BUILDER’S WORK

BUILDER’S WORK
PART I -GENERAL
A. Builder’s Work Generally: materials and workmanship, unless otherwise
specified, are to be in accordance with the relevant requirements of the
Specification for structural and Architectural work.
B. Description of Work: cable and duct trenches, equipment foundations, bases
and supports, ducts and duct banks, manholes, handholes and earth pits,
chases, holes and the like, sleeves, bolts, brackets and fixings including
grouting.
C. Coordination: confirm locations and dimensions of all builder’s work
required for electrical work. Submit shop and construction drawings or other
data to the Engineer for checking before proceeding with the work.
D. Routes For Services Below Ground: agree precise locations with the
Engineer, set out clearly and accurately and locate with temporary marker
posts.

PART 2- PRODUCTS AND MATERIALS
2.01 Components
A. Polyvinyl Chloride (PVC) Heavy Gauge Ducts: to BS 6099-section 2.2 for
outdoor power and lighting cable installations are to be non-sparking type,
suitable for direct burial in ground, minimum tensile strength 500 kg/cm2,
impact strength 5kg/cm2, supplies in standard 6m lengths, with one end of
each length tapered. Ducts are to be nominal size shown on the Drawings,
with minimum wall thickness 3.2mm for 100mm ducts and 4.7 mm for 150
mm ducts.
B. Duct Supports: pre-formed, non-metallic of approved type. Supports
containing metal are to have the metal non-continuous and not forming a
magnetic loop in any manner.
C. Cover For Trenches in electrical rooms and the like, unless otherwise
specified or shown on the Drawings, are to be flanged chequered steel plates
with angle or channel section frames, suitably reinforced to support
anticipated loads, and finished with zinc chromate primer and two coats grey
enamel.
D. Covers For Manholes and Handholes: to BS 497, chequered cast iron or cast
steel, recessed type, and of suitable duty for the particular application.
E. Brackets, Supports, Rails and Tracks for supporting electrical installations
are to be galvanized steel, fixed with expansion bolts of approved for specific
light duty installations.
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F. Opening For Culvert each opening shall be as shown on drawings with gasket
frame from all sides for water and dust protection. The cover shall be precast
reinforced concrete suitable for any moving loads.
2.02 Composite Construction:
A. Equipment Foundations and Bases: reinforced concrete, as approved by the
Engineer after submission of design calculations. Dimensions, levels and
surface finishes are to be suitable for equipment installed, as shown on the
Drawings or in accordance with approved shop and construction drawings.
B. Concrete Envelope For Duct Banks for power distribution systems and
outdoor lighting cable installations crossing water, gas and sewage mains,
under roadways and where required or shown on the Drawings, is to be
reinforced concrete Class B using sulphate-resisting Portland cement.
Reinforcement is to consist of 12 mm diameter longitudinal bars at
approximately 300 mm centers along bottom and sides of duct bank with
10mm diameter U-shaped transversal bars at 400mm centers. Length of
concrete envelope is to extend at least 300mm beyond side of crossing etc.
C. Cable Manholes and Handholes: reinforced concrete Class B suing
sulphate-resisting Portland cement, with approved waterproof membrane on
external surfaces, and with cable supports where necessary, pull-eyes, and
drain pit and drain pipe as required. Dimensions and reinforcement are to be
as shown on the Drawings or in accordance with approved standard details
shown on shop and construction drawings.
D. Culvert: refer to structural specifications and drawings.
PART –3 WORKMANSHIP
3.01 Generally
A. Cable Trenches: width is to be as small as practicable with sides vertical.
Remove mud, rock projections, boulders and hard spots from trench bottom
and trim level. Inform the Engineer in advance to give him reasonable
opportunity to inspect trench for each section of the work.
B. Directly Buried PVC Cable Ducts:
- Lay and join ducts to required line and level on sand bed, cover with sand
and backfill trench to ground level with excavated soil, free from stones
and other debris, well compacted in layers not exceeding 300 mm thick
- Lay approved concrete tiles to fully cover cable duct, extending minimum
50mm beyond sides of duct and placed 300mm below ground level.
- Provide warning tape or galvanized steel mesh along duct runs at a depth
200mm below ground level.
C. Underground Cable Duct Assemblies:
- Form duct assembly to required line and level, using duct supports spaced
to prevent sagging of ducts and breaking of couplings and watertight
seals, and secured with cords(not tie wires) where necessary.
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- Provide 1% slope to duct banks for draining to exterior manhole,
handhole or other location as instructed.
- Join ducts using waterproof cement, to manufacturer’s recommendations,
to give waterproof and sand proof joint with at least 80mm overlap.
- Provide 3mm galvanized steel wire inside empty ducts, for future pulling
of cables, extending 1 m beyond duct banks at both ends and securely
fixed to wooden bungs sealing the duct.
D. End of Ducts: ducts ending in cable manholes or handholes are to be neatly
cut and reamed and set behind chamfered precast concrete duct end blocks or
terminated with appropriate bell-mouth bushing set in concrete wall. Ducts
not ending in cable manholes or handholes are to be properly capped.
E. Sealing Ends of Ducts : conduits and ducts, active or spare, at entry into
building or manhole, are to be completely sealed with approved plastic
moulds or wooden bungs to prevent entry of rodents, gas and vapor.
F. Sleeves or Ducts in Equipment Foundations are to be provided, whether
shown on the Drawings or not, and in accordance with approved shop and
construction drawings or as instructed by the Engineer. Obtain approval of
sleeve or duct installation prior to concreting.
G. Support Frames For Switchgear located over cable trenches, where shown on
the drawings or required by equipment design, are to be installed prior to
concreting.
H. Drilling for Anchor Bolts is to be carried out using appropriate electric drills
and in approved positions.
I. Holes and Chases in Situ Concrete are to be cast in. Do not cut hardened
concrete or drill holes large than 10mm diameter without prior approval.
J. Holes and Chases in Precast Concrete: do not cut or drill precast concrete
without approval.
K. Holes in Structural Steelwork: do not cut or drill structural steelwork without
prior approval.
L. Holes and Chases in Masonry must not exceed:
Size of holes : 300mm square
Depth of vertical chases : 1/3 wall thickness or, in cavity
walls, 1/3 leaf thickness
Depth of horizontal chases : 1/6 wall or leaf thickness.
M. Cutting Masonry:
- Ensure mortar is fully set before commencing
- Cut carefully and neatly, avoiding sapling, cracking or other damage to
surrounding structure.
- Keep holes to smallest practicable size and do not exceed specified
dimensions cut chases in straight lines and horizontally and vertically
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only do not set back to back, offset by a distance not less than wall
thickness.
N. Preformed Holes in Masonry: submit proposals for bridging over holes for
ducts etc. which exceed 460 mm with.
PART 4- INSPECTION AND CLEANING
A. Inspection of Duct Systems: directly buried ducts and underground duct
assemblies are to be inspected in the presence of the Engineer, before
backfilling or concreting. Steel mandrel or other approved device, diameter
equal 90% of inside diameter of duct and 500mm long, is to pulled through
entire run of duct and is to pass through without getting stuck. Ducts which do
not allow mandrel to be pulled through are to be repaired or replaced to the
satisfaction of the Engineer.
B. Clean Ducts with stiff bristle brush pulled through each duct prior to pulling
in cables.
END OF SECTION 16900