Guides
Colour coated vs GC (tina) chadra
GC (tina) chadra is bare galvanised steel rolled into corrugations and colour chadra is steel painted on the coil and then rolled into square ribs, so the two will never lap into one another on one roof.
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Both are steel roofing sheet, both screw down onto the same purlins, and after that they part company. Jay Shree Infra deals in the two at its Saharsa godown: the plain tina at 0.30 and 0.45 mm, and the colour at 0.35, 0.45 and 0.47 mm, both in 6, 8, 10, 12, 16, 18, 20 and 22 ft with other lengths made to measure. Tata Shaktee, Bokaro and Jindal are the names the plain chadra reaches this counter under, and Tata Durashine, Jindal and Kamdhenu the colour. Not every length is in every brand on a given day, so say the length with the brand when you ring. Workshops, godowns and village PACS godowns across Saharsa, Supaul and Madhepura go up under both.
The choice gets made once, before the frame is loaded, because a corrugated sheet and a ribbed sheet have no lap in common. Below is what each maker publishes for its own sheet, where the two sit in the 2024 quality control order, and what has to be settled on the phone. Size by size, the sheets themselves are on the GC sheet (tina chadra) page and the colour chadra page, and the purlins, ridge, flashing and screws that go under and around both are on the roofing and shed page.
Published figures
What each maker prints for its own sheet
Width, cover, thickness and the standard behind four sheet lines, in the figures their makers print for them.
Scroll the table sideways to see every column
| Sheet | Overall width | Effective cover | Published thicknesstotal painted | Standard in the 2024 Order |
|---|---|---|---|---|
| Tata Shaktee Wide | 910 mm | not published; the lap decides | not published by the maker | IS 277:2018 |
| Tata Shaktee Wider | 1220 mm | not published; the lap decides | not published by the maker | IS 277:2018 |
| Durashine Roof | 1072 mm | 1015 mm | 0.37, 0.47, 0.52, 0.62 mm | IS 14246:2013 / IS 15965:2012 |
| Durashine Wall | 1150 mm | 1110 mm | not published by the maker | IS 14246:2013 / IS 15965:2012 |
Tata prints two Shaktee widths, one against each of two products it names, and counts the corrugations across both, 13 on the Wide sheet and 15 on the Wider. Tata Shaktee Standard is a third product on the same page, and no width, thickness, length or coating figure is published against it: the 800 mm that appears there sits inside a sentence comparing Shaktee to ordinary 800 mm GC sheet, and belongs to that ordinary sheet, not to Shaktee Standard. Confirm a Shaktee Standard bundle's size on the call. The last column is the entry each sheet sits at in Schedule 1 of the Steel and Steel Products (Quality Control) Order, 2024, S.O. 3716(E).
Read the width columns in pairs. On the plain sheet Tata publishes what a tape reads across the sheet and stops there, because how much of it lands on your purlins follows how many corrugations you slide over the next sheet. On the colour sheet that lap is built into the profile, so Tata Steel Colors publishes both figures, 1072 mm across and 1015 mm of cover on the roof profile. A colour roof gets counted off the cover figure and a tina roof off the width less whatever lap has been decided, which is two different sums for one roof.
The mark
One order, two entries, two different licences
The Steel and Steel Products (Quality Control) Order, 2024, S.O. 3716(E) of 29 August 2024, covers both sheets and covers them apart from each other. Galvanised steel strips and sheets, plain and corrugated, are IS 277:2018 at serial 7 of Schedule 1. Continuously pre-painted galvanised steel sheets and coils are IS 14246:2013 at serial 33. Pre-painted aluminium zinc alloy metallic coated steel is IS 15965:2012 at serial 34. None of the three entries carries a size exclusion.
So an ISI mark on a tina bundle and an ISI mark on a painted coil are licences held against different standards, and one of them tells you nothing about the other. Tata states that Shaktee is ISI certified under BIS. On a colour load the live question is which of the two colour serials the certificate names, because zinc under the paint and a zinc aluminium alloy under the paint are two entries, and the shade on top says nothing about which. Tata Steel Colors publishes Durashine as zinc aluminium alloy coated steel, and on any other colour line the mill's certificate is what settles it.
The figure everybody compares
Which steel a thickness figure is counting
Base metal thickness is the steel by itself. Total painted thickness is that same steel with its metallic coating and its paint on both faces counted in. Durashine's four published figures, 0.37, 0.47, 0.52 and 0.62 mm, are the second kind, and Tata Steel Colors labels them so. Ask which basis a figure is on rather than assume it, tina or colour, and we confirm it on the call.
0.45 mm sits on both the tina list and the colour list, and that coincidence is where the trouble starts. The same three digits describe two different sheets, and where one of them is counting paint the steel underneath it is thinner than the steel in the other. Ask what each quote is measuring, on both quotes, and ask before the two go side by side.
Shape
A wave and a rib do not nest
Corrugation is a continuous wave, and it closes by sliding one crest over the next, so how much sheet is left over is decided up on the roof. Tata Steel Colors describes the Durashine roof profile as a square fluting, with an anti-capillary groove and a widened valley to move water off, and the side lap on it is designed into the shape. Lay the two on one plane and neither lap closes.
That is worth knowing most on a roof that is already standing. Adding to a tina roof means tina in the same profile and the same width family, and Tata publishes two of its own, 910 mm with 13 corrugations and 1220 mm with 15. Turning a standing roof over to colour means a whole plane of it, which belongs to the fabricator and is no longer a patching job.
Slope belongs to the sheet as well. Tata Steel Colors puts 5 degrees on the Durashine roof sheet as the least fall it is published for, and publishes its wall sheet as a separate profile at 1110 mm of cover on a 1150 mm sheet, made to project lengths. The Shaktee page publishes no slope figure at all, so there is nothing on it to carry across to a tina roof. Take that figure from the mill whose sheet is actually going up, and hand it to the fabricator with the span.
What goes with it
The screws follow the sheet
Tata Steel Colors publishes its own fixing guidance for Durashine and it is specific about the fastener: class 3 screws with EPDM rubber sealing washers, and it tells the installer to keep stainless steel screws, J hooks and carbon washers off the sheet. The same guidance publishes pre-crimped curves at 273 mm and 469 mm typical, subject to what is available locally, so an arched run gets bought already curved. Whoever made the sheet you are buying publishes a list of its own, and what we hold of Durashine's is on the Tata Durashine page.
We stock one set of fittings for both sheets: purlins and girts, ridge and flashing, self drilling screws, sealant, gutters, ventilators and daylight sheets. The list reads the same for the two, and a ridge is cut to the profile it closes over, so say which sheet the fittings are going onto when you order them.
Beyond these two makers
What two makers publish, and what needs a call
Two makers publish enough for a table and the rest of both racks does not. Bokaro on the plain side is one of SAIL's own plants, and the two widths above come off Tata Steel's own Shaktee line. Jindal and Kamdhenu come in on the colour side, and neither publishes a sheet specification that lines up with Tata's figures, so do not carry a Shaktee or Durashine number onto either brand: confirm their sizes on the call.
What is standing today, in which length, thickness and colour, is a call, not a published figure. A 22 ft sheet also picks the vehicle before the quantity does, on all 34 blocks of Saharsa, Supaul and Madhepura.
Sources
The two makers and the order behind these figures
Every figure above comes from one of these four: the two sheet pages their makers publish, the fixing guidance for one of them, and the gazetted order that puts both sheets under the ISI mark.
- Tata Shaktee GC sheets, with the two published widths and the corrugation countsTata Steel
- Tata's own Durashine sheet page, carrying the painted thickness figures, both cover widths and the 5 degree slopeTata Steel Colors
- Durashine fixing and maintenance answers, with the fastener class and the crimp radiiTata Steel Colors
- Steel and Steel Products (Quality Control) Order, 2024, Schedule 1 as gazettedMinistry of Steel
Questions
Kaun si chadra, tina ya colour
Shed ke liye tina chadra lein ya colour chadra?
Both go over the same purlins, so the frame does not choose for you. What chooses is that they are different products under different entries of the 2024 Order, IS 277:2018 on the plain sheet and IS 14246:2013 or IS 15965:2012 on the painted one, and their profiles will never lap into each other. Say which of the two the shed is going in when you ring, because that one word fixes the profile, the fittings and the sheet count.
0.45 wali tina aur 0.45 wali colour, ek hi motai hui?
Not necessarily, and the figure alone cannot tell you. Total painted thickness counts the metallic coating and the paint on both faces, base metal thickness counts only the steel, and Tata Steel Colors publishes Durashine on the first basis at 0.37, 0.47, 0.52 and 0.62 mm. Ask which basis a number is on before two matching figures are treated as one sheet.
Purani tina chhat par colour chadra jod sakte hain?
Not into the same lap. A corrugated sheet closes by sliding a wave over a wave, and the Durashine roof profile closes on a designed side lap in a square fluting, so the two edges never meet. Colour on a tina roof means a full plane of it, planned by the fabricator. Measure one old sheet and give us the width and the wave count first.
Dono me screw ek jaise lagte hain?
Take the fastener from the maker of the sheet. Tata Steel Colors publishes class 3 screws with EPDM rubber sealing washers for Durashine and tells installers to keep stainless steel screws, J hooks and carbon washers off it. We stock self drilling screws for both sheets, and the ridge, flashing and sealant go on the same order.
Colour sheet 16 foot se lambi banwa sakte hain?
Ask on the call, because past the maker's published lengths it turns on what has come in. Tata Steel Colors publishes Durashine roof sheet in standard lengths of 8, 10, 12, 14 and 16 ft. We stock eight lengths up to 22 ft on both sheets, and anything outside it is made to your measurement against whatever that brand has arrived at, so it is settled before a sheet is cut. Give us the span and the village along with the length.
Before you order
Settle these before the frame is loaded
The sheet answers none of these by itself, and every one of them is cheaper to settle before the load leaves than after it lands.
What is on that roof now, and how wide is one of those sheets?
A tape across one old sheet, and the number of waves in it, tell us which family it belongs to. A ribbed colour sheet will not close into a corrugated lap, so this decides whether the job is a patch or a plane.
Is the thickness on this quote the bare steel or the painted total?
Durashine is published as total painted thickness. Ask which basis a figure is using before you compare it, tina or colour: we confirm it on the call. Two quotes reading 0.45 can be two different sheets until this is answered.
Which standard does the certificate on this load name?
IS 277:2018 on plain galvanised sheet, IS 14246:2013 or IS 15965:2012 on colour, at serials 7, 33 and 34 of the 2024 Order. Ask what came in with the load.
What screws and washers does the maker publish for this sheet?
Tata Steel Colors names class 3 screws with EPDM sealing washers for Durashine and rules out J hooks and carbon washers. Take the list from the maker of the sheet you are actually buying.
How long does the run need, and does it have to be one sheet?
We stock up to 22 ft on both, with anything past it made to measure. Durashine's published standard roof lengths run 8, 10, 12, 14 and 16 ft, so a longer colour sheet is a question about what has come in.
Contact
Name the sheet before the frame goes up
The two never share a lap, so a roof plane is committed to one of them the day the first sheet goes on. Ring +91 6202 967 218 with the span, the length, the thickness and which of the two the plane is going in, and the cutting, the count and the vehicle are all settled against that one word.
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