Section 6.5 – Timber joist

Timber joists ceilings and separating / compartment floors
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Timber joist
Ceilings to timber joist floors are an established form of
ceiling construction, which is widely used in both new
housing and refurbishment. Separating / compartment
floors are often specified as fire and sound resisting floors
in residential units such as flats and apartments to meet the
requirements of national Building Regulations.
Timber joist ceiling linings are quick and easy to install, and
provide a lining which can be jointed to give a seamless
finish ready for direct decoration or a traditional gypsum
plaster finish.
The ceilings comprise one or two layers of Gyproc
plasterboard screw-fixed or nailed to traditional timber joist
supports. Isover glass mineral wool insulation can be
included in the floor cavity to improve acoustic performance.
Key facts
1
●
Traditional and established method
●
Versatile
●
Use of Gyproc Drywall Timber Screws
minimises fixing defects
●
Gypframe RB1 Resilient Bar to provide
enhanced acoustic performance and
eliminate nail-popping
●
Can achieve high performance levels
●
Quick and easy to install
2
1
Gyproc plasterboard - direct fix with Gyproc Drywall
Timber Screw
2
Gypframe RB1 Resilient Bar - indirect fix
306
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✔
✔
Resid
e
High ntial Rise
Resid
e
Apar ntial tmen
ts
Resid
e
Hous ntial ing
Enter
tainm
ent
Custo
dial
✔
Audit
oria
✔
Indus
trial
✔
Healt
hcare
✔
Educ
ation
Retail
✔
Sport
& Leis
ure
Comm
ercial
6.5
Offic
es
Sector Guide
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COMPONENTS
Gyproc board products
Fixing and finishing products
Gyproc WallBoard 1, 2
Thickness
Width
12.5, 15mm
900, 1200mm
Gyproc Drywall Timber Screws or Glasroc
FireCase Screws
For a positive direct fix of boards to
timber joists.
Gyproc FireLine 1
Thickness
Width
12.5, 15mm
1200mm
Gyproc Drywall Screws
For fixing ceiling lining boards to Gypframe
SureFix Bars or Resilient Bars.
Gyproc SoundBloc 1
Thickness
Width
12.5, 15mm
1200mm
Gyproc Sealant
Sealing air paths for optimum sound
insulation.
Gyproc Plank
Thickness
Width
19mm
600mm
Gyproc jointing materials
For seamless jointing.
Gyproc 4x2’s
Thickness
Width
9.5, 12.5mm
600mm
Gyproc Skimcoat, Gyproc Carlite Finish or
Gyproc Board Finish
To provide a plaster skim finish.
Glasroc F MultiBoard
Thickness
Width
6, 10, 12.5mm
1200mm
Isover Acoustic Roll
For enhanced acoustic performance.
Glasroc F FireCase
Thickness
Width
15mm
1200mm
Timber joists ceilings and separating / compartment floors
T 00353 1 629 8400
Isover Modular Roll
For providing acoustic / thermal insulation.
Isover Sound Deadening Floor Slab
Moisture resistant boards are specifed in intermittent wet use
areas e.g. shower areas, bathrooms and kitchens.
1
Also available in DUPLEX grades where vapour control is required.
pour check is required.
2
Stone mineral wool
For providing enhanced fire performance in
some applications.
Gypframe metal products
Gypframe RB1 Resilient Bar
Prime dimension
16mm
Health and Safety
Safety Data Sheets for all Gypsum Industries’ products are
available to download from our website: www.gypsum.ie,
or via the Technical Sales Department.
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6.5
308
INSTALLATION
Direct fix plasterboard ceiling
Boards are fixed to ceilings, prior to lining walls and
partitions, with the long edges at right angles to the joists.
Cut-ends are located over a joist or timber nogging
support. Timber noggings (where required) are fitted
between joists at room perimeters to support board edges.
Noggings may also be required to support board edges in
the field of the boards. Boards are preferably fixed to
timber supports using Gyproc Drywall Timber Screws, to
minimise fixing defects.
Direct fix plasterboard ceiling
Boards are fixed to ceilings, prior to lining walls and
partitions, with the long edges at right angles to the joists.
Cut-ends are located over a joist or timber nogging
support. Timber noggings (where required) are fitted
between joists at room perimeters to support board edges.
Noggings may also be required to support board edges in
the field of the boards. Boards are preferably fixed to
timber supports using Gyproc Drywall Timber Screws, to
minimise fixing defects.
Indirect fix to Gypframe RB1 Resilient Bars
The bars are fixed through the single fixing flange to the
underside of timber joists (at 90° to them) using Gyproc
Drywall Screws. The first and last rows of Gypframe RB1
Resilient Bars are located at all wall perimeters. Boards are
fixed to the underside of Gypframe Resilient Bars with long
board edges at right angles to the bars. When fixing
boards, care must be taken to ensure that the plasterboard
fixing screws do not make contact with the joists.
Indirect fix to Gypframe RB1 Resilient Bars
The bars are fixed through the single fixing flange to the
underside of timber joists (at 90° to them) using Gyproc
Drywall Screws. The first and last rows of Gypframe RB1
Resilient Bars are located at all wall perimeters. Boards are
fixed to the underside of Gypframe Resilient Bars with long
board edges at right angles to the bars. When fixing
boards, care must be taken to ensure that the plasterboard
fixing screws do not make contact with the joists.
For full installation details, refer to the Installation Guide at www.gypsum.ie
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PERFORMANCE
Please refer to section 6.1 Introduction - for general considerations.
Table 2 - Dimensions and performance1 - Gyproc plasterboard linings
1
2
3
Gypframe RB1 Resilient
Bars at 450mm centres to
underside of joists.
100mm Isover Modular
Roll in the cavity.
Timber joists with suitable timber room perimeter
noggings. Noggings also required to support
board edges, unless otherwise stated.
Detail
Board type
Flooring Joist
board
centres
type2
Joist
width
(min.)
Fire
resistance6
mm
mm
mins
Estimated laboratory
Performance
sound insulation3 substantiation
100 - 3150Hz
report
Airborne
Impact
Lnw dB
Rw dB
1
One layer of 12.5mm Gyproc WallBoard
d
450
38
305
36
81
C014003
1
One layer of 12.5mm Gyproc WallBoard
a
600
38
30 (modified)4
38
79
C016001
1
One layer of 12.5mm Gyproc WallBoard
d
600
38
30
38
79
C016002
40
-
C106029
1
One layer of 15mm Gyproc WallBoard
c
600
38
305
2
Two layers of 15mm Gyproc WallBoard
d
600
47
60
40
76
C016006
2
Inner layer of 12.5mm Gyproc WallBoard
c
and an outer layer of 15mm Gyproc FireLine
600
38
60
40
76
C016008
2
Two layers of 12.5mm Gyproc FireLine
d
600
38
60
40
76
C016009
2
Inner layer of Gyproc Plank and an outer
layer of 12.5mm Gyproc WallBoard
b
600
50
60
40
75
C016007
3
Inner layer of Gyproc Plank and an outer
layer of 12.5mm Gyproc WallBoard
d
600
45
60
50
68
C206003
3
Inner layer of Gyproc Plank and an outer
layer of 12.5mm Gyproc SoundBloc
d
600
45
60
54
67
C016030
2
Two layers of 15mm Gyproc FireLine
d
450
47
90
40
78
C014011
1 The fire resistance and sound insulation performances are for ceilings incorporating tapered edge boards with all joints taped and filled
according to Gypsum Industries’ recommendations. The quoted performances are achieved only if Gypsum Industries’ components are
used throughout, and the Company’s fixing recommendations are strictly observed. Any variations in the specification should be checked
with Gypsum Industries. Where boards are fixed direct to timber joists, screw-fixing is the preferred alternative to nail-fixing and
minimises the risk of fixing defects occuring.
2 Floor types:
a Any structurally suitable wood board flooring.
b Wood board t & g flooring, not less than 15mm (finished) thickness.
c
Wood board t & g flooring, not less than 18mm (finished) thickness.
d Wood board t & g flooring, not less than 21mm (finished) thickness.
3 The acoustic ratings quoted above are based on 200mm deep joists and a walking surface of min. 9.6kg/m3.
4 30 : 15 : 15. If the floor type d is used the fire resistance increases to a full 30 minutes.
5 Noggings to support board edges not required.
6 Board joints must be reinforced with Gyproc Paper Joint Tape for the quoted fire resistance periods to be achieved. Please refer to
section 2.2 for full details.
Timber joists ceilings and separating / compartment floors
T 00353 1 629 8400
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Table 3 - Dimensions and performance1 - non-combustible board linings
1
2
3
4
5
6
Timber joists with suitable timber room perimeter noggings.
Noggings also required to support board edges, unless stated otherwise.
Detail
Board type
Flooring
board
type2
Joist
centres
Insulation
mm
Joist
width
(min.)
mm
Fire
resistance5
Performance
substantiation
report
mins
1
One layer of 6mm MultiBoard
b
450
38
-
30
G104019
1
One layer of 12.5mm MultiBoard
a
600
38
-
30
G106021
2
Two layers of 10mm MultiBoard
a
600
47
-
60
G106022
3
Two layers of 10mm MultiBoard
a
600
47
100mm Isover
Modular Roll
60
G106023
4
80mm x 10mm MultiBoard strips
(screw-fixed), with one layer of 10mm
Glasroc MultiBoard (screw-fixed)
b
4004
50
30mm stone mineral
wool (64kg/m3)
60
G104024
4
80mm x 10mm MultiBoard strips
(screw-fixed), with one layer of 10mm
MultiBoard (screw-fixed)
c
600
50
60mm stone mineral
wool (23kg/m3)
60
G106046
1
One layer of 15mm FireCase
(screw-fixed)3
b
600
38
-
60
G106025
4
100mm x 10mm MultiBoard strips
(screw-fixed), with one layer of 12.5mm
MultiBoard (screw-fixed)
d
6004
38
25mm stone mineral
wool (48kg/m3)
60
G106026
5
One layer of 12.5mm MultiBoard,
100 x 10mm MultiBoard strips and
an outer layer of 12.5mm MultiBoard
d
6004
38
-
90
G106027
6
One layer of 12.5mm MultiBoard,
100 x 10mm MultiBoard strips and
an outer layer of 12.5mm MultiBoard
d
6004
38
100mm Isover
Modular Roll
90
G106028
S
1 The fire resistance performances are for imperforate ceilings with all joints taped and filled in accordance with Gypsum Industries’
recommendations. The quoted performances are achieved only if Gypsum Industries’ components are used throughout, and the Company’s
fixing recommendations are strictly observed. Any variations in the specifications should be checked with Gypsum Industries. Where boards
are fixed direct to timber joists, screw-fixing is the preferred alternative to nail-fixing and minimising the risks of fixing defects occurring.
2 Floor types:
a 21mm plain edge wood board flooring.
b Wood board t & g flooring, not less than 18mm (finished) thickness.
c
Wood board t & g flooring, not less than 19mm (finished) thickness.
d Wood board t & g flooring, not less than 20mm (finished) thickness, or 20mm plain edge boarding with 3mm
hardboard or plywood.
3 Use 58mm FireCase Screws at 150mm centres. 38mm x 38mm timber noggings are also required between joists and at the perimeter to
support board edges.
4 Noggings to support board edges not required.
5 Board joints must be reinforced with Gyproc Paper Joint Tape for the quoted fire resistance periods to be achieved. Please refer to
section 2.2 for full details.
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Table 4 - Dimensions and performance1 - upgrading existing lath and plaster ceilings
1
2
Existing lath and plaster
ceiling supported by
chicken wire securely
nailed to the joists,
battened with 38mm x
38mm timber (at 600mm
centres with noggings or
450mm centres without
noggings).
Detail
3
Existing ceiling
underdrawn with
metal lath2 securely
fixed to the joists.
Board type
4
Existing ceiling
removed and metal
lath2 securely fixed to
the joists.
Existing lath and plaster
ceiling (up to 20mm
thick) supported by
chicken wire securely
nailed to the joists.
Flooring
board
type3
Joist
centres
Fire
resistance7
mm
Joist
width
(min.)
mm
Performance
substantiation
report
mins
1
One layer of 12.5mm Gyproc WallBoard
d
600
38
30
C016019
1
Two layers of 12.5mm Gyproc FireLine
b
600
38
60
C016022
2
13mm Gyproc Bonding or with 2mm
Gyproc Skimcoat or Carlite Finish
b
600
37
60
C016024
1
Two layers of 10mm MultiBoard
b
600
37
60
G106045
3
100mm x 10mm MultiBoard
with one layer of 12.5mm MultiBoard
a
600
50
60
G106029
4
19mm Gyproc Bonding or with 2mm
Gyproc Skimcoat or Carlite Finish
c
600
48
120
C016045
Timber joists ceilings and separating / compartment floors
T 00353 1 629 8400
1 The fire resistance performances are for imperforate ceilings incorporating boards with all joints taped and filled according to Gypsum
Industries’ recommendations. The quoted performances are achieved only if Gypsum Industries’ components are used throughout, and the
Company’s fixing recommendations are strictly observed. Any variations in the specifications should be checked with Gypsum Industries.
Where boards are fixed direct to timber joists, screw-fixing is the preferred alternative to nail-fixing and minimises the risk of fixing
defects occurring.
2 Where plaster is applied to ribbed metal lath, the plaster thickness is measured from the face of the lath, and the lath should be installed
in accordance with the manufacturer’s recommendations. With 120 minutes fire resistance construction, the metal lath is independently
fixed with wire supports from the joist sides.
3 Floor types:
a Wood board t & g flooring, not less than 20mm (finished) thickness, or 20mm plain edge boarding with 3mm
hardboard or plywood.
b Wood board t & g flooring, not less than 21mm (finished) thickness, or 20mm plain edge boarding with 3mm
hardboard or plywood.
c
Wood board t & g flooring, not less than 22mm (finished) thickness, or 20mm plain edge boarding with 3mm
hardboard or plywood.
d Any structurally suitable wood board flooring.
4 Assumes no contribution from the existing lath and plaster ceiling.
5 Bridging comprises of a layer of 12.5mm Gyproc MultiBoard resting on 100mm x 12.5mm Gyproc MultiBoard strips which are screw-fixed
to the sides of each joist flush with the bottom edge, strips fixed at 300mm centres, top and bottom.
6 Fix MultiBoard strips at 300mm centres, top and bottom.
7 Board joints must be reinforced with Gyproc Paper Joint Tape for the quoted fire resistance periods to be achieved. Please refer to
section 2.2 for full details.
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Table 5 - Dimensions and performance1 - compartment / separating2 floors
1
2
3
Platform floor.
Platform floor. 100mm Isover Modular
Roll between the joists. Floor type c3
CasoLine
MF4
GypFloor
hung underneath timber
with Gyproc Plank
joists to give a 277mm cavity, with
100mm Isover Modular Roll in the
80mm Isover Modular Roll
cavity. Gypframe RB1 Resilient bars
between the joists. Floor type c3
at 450mm centres.
4
5
GypFloor
SILENT
Separating sub-joist floor
with Gyproc Plank on
Gypframe SIF Floor Channels.
comprising of a platform floor.
100mm Isover Modular Roll in the
100mm Isover Modular Roll in the cavity.
Floor type c3
cavity. GypLyner framework to joists.
Detail
SILENT
on Gypframe SIF Floor Channels.
Board type
Flooring Joist
board
centres
type2
Joist
width
(min.)
Fire
resistance5
mm
mm
mins
Estimated laboratory
Performance
sound insulation
substantiation
100 - 3150Hz
report
Airborne
Impact
Lnw dB
Rw dB
1
One layer of Gyproc Plank with an outer
layer of 12.5mm Gyproc SoundBloc
c
600
44
60
62
56
C016038
2
Two layers of 15mm Gyproc SoundBloc
c
600
44
60
66
50
C106011
3
Two layers of 15mm Gyproc SoundBloc
b
450
45
60
61
56
C204006
3
One layer of Gyproc Plank and one layer
of 12.5mm Gyproc SoundBloc
b
450
45
60
63
55
C204001
4
One layer of Gyproc Plank and one layer
of 12.5mm Gyproc SoundBloc
b
450
45
60
63
55
C154008
5
Two layers of 15mm Gyproc SoundBloc
c
600
47
60
664
48
C106050
3
Two layers of 15mm Gyproc FireLine
b
450
45
90
60
57
C204002
1 The fire resistance and sound insulation performances are for ceilings incorporating tapered edge boards with all joints taped and filled
according to Gypsum Industries’ recommendations. The quoted performances are achieved only if Gypsum Industries’ components are
used throughout, and the Company’s fixing recommendations are strictly observed. Any variations in the specification should be checked
with Gypsum Industries’. Where boards are fixed direct to timber joists, screw-fixing is the preferred alternative to nail-fixing and
minimises the risk of fixing defects occuring.
2 If in doubt as to whether a floor is to be a compartment or separating floor, or both, please refer to the relevant Technical Guidance Document.
3 Floor types:
a Any structurally suitable wood board flooring.
b Softwood floor boarding, not less than 21mm (finished) thickness.
c
Walking surface of 18mm t & g wood board flooring, spot-bonded with Gyproc Sealant at 300mm centres to
a substrate of Gyproc Plank laid on 25mm Isover Sound Deadening Floor Slabs (64kg/m3) laid on a minimum
of 12mm wood based sheet sub-deck nailed to the joists.
4 Normal fixing centres for Gypframe MF5 Ceiling sections (450mm) and Gypframe MF7 Primary Support Channels (1200mm).
5 Board joints must be reinforced with Gyproc Paper Joint Tape for the quoted fire resistance periods to be achieved. Please refer to
section 2.2 for full details.
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Table 6 - Dimensions and performance1 - upgrading sound insulation of a basic floor
Existing basic floor
Upgrading
1
2
CasoLine
195mm x 45mm timber joists at
Detail
3
MF
hung underneath the basic
CasoLine
MF
hung from the basic floor
600mm centres with 18mm t&g
floor (ceiling removed) to give a
wood chipboard flooring.
277mm cavity. 80mm Isover Modular
give a 277mm cavity. 80mm
Roll in the cavity.
Isover Modular Roll in the cavity.
Board type
Approximate
weight
Floor
depth
kg/m2
mm
using Gypframe Acoustic Hangers to
Laboratory sound insulation
100 - 3150Hz
Airborne
Impact
Rw dB
Performance
substantiation
report
Lnw dB
1
Existing layer of 12.5mm Gyproc plasterboard
10
226
38
79
C106028
2
Two layers of 12.5mm Gyproc SoundBloc
23
320
60
60
C106007
3
Two layers of 12.5mm Gyproc SoundBloc
23
320
63
54
C106013
1 The sound insulation performances are for imperforate ceilings with all joints taped and filled according to Gypsum Industries’
recommendations. The quoted performances are achieved only if Gypsum Industries’ components are used throughout, and the
Company’s fixing recommendations are strictly observed. Any variations in the specifications should be checked with Gypsum Industries.
Table 7 - Dimensions and performance2 – ceilings below roof spaces
1
2
3
4
Timber joists or bottom chord of trusses with timber noggings between joists to support board edges and at room perimeter.3
Insulation laid between joists.
Detail
Board type
Max. joist/
truss centres
CasoLine
MF
Timber joists ceilings and separating / compartment floors
T 00353 1 629 8400
hung from joists.
Insulation laid over ceiling grid.
Insulation
type
mm
Min. joist /
truss
width
mm
Fire
Performance
resistance5 substantiation
report
mins
1
One layer of 12.5mm MultiBoard
600
38
150mm Isover
Modular Roll
30
G106041
2
Two layers of 12.5mm Gyproc WallBoard
600
38
150mm Isover
Modular Roll
30
C106049
1
One layer of 12.5mm Gyproc FireLine
600
38
150mm Isover
Modular Roll
30
C106047
4
Two layers of 12.5mm Gyproc WallBoard
600
354
100mm Isover
Modular Roll
30
C106045
2
Two layers of 10mm Gyproc MultiBoard
600
354
150mm Isover
Modular Roll
60
G106042
3
Two layers of 12.5mm Gyproc FireLine
600
38
150mm stone mineral
Wool (24kg/m3)
60
C106048
4
Two layers of 15mm Gyproc FireLine
600
354
30mm stone mineral
Wool (45kg/m3)
60
C106051
2 The fire resistance performances are for imperforate ceilings incorporating boards with all joints taped and filled according to British
Gypsum’s recommendations. The quoted performances are achieved only if Gypsum Industries components are used throughout, and the
Company’s fixing recommendations are strictly adhered to. Any variations in the specifications should be checked with British Gypsum. Where
boards are fixed direct to timber joists, screw-fixing is the preferred alternative to nail-fixing and minimises the risk of fixing defects occuring.
3 For fire-rated ceilings below roof spaces, noggings are required regardless of joist spacings and plasterboard thickness.
4 Nominal 50mm x 25mm timber battens should be fixed to the side of timber supports where the ceiling boards butt in order to maintain an
adequate bearing surface.
5 Board joints must be reinforced with Gyproc Paper Joint Tape for the quoted fire resistance periods to be achieved. Please refer to
section 2.2 for full details.
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Environmental
Gyproc plasterboard ceilings are unsuitable for use in areas
subject to continuously damp or humid conditions.
Plasterboards are not suitable for use in temperatures
above 49ºC but can be subjected to freezing conditions
without risk of damage.
Fire protection
For reaction to fire classifications for Gyproc and Glasroc
boards please refer to Section 2.1 .
Fire resistance
The fire resistances given in Tables 2, 3, 4, 5, 6 and 8 are for
imperforate ceilings tested to BS 476: Part 8: 1972 or
BS 476: Part 21: 1987, or BS 476: Part 22: 1987, or
assessments based on these tests.
Sound insulation
The airborne and impact sound ratings given in Tables
2, 6 and 7 are for imperforate ceilings and have been
tested in accordance with BS EN ISO 140-3: 1995 and
BS EN ISO 140-6: 1998, and rated in accordance with
BS EN ISO 717-1: 1997 and BS EN ISO 717-2: 1997.
Airtightness is essential for optimum sound insulation.
While most junctions will be sealed with standard jointing
materials, gaps at the perimeter of the floor and ceiling,
and other small airpaths, can be sealed using Gyproc
Sealant.
The sound insulation data quoted was measured in the
absence of flanking transmission. The performance of the
floor in practice will generally be governed by flanking
transmission.
Water vapour control
Where there is a requirement for a vapour control layer,
DUPLEX grade boards should be specified as the face layer
(i.e. the second layer in double layer linings). The
application of two coats of Gyproc Drywall Sealer to the
face lining will also provide a degree of vapour control.
Please refer also to Timber noggings overleaf.
Thermal properties
Isover insulation is laid between the joists where required
to provide the specified standard of thermal insulation.
6.5
314
DESIGN
Please refer to section 6.1
considerations.
Introduction - for general
Planning - key factors
To minimise the risk of ceiling finish defects occurring,
seasoned timber with a moisture content not exceeding
that recommended in BS 5268: Part 2: 2002 should be used.
The contractor should ensure that timber supports are
accurately spaced, aligned, and levelled. Consideration
should be given to using Gyproc Drywall Timber Screws as
the preferred method of fixing.
Cavity barriers
Cavity barriers may be required to satisfy the requirements
of national Building Regulations. Please refer to section
6.7 - Cavity barriers.
Strength and robustness
Timber should be aligned and level, and should meet the
requirements of BS 5268: Part 2: 2002. The dimensions and
assembly of timber supports should be sufficient to allow
positive fixing of boards without bounce or undue
deflection due to nailing, screwing, or other applied force.
When the minimum joist width conditions cannot be met, a
timber batten should be securely fixed to the side of those
timber supports where ceiling boards butt in order to
increase the bearing surface. Please refer to Joist width
overleaf.
Where plasterboards are fixed at maximum centres in
adverse conditions the standard of lining can be affected.
Adverse conditions can generally be described as conditions
where high humidity occurs, principally in the cold, damp,
autumn / winter period. They also refer to buildings under
construction during this period where both the structure
and wet applications such as plastering and screeding are
subject to slow drying conditions.
Where a polyethylene vapour control layer is included in
the ceiling construction in conditions described previously,
condensation can form on the polyethylene surface. This
can result in plasterboard becoming unduly damp, and
affecting the standard of acceptability of the lining and
any applied plaster or textured coating.
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Imposed loads
The designer should ensure that the floor construction is
suitable to support any imposed loads.
Timber noggings
Suitable timber noggings, normally 38mm x 38mm, may be
required between joists and at the room perimeter to
support board edges and board ends. The provision of
noggings depends on the thickness of boards used, and the
spacing of timber joists (please see Table 8). In addition, the
need for noggings is also dependent on any fire resistance
requirements, so Tables 2 and 7 must be referred to.
Timber noggings should always be provided at the room
perimeter except when using 15mm board or 19mm Gyproc
Plank in non-fire rated situations. When fixing DUPLEX grade
boards providing vapour control noggings are required
regardless of joist spacing or board thickness in order to
ensure that vapour control integrity is maintained.
In multi-layer plasterboard ceilings, the provision of
noggings relates to the outer layer board only, unless
otherwise stated.
Table 8 - Provision of timber noggings*
Board
thickness
mm
Maximum joist centres
with noggings
without noggings
mm
mm
6 MultiBoard
450
400
9.5 & 10
450
400
12.5
600
450
15 & 19
600
600
*Tables 2 to 7 must also be referred to for fire resistant ceilings.
Nail popping
Loosening of nails in timber can occur through timber
shrinkage (please see Fig 7), or as a result of fixing boards
to misaligned or twisted framing. To reduce the risks,
boards should be fixed tight to framing members.
To minimise any risk of fixing defects occurring use Gyproc
Drywall Timber Screws. If nails are the preferred fixing
method, the risk of subsequent fixing defects can occur.
Fixing to super-dried timber and engineered ‘I’ beams
It has been established by test that Gyproc Drywall Timber
Screws are the best solution for fixing to standard softwood,
super-dried timber (approximately 12% moisture content).
If engineered I joists are to be used, please contact the joist
manufacturer for fire resistance and sound insulation claims
and for fixing recommendations.
Services
Electrical and other small service runs can be routed within
the floor cavity. Services should be installed in accordance
with standards, guidelines and recommendations.
Fixtures / fittings
Fixtures should be made into joists, or to supplementary
timber.
Timber joists ceilings and separating / compartment floors
T 00353 1 629 8400
Finishing
Please refer to section 1.5 - Finishing Coat Plasters,
section 2.2 - Jointing, and section 2.5 - Decorative
Effects.
Estimating
The estimated construction time is 15 - 20m2 / hour (single
layer ceiling - boarding only) or 8 - 10m2 / hour (double
layer ceiling - boarding only) ready for finishing.
Joist width
Where joist width is less than the minimum stated in
Tables 2 - 7, the system may not meet its specified
performance.
If the minimum fixing tolerances cannot be met, 50mm x
25mm timber battens should be screw-fixed to the side of
the joists where ceiling boards abut in order to extend the
bearing surface.
Fixing to timber frames
A technical information sheet is available to download
from our website: www.gypsum.ie
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Timber joists ceilings and separating / compartment floors
www.gyproc.ie
CONSTRUCTION DETAILS
Fig 1 - Joists at 450mm centres using 12.5mm Gyproc WallBoard - board edge noggings not required unless stated in
performance tables*
1800mm
450mm
900
mm
Room perimeter noggings required.
* Note: where Duplex grade boards are specified to provide vapour control, noggings are always required regardless of joist spacing
and plasterboard thickness.
Fig 2 - Joists at 600mm centres using 12.5mm Gyproc WallBoard - board edge noggings required unless stated in
performance tables*
2400mm
600mm
1200
mm
6.5
Room perimeter noggings required.
* Note: where Duplex grade boards are specified to provide vapour control, noggings are always required regardless of joist spacing
and plasterboard thickness.
316
book 6_jan10a:c01 Introduction v3.qxd 15/04/2010 19:46 Page 317
F 00353 1 623 7054
E [email protected]
Fig 3 - Joists at 600mm centres using 15mm Gyproc WallBoard - board edge noggings not required unless stated in the
performance tables. Room perimeter noggings not required in non-fire rated situations*.
2400mm
600mm
1200
mm
Timber joists ceilings and separating / compartment floors
T 00353 1 629 8400
* Note: where Duplex grade boards are specified to provide vapour control, noggings are required regardless of joist spacing and
plasterboard thickness.
Fig 4 - Twisting of standard soft wood timber joist on drying from 20% to 8% moisture content
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Timber joists ceilings and separating / compartment floors
www.gyproc.ie
Fig 5 - Fixing boards to trussed rafters
35mm
25mm
Fig 6 - Fixing tolerances1
A
6mm
minimum
1 Boards should be lightly butted with a maximum separation of
3mm. Where a cut edge occurs, dimension ‘A’ is 13mm minimum,.
Where a bound edge occurs, dimension ‘A’ would be 10mm
minimum.
6.5
318
Table 9 - Fixing plasterboard to timber supports
Board
thickness
mm
Gyproc Drywall Timber
Screws to fix board for
direct decoration or
plastering
mm
Gyproc Nails to fix
plasterboard for direct
decoration or
plastering
mm
9.5
12.5
15
19
12.5 over 12.5
12.5 over 19
15 over 15
15 over 19
32
38
38
41
51
60
60
60
30
40
40
50
50
65
65
65
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F 00353 1 623 7054
E [email protected]
Timber joists ceilings and separating / compartment floors
T 00353 1 629 8400
6.5
319