externally, fibrous cement products can be used as cladding in the form of boards, sheets or shingles.  However, internally, because they are waterproof, fibrous cement sheets are used primarily as a base lining for other finishes (such as tiles) in wet areas.  Compressed fibrous cement sheeting is also used as a base floor material for ceramic tile floors in wet areas.

General properties

Thermal insulation

Fibrous cement sheets are relatively thin and make a correspondingly small contribution to the thermal insulation of the building.

Fire resistance

Fibrous cement products will not burn, have a zero ‘spread of flame’ index and do not produce smoke.

Sound absorption

Unless special acoustic material is used, fibrous cement lining contributes little to the sound absorption characteristics of a room.

Sound insulation

The sheets have a greater density than plasterboard but are thinner and therefore do not significantly affect sound insulation.

Hardness

Care should be taken during handling and storage to prevent edges from chipping since the material is particularly brittle.  When painted or otherwise finished, however, a hard surface finish can be obtained.

Durability

Fibrous cement sheets are unaffected by sunlight, moisture or termites and should not split or rot.  Hence its suitability for external and wet area applications.

Thermal insulation

The question of thermal insulation really forms part of the problem of energy efficient design of the building as a whole, which includes consideration of the following points:

• orientation of the building to maximise the use of solar energy (refer to Figure 4)
• location in relation to summer breezes (refer to
• Figure 5)
• protection from winter winds (refer to
• Figure 6)
• location and treatment of windows (refer to Figure 7)
• use of wide eaves or pergolas which shade windows and walls from summer sun but allow entry of winter sun (refer to  Figure 8)
• use of solar energy in the design to heat floors or walls (refer to Figure 9)
• interior planning (refer to
• Figure 10)
• prevention of heat loss through unnecessary gaps (refer to
• Figure 11)
• design of floors (refer to
• Figure 12)
• the colour of the exterior of the house.

Figure 4: Paths of the sun in winter and summer

Figure 5: Location in relation to summer breezes

 

 

Figure 6: Protection from winter winds

Figure 7: Location and treatment of windows

Figure 8: The use of wide eaves or pergolas

Figure 9: The use of solar energy to heat floors or walls

Figure 10: Interior planning

 

Figure 11: Prevention of heat loss through unnecessary gaps

Figure 12: Prevention of heat loss through the floor by enclosing the sub-floor space

Thermal insulation can assist by improving the thermal efficiency of the structural components of the house by reducing heat loss or gain through the major surfaces, such as the walls and ceilings.

Heat transfer

Heat is transferred by:

• conduction-heat is ‘led’ from the side of the material at a higher temperature to the side at a lower temperature
• convection-when air is heated it expands and begins to circulate and heat up colder surfaces by losing some of its heat to them
• radiation-when air comes in contact with a warm object, heat is transferred to the atmosphere.

Thermal resistance

A material’s ability to resist the flow of heat is called its thermal resistance or ‘R-value’.  The higher the R-value of a material, the greater its ability to resist the flow of heat.

The Energy Authority of NSW provides data on recommended R-values for different areas in NSW.  For instance, if you live in Coffs Harbour the recommended minimum level of thermal insulation is R1.5 but if you live in Cooma, which is colder, the recommended minimum level is R3.0 (refer to
Figure 13).

 

Figure 13: Thermal insulation levels for NSW

The heat flow through a wall or ceiling is not reduced in direct proportion to the R-value of any insulation added above the recommended level.  In fact the extra benefit to be gained diminishes fairly rapidly beyond this level.

Thus, there is not much point in installing insulation to a value beyond the recommended R-value for your area.

Required R-values in New South Wales

Recent amendments to the BCA have included requirements for the inclusion of insulation in roofs, walls and under elevated floors.  The requirement depends on the location of the building.

New South Wales is divided into 4 zones and shown in

Figure 14 on the next page.  The R-values that need to be achieved under the deemed-to-comply provisions are given in Part 3.12 Energy Efficiency of Volume 2 of the BCA 2008.

 

Figure 14: Climate zones in Australia
(reproduced from BCA Zone Map)

Types of insulation

Reflective

This type of insulation uses the heat-reflective properties of aluminium foil which prevents heat transfer by radiation.  The following types are available:

• Foil laminated to reinforcing membranes, supplied in rolls of varying widths.  This is used for roof sarking and wall sheathing.
• Laminated foil layers separated by partition strips.  When the foil is installed over ceiling joists, the partition strips separate the two layers and provide an additional air space to increase the effectiveness by decreasing conduction.
• Foil laminated to bulk insulation.
• Foil-backed plasterboard.
• Solar reflective film which can be applied directly to glass panes.
• Metal reflective-treated fabrics for blinds, curtains and so on.

Bulk

This is normally a cellular material with entrapped air bubbles which slow down heat transfer by conduction.  Several forms are available.

Batts and blankets

Insulation batts and blankets are available in various materials as listed on the next page.

Insulation batts and blankets are available in:

• Mineral wool (fibreglass or rockwool) – manufactured from inorganic raw materials that are melted at above 1000°C and spun into fibres which are then bonded together to form flexible sheets.
• Urethane foam sheet – made from foamed polyurethane.
• Expanded polystyrene sheet (EPS) – made from foamed polystyrene.

Loose fill

Loose fill insulation is available in:

• Cellulose fibre – manufactured from waste paper.
• Exfoliated vermiculite – manufactured from a micaceous material.
• Mineral wool – manufactured as explained above.

In-situ foam

In-situ foam insulation is available in:

• Urea formaldehyde – pumped in as a mixture of chemicals using special equipment.  The mixture foams up in situ and forms a rigid foam filled area.
• Urethane foam – pumped as fluid foam into the space where it sets chemically to form a rigid insulation.
• Expanded polystyrene beads – mixed on site with a bonding agent and injected into the cavity.

Structural and decorative insulation

This type of insulation comprises a complete wall or ceiling lining system combining thermal insulation and often acoustic modification with a decorative lining.

Several forms are available:

• Fibreglass panels – laminated with decorative finishes.
• Wood wool panels – decorative boards made from wood straw bonded with a cement-like adhesive.
• Compressed straw panels – manufactured from pine or straw fibres which are compressed and bonded together.
• Expanded polystyrene – as above with decorative finishes.
•  

General properties of insulation materials

Thermal performance

The type and thickness of the insulation is selected according to the required R-value and the application. The R-value should be marked on the product and manufacturer’s product information should comply with SAA Standards and Test Methods.

Insulation products should be installed as specified by the manufacturer to be most effective.  For example, reflective foil used as insulation in horizontal applications should be laid face down as settling dust renders the upper face (usually coloured blue) ineffective.

Acoustics

Some insulation will also contribute to the acoustic performance of the room, especially in the case of some of the decorative panels.

Fire resistance

Some insulation materials are combustible. Combustible insulation should be covered with an appropriate non-combustible lining such as gypsum plasterboard.  Urethane foam, expanded polystyrene and cellulose fibre insulation must contain fire-retardant chemicals.

Safety

Most bulk insulation materials should be handled with care to avoid dust formation.

Gloves and long clothes should be worn when installing fibreglass to avoid contact with glass fibres, which may irritate the skin.  In all cases it is advisable to wear a mask covering the mouth and the nose.

Suitability

The type of construction will limit your choice of insulation system.

For instance,

• Loose-fill insulation is generally only suitable on flat surfaces.
• Loose-fill insulation is good for difficult corners.

In situ insulation may make access to the roof space extremely difficult.

 

Where to insulate

For the minimum requirements, refer to Part 3.12 Energy Efficiency of Volume 2 of the BCA 2008.

Because heat rises, most heat loss occurs through the ceiling. Figure 15 illustrates the proportion of heat loss through various paths for a typical uninsulated detached brick veneer dwelling in Canberra.

(Note that the figures given have been calculated specifically for the Canberra region and may not apply to other areas although the general pattern these figures reveal would apply for this type of construction elsewhere.)

Figure 15: Heat loss through a building

Although the percentage figure for heat loss through the walls is the highest, in terms of unit area the diagram suggests that (for this type of construction) the greatest heat losses are in fact through the ceiling and, next, the floor.  Consequently, the first place to consider insulating is above the ceiling (refer to Figure 16).

Figure 16: Insulation above the ceiling
If the floor is a raised timber floor the sub-floor space should be enclosed, allowing for the required ventilation, and bulk insulation can be supported between the joists or reflective foil can be placed over the joists (refer to Figure 17).

Figure 17: Insulation below the floor

In extremely cold climates rigid foam insulation around the edges of the slab is advantageous (refer to Figure 18).

Figure 18: Insulation around the edges of the slab

In timber walls bulk insulation can be placed between studs (refer to Figure 19).

Figure 19: Insulation between the studs

Foam in-situ insulation can significantly increase the thermal performance of cavity brick walls (refer to Figure 20).
Figure 20: Insulation between walls

The thermal performance of windows can be increased dramatically with double glazing or even triple glazing in extremely cold climates.  Another solution is to use full length drapes with pelmets will also greatly reduce heat loss.

Figure 21: Drapes and pelmets
Although materials can be introduced to improve the thermal performance of the building, total energy efficiency requires attention to the design of the building as a whole.  Some of the aspects which deserve attention, mainly those which can be easily attended to, have been touched upon in this section.