b-1 tender form - Maharashtra Industrial Development Corporation

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No deduction shall be made for bolt holes (excluding holes for anchor or holding down bolts)
The weight of steel sheets, plates and strips shall be taken from relevant Indian Standards based on
7.85 kg/m2 for every millimeter sheet thickness. For rolled sections, steel rods and steel strips, weight
given in relevant Indian Standard shall be used.
The contract rate shall be per Metric tonne weight of the component fabricated and measured as
above, correct to a 3 decimals (one gram).
Item No 17 Providing 6 mm thick asbestos cement corrugated sheet conforming to IS:459-1992, for
roofing and laying the same in position as per the stipulation in IS:3007-1991 including galvanised iron
L or J hook bolts, and galvanised iron and bituminous washers, galvanised iron clamps, nuts and bolts
etc. complete.
4.1 General : The item pertains to providing and fixing the roofing of Asbestos Cement
Corrugated Sheets (A.C. Sheet roofing).
4.2 Material : The A.C. corrugated sheets shall be of the approved quality and shall conform to
IS:459. The sheets shall be free from cracks, chipped edges or corners and other damages.
4.3 Laying :
1. The sheets shall be laid on the purlins and other roof members as indicated in the
working drawings or as instructed by the Engineer-in- Charge.
2. The maximum spacing of purlins under the sheets shall be 1.40 metres in the case of 6mm
thick sheets and these shall in no case be exceeded. Ridge purlins shall be fixed at 75 mm to 115
mm from the apex of the roof.
3. The top bearing surfaces of all purlins and of other roof members shall in one plane so that
the sheets when being fixed shall not require to be forced down to rest on the purlins. The finished
roof shall present a uniform slope and the line of corrugations shall be straight and true. The sheets
shall be laid with the smooth side upwards.
4. The sheets shall be laid with a side lap of half a corrugation and an end lap of 15 cm
minimum in the case of roof with a pitch flatter than 1 vertical to 2.5 horizontal (approx. 22 degree)
or in the case of very exposed situations, the minimum permissible end lap shall be 20 cms.
Side slaps should be laid on the side facing away from the prevailing monsoon winds.
5. The free overhang of the sheets at the eaves shall not exceed 30 cm. Corrugated sheets shall
be laid from left to right starting at the eaves. The first sheet shall be laid uncut but the remaining
sheets in the bottom row shall have the top left hand corner and bottom right hand corner cut for the
half the corrugation and length equivalent to overlap as per manufacturers code of practise. The last
or top row sheets shall all have the bottom right corner cut with the exception of the last sheet which
shall be laid uncut. If for any reason such as on considerations of the direction of prevailing winds,
laying is to be started from the bottom right hand corner, then the whole procedure should be
reversed.
6. The method described above is necessary to provide a snug fit where four sheets meet at a
lap. It is cut from a point 15 cm (or whatever the length of the end lap may be) up the vertical side of
the sheet to a point 5 cm along the horizontal edge. The cutting may be done with an ordinary wood
saw at site.
4.4 Fixing :
1. Sheets shall be secured to the purlins and other roof members by means of 8mm diameter
galvanised iron J or L hook bolts and nuts. While, J hooks are used for fixing to angle iron purlins, L
hooks are used for fixing to RS joists, timber or precast, concrete purlins. The grip of the J or L hook
bolt on the side of the purlin shall not be less than 25mm. Each galvanised iron J or L hook bolt shall
have a bitumen washer and a galvanised iron washer placed over the sheet before the nut is screwed
down from above. On each purlin there shall be one hook bolt on the crown adjacent to the side lap
Contractor.
Executive Engineer(E&M).