05
Section 05
1ST FIX
CARPENTRY FIRST FIX
1.
2.
3.
4.
5.
6.
DPC to be installed under timber or metal stud wall sole plates and stairs.
Stairs to have 25mm continuous softwood packer between string and blockwork,
set packer below top of stair string by 25mm to allow plasterboard to fit neatly
between the string and blockwork.
The stair string must be fixed beneath the top and bottom tread first, working
from these top and bottom fixings, work towards the centre of the string.
100mm x 12 screws used in all instances
Install temporary handrail following installation of staircase.
Protect newel posts and tread nosings as a minimum.
OSB pattresses to be provided to support fittings such as radiators, towel rails,
sanitaryware, boilers, kitchen wall units (top and bottom fixings).
PLYWOOD NOT TO BE USED FOR PATTRESSES.
Boxings to be built square in 38mm x 50mm softwood. Where boxings are
adjacent to baths and showers ensure they project 50-100mm beyond the edge
of the bath or shower to allow satisfactory finishing of the junction.
7.
External doors must be fixed using correct fixings and brackets as illustrated on
3-5. Check manufacturer’s current recommendations.
8.
Door openings must be set out to achieve full width architraves.
9.
Protection to front doors, door frames, window boards and newel posts.
10. Noggins to be installed at least 1100mm from floor.
Not required for wet rooms where stud centres are reduced to 400mm.
11. All end studs to block work to be fixed with plugs and screws as per
specification.
ELECTRICAL FIRST FIX
1.
Holes to be cut and positioned within safe zones in the joists.
Refer to NHBC Standards 6.4.18 and manufacturer’s information.
2.
Cables must be installed vertically, horizontally, through sockets and
switches and clipped correctly.
3.
Back boxes must be installed to same heights, minimum 50mm consistent
space between others. Deeper back boxes must be chased into wall to achieve
flush board sticking.
4.
Extractor isolation switch to be centred above door head, outside room with fan.
5.
Metal plates to be installed to protect cables on timber stud.
6.
Media plate to be provided as standard in all lounges including TV, BT and power
sockets. (Satellite to be included as standard in apartments only). In addition
where BTOR is installed on the site a RJ45 (Cat 5) module should be fitted.
7.
Light switch back box to be fitted 150mm centre from structural opening.
8.
Light pendants to have solid noggin support.
9.
Complete wiring as per kitchen layout.
10. Fit only metal back boxes on external block walls and CLS stud walls, where
installed on CLS studs walls these must be supported on timber noggins and set
forward 5mm. No dry wall boxes.
11. Extractor fan ducting to be correct size and positioned as per ventilation layout.
Verplas rigid ducting to be used in all cases.
PLUMBING FIRST FIX
1.
Gas carcass feeding boiler must be chased (maximum 25mm) into blockwork
and fully bedded/pointed into blockwork. Solid dab over pipework.
See pages 5-14, 10-9 and 10-10.
2.
Fit soil vent pipes and protect at First Fix stage, to be clipped to wall
minimum 2 per storey, plus loft space.
3.
Radiator Manthorpe manifold to have solid noggins and 4no. fixings used.
4.
Basin feeds must exit wall maximum 100mm below underside of basin and
waste inside pedestal. Feeds to towel rails must exit wall, level and at correct
height.
5.
All pipework must have felt/lagging where it touches timber/metal to prevent
knocking (floors & studs)
6.
Pipework must be clipped within joist voids to manufacturer’s guidance.
7.
Minimise excessive use of flux, wipe off all joints at completion.
9.
Fit fire collars to SVP flush with underside of slab where required.
10. Pressure test system including Gas pipes after First Fix complete.
1st FIX
Display housetype working
drawings in each house for easy
reference.
05
To ensure consistently accurate
loft openings, utilise a reusable
profile.
Ensure pattressing is OSB and
appropriately sized. Plywood is
not to be used for pattresses.
DPC to be installed under stud
wall sole plates.
CONSTRUCTION BEST
PRACTICE GUIDE
5-1
05
1st FIX
Ensure DPC placed under first
stair riser. During installation
screw fix 50mm x 38mm timber
tight to 1st riser using 4no
75mm x 10 screws and plugs to
secure stair flight until it is fully
fixed.
During installation, adequate
studwork to be installed to fix
plasterboard to. Pack stairs
25mm off blockwork wall to
allow plasterboard to fit flush
inside string.
5-2
Ensure stairs are accurately
positioned with treads square to
newel posts prior to fixing. This
is of particular importance on
winder treads.
Continuous 25mm packer
between blockwork and stair
string.
CONSTRUCTION BEST
PRACTICE GUIDE
1st FIX
05
DO NOT ACCESS THE STAIRS UNTIL THEY ARE FULLY FIXED FROM BELOW
MASONRY FIXING
Drill through stairs into block
work, then screw fix with
100mm x 12 screws used
unless alternative specified.
The stair string must be fixed
beneath the top and bottom
tread first, working from these
top and bottom fixings, work
towards the centre of the string
at maximum 600mm centres.
TIMBER FIXING
Timber stud wall to be built
prior to installation of stairs
Timber stud to be formed at
300mm centres, stair string
to be fixed into vertical studs
with 100mm x 12 screws used
(unless alternative specified)
at no greater than 600mm
centres.
The stair string must be fixed
beneath the top and bottom
tread first, working from these
towards the centre of the string.
Note when working towards the
centre a horizontal noggin may
be required to catch the centre
fixing.
Bolts/Fischer fixings to be used
only if specified.
CONSTRUCTION BEST
PRACTICE GUIDE
5-3
05
1st FIX
Stairwell pattresses to be
installed flush between studs
where internal handrail to be
fitted 900mm above stairs.
Also removes fall risk during
construction.
Install OSB pattress to allow for
easy handrail fixing.
Noggins to be installed at least
1100mm vertical height to
centre.
The top nosing and newel
post must be fixed to the joist
trimmer, and flooring must be
fitted tight to stair nosing.
5-4
CONSTRUCTION BEST
PRACTICE GUIDE
1st FIX
05
When fixing vertical studs to
blockwork ensure screw fixings
are used to ensure a good
fixing.
Stairs to be adequately
protected from damage during
construction. Not to be removed
until decoration.
50mm minimum thickness
mineral fibre quilt to be
installed in partitions between
bedrooms and any room
containing a WC. If tiling
required to bathroom side
install studs at 400mm centres.
CONSTRUCTION BEST
PRACTICE GUIDE
5-5
05
1st FIX
38mm softwood pipe boxing. Void
to be filled with minimum 25mm
sound deadening material around
soil pipe, zip tied. WWHR or AAV
valves should not be lagged. See
Standard Detail DB-SD09-001.
OSB pattresses to be
installed to allow easy
fixing of kitchen units.
5-6
Seal all areas at the earliest
opportunity for future air
tightness testing.
Media plate used instead of
multiple sockets, aerials etc.
As per working drawings. Cable
clips to be installed at every
mortar joint.
CONSTRUCTION BEST
PRACTICE GUIDE
1st FIX
05
MEDIA PLATES
In houses install TV and BT
point as standard; in addition
where BTOR is installed on
the site a RJ45 (Cat 5) module
should be fitted.
In apartments install TV, BT
and satellite points as standard;
in addition where BTOR is
installed on the site a RJ45
(Cat 5) module should be fitted.
CONFIRM SPECIFICATION WITH YOUR TECHNICAL DEPARTMENT.
Light pendants to have 75x50mm
noggin 200mm long cut at 45º,
where adjacent to a joist.
CONSTRUCTION BEST
PRACTICE GUIDE
Where light positions do not
fall adjacent to a joist ensure
adequate support is installed.
5-7
05
1st FIX
Steel plate must be used to
protect services where they pass
through studwork. Identification
tape to be used between studs.
Sheathing is not required.
Ensure front doorbell is fitted to
the centre of the doorframe on
the lock side of door.
5-8
TV aerial connection to be
clearly marked and easily
accessible in loft space.
All cables passing through
masonry to be installed in a
sleeve.
CONSTRUCTION BEST
PRACTICE GUIDE
05
1st FIX
Deeper back boxes must be
chased into wall to achieve
flush board sticking.
Do not fit shaver socket directly
above washbasins, allow for
mirror/cabinets.
Max 50-60mm
Always maintain a minimum
spacing of 50mm between
sockets. Use a single gang box
as a spacer during first fix.
CONSTRUCTION BEST
PRACTICE GUIDE
Ensure electrical fittings are
set out square and consistently
spaced throughout.
5-9
05
1st FIX
Extract of DB-SD10-007 shown. For further information refer to
Standard Details DB-SD10-006 and DB-SD10-007.
Apply a generous bead of Polymer Mastic to all raised rib areas, the waste area
and especially around each foot pad location area on the underneath of the tray.
Ensure the depth of the Polymer Mastic bead is sufficient to extend beyond the tray
rim height (approx. 20mm) to have good contact with the floor. A generous bead of
Polymer Mastic must then be applied around the exterior rim of the tray as shown.
Before final fitting add a generous amount of Silicone to the faces of the tray that
will contact with your walls to create a good seal.
5-10
CONSTRUCTION BEST
PRACTICE GUIDE
1st FIX
05
Extract of DB-SD10-006 shown. For further information
refer to Standard Details DB-SD10-006 and DB-SD10-007.
Ensure only Merlyn
DWAS 90mm Hi Flow
Shower Waste is
used and is fitted as
per manufacturer’s
instructions.
CONSTRUCTION BEST
PRACTICE GUIDE
Install 9mm plywood to sides
of shower tray to allow for
plasterboard. Leave 10mm
off blockwork to allow for
plasterboard adhesive.
5-11
05
1st FIX
For wet room areas to be tiled
use 63mm x 38mm studs
installed at 400mm centres.
This does NOT require mid-rail
noggins. See DB-SD03-005 and
NHBC Standards 9.2.4 Table 9.
All pipework to be capped
off during construction. Bath
legs to be securely fixed on
a minimum of 100x25mm
bearers. OSB shown here to
support bath.
(Does not require painting.)
All other ventilation
penetrations to be built in.
Cavity Tray required above.
Flue openings to be cored on
site as required.
5-12
CONSTRUCTION BEST
PRACTICE GUIDE
1st FIX
05
Accurately position boiler
pipework at first fix.
Boilers should always be
mounted on external walls.
No concealed flues. Fixing
templates should be utilised. All
pipes to be tested prior to boiler
being fitted including gas pipes.
CONSTRUCTION BEST
PRACTICE GUIDE
5-13
05
1st FIX
Gas pipe to be clearly marked
and adequately supported in
joist zone. Felt installed to
prevent squeaking.
Gas Safe Technical Bulletin
number 113, confirms that
no additional ventilation is
required for gas pipework in
modern joisted floors, in single
dwellings, as there is sufficient
advantageous ventilation.
Gas pipes to be fully bedded/
pointed into blockwork.
5-14
Plastic coated gas pipe to be
recessed in to wall by max
25mm, then covered with
mortar. To be solid dabbed
when plastered.
Gas pipe to be mortared over
then covered with solid dabs.
Cables clipped at every course.
CONSTRUCTION BEST
PRACTICE GUIDE
1st FIX
05
All plastic plumbing to have
detection tape behind.
Correctly installed water
service pipe insulated and
capped off to prevent any
chance of blockage.
CONSTRUCTION BEST
PRACTICE GUIDE
Pipework to be equally spaced
and fixed and clearly labelled
following heating design.
5-15
05
1st FIX
Ensure pipework is adequately
fixed with clips installed in line.
5-16
Correctly installed radiator
boss. OSB to be utilised to
ensure tight seal against foam
gasket with the plasterboard.
CONSTRUCTION BEST
PRACTICE GUIDE
1st FIX
Feeds to towel rails must exit
wall level, at correct height and
be finished with a pipe rose.
TRV to face away from towel
rail.
05
Basin feeds must exit wall
maximum 100mm below basin
and waste inside pedestal.
(Copper pipes to be wrapped
in PVC tape prior to being
mortared over.)
Accurately position ½” copper
WC cold water feed as high
as possible, generally 300mm
from the floor and 125mm from
centre of outlet to ensure the
pipe isn’t visible once the WC is
installed. Isolation valve to be
fitted and accessible.
CONSTRUCTION BEST
PRACTICE GUIDE
5-17
05
1st FIX
Soil vent pipes to be clipped and
screwed to wall minimum 2 per
storey, plus loft space.
Soil vent pipe rodding eyes to
be at correct height and facing
the right way. Ensure insulation
doesn’t cover AAV’s/Durgo.
Radiator Manthorpe manifold
to have solid noggins and 4no.
fittings used.
In apartments fit fire collars
to SVP flush to underside of
slab, as defined on working
drawings.
5-18
CONSTRUCTION BEST
PRACTICE GUIDE
1st FIX
05
Pattress support for extract
fans with mastic seals to
ensure optimum air tightness.
Soil vent pipe to be clipped to
wall minimum 2 per storey, plus
loft space.
SVP turned back into roof void
to aid visibility. Condensate
cap fitted at pre-plaster stage.
Ensure height allows for
insulation.
CONSTRUCTION BEST
PRACTICE GUIDE
Roof ventilators to be fully
fixed to terminals in line with
manufacturer’s instructions.
Usually fixed with jubilee clip
and then taped.
5-19
05
1st FIX
Ensure site specific ventilation
strategy is followed. Duct
runs must not exceed
manufacturer’s instructions.
Neat installation of ducting and
fire wrap in apartments.
Ensure correct components
are used for installation of
kitchen extractor run which
is adequately supported and
sealed.
Ensure sleeved penetration for
ventilation is installed centrally
to allow a symmetrical finish
later.
5-20
CONSTRUCTION BEST
PRACTICE GUIDE
1st FIX
Window Boards should be
securely fastened, with
brackets screwed not nailed
and neatly pointed underneath.
To achieve a minimum of 25mm
overhang from finished plaster
face.
05
Windows to be fixed at head.
over each mullion.
Window formers to be used to close cavity. Requirement for fixing
cleat to be fixed to former and blockwork 150mm from corner and
at 600mm centres vertically.
CONSTRUCTION BEST
PRACTICE GUIDE
5-21