Metal roofing sheet cost per sq ft in India: colour-coated, Al-Zn and sandwich panels
How colour-coated, Al-Zn coated and insulated sandwich panel roofs are priced per sq ft in India, what thickness and BIS marking mean, and when a new structure is needed.
A metal sheet roof in India is priced per sq ft of roof area, and the biggest single question is whether the existing structure can be reused. Replacing sheets on a sound steel or timber frame is far cheaper than a new roof where the purlins, trusses and columns also have to be fabricated. The sheet itself is priced by thickness, coating and profile: a thicker colour-coated or aluminium-zinc (Al-Zn) coated steel sheet costs more than a thin one, and an insulated sandwich panel costs more again. As an illustrative guide, sheets fixed on an existing frame might run about ₹90–180 per sq ft before GST, a sheet roof with new steel structure ₹180–350, and an insulated panel roof more.
Part of roof and façade cost per sq ft in India.
Types of metal roof used on Indian homes
| Type | What it is | Illustrative rate per sq ft (before GST) | Suits |
|---|---|---|---|
| Galvanised (GI) sheet | Steel sheet with a zinc coating | Lower end | Sheds, temporary covers |
| Colour-coated (pre-painted) sheet | Galvanised or Al-Zn coated steel with a factory paint system | ₹90–180 on existing frame | Terrace sheds, sloping roofs, extensions |
| Al-Zn coated sheet (bare or colour-coated) | Steel with an aluminium-zinc alloy coating | Similar to or above colour-coated | Coastal and high-rain areas where corrosion matters |
| Insulated sandwich panel | Two metal skins with a foam or mineral wool core | ₹220–420 with structure | Rooms under the roof, where heat and noise matter |
| Sheet + separate insulation | Single sheet with an underlay or insulation layer below | Between the two | A cheaper way to reduce heat and drumming noise |
What drives the price of the sheet
Thickness: TCT versus BMT
Quotations quote thickness as TCT (total coated thickness, including zinc or Al-Zn and paint) or BMT (base metal thickness, the steel alone). A 0.50 mm TCT sheet has less steel than a 0.50 mm BMT sheet. Ask which one is quoted, and compare like with like.
Coating mass and paint system
The amount of zinc or Al-Zn coating, usually stated in grams per square metre, and the type of paint on top (for example regular polyester or a higher-durability system) affect life and price. Coastal and industrial areas need better coatings.
Profile and length
Trapezoidal, corrugated and tile-look profiles differ in cost and in how much cover width you get per sheet. Long single-length sheets reduce end laps, which are a common leak point.
BIS certification
Under the Ministry of Steel's Steel and Steel Products (Quality Control) Order, a number of steel products must carry the BIS Standard Mark. These include hot-dip galvanised sheets under IS 277 and continuously pre-painted galvanised sheets under IS 14246. Ask for the ISI-marked product and its test certificate. Check the current list of covered standards on the Bureau of Indian Standards site, because the list is amended from time to time.
What drives the price of the structure and fixing
- Reuse or rebuild. An engineer or experienced fabricator should check whether existing purlins and trusses are sound and adequate. Rusted or undersized members need replacement.
- Wind uplift. Coastal and cyclone-prone areas need closer purlin spacing, more fasteners and proper anchoring. Roof sheets that lift in storms are often a fixing problem, not a sheet problem.
- Fasteners and washers. Self-drilling screws with sealing washers, placed at the right spacing and not over-tightened, matter for leaks.
- Flashing and ridges. Ridge caps, wall flashings, gutters and downpipes are often quoted separately per running foot.
- Removal of the old roof. Taking down and disposing of old sheets, especially old asbestos cement sheets, needs care. Asbestos cement should not be broken or cut dry; ask your local body about safe disposal.
Illustrative comparison: 600 sq ft terrace shed
| Option | Rate (illustrative) | Roof cost | Gutters and flashing (lump sum) | Subtotal | GST 18% | Total |
|---|---|---|---|---|---|---|
| Colour-coated sheet on existing frame | ₹130 | ₹78,000 | ₹12,000 | ₹90,000 | ₹16,200 | ₹1,06,200 |
| Colour-coated sheet with new steel frame | ₹260 | ₹1,56,000 | ₹12,000 | ₹1,68,000 | ₹30,240 | ₹1,98,240 |
| Insulated sandwich panel with new frame | ₹340 | ₹2,04,000 | ₹12,000 | ₹2,16,000 | ₹38,880 | ₹2,54,880 |
Note that 600 sq ft is the sloping roof area, which is larger than the floor area it covers. For how to measure it, see the metal roof replacement worked example.
Permission before you build a shed
Replacing an existing sheet roof at the same height is usually treated as a repair, but a new terrace shed or a covered area may count as additional built-up area or a structure on the roof that the bye-laws restrict. In apartments it also needs society approval. See building permission for roof and façade alterations.
FAQ
Is a thicker sheet always better?
Thicker steel resists denting and spans further between purlins, but corrosion life depends on the coating and paint, and leaks depend on fixing and laps. Match thickness to purlin spacing and wind exposure.
Do metal roofs make rooms hotter?
A bare sheet heats up quickly in the sun and radiates heat into the room below. Insulated panels, underlays and ventilation reduce this. Light colours also help.
Can I put solar panels on a metal roof?
Often yes, with suitable clamps. Plan mounting with the roofer so that fixings do not puncture the sheet in the wrong places.
What GST applies to a sheet roof?
If the contractor supplies and fixes, it is generally a works contract at 18%. See GST on roofing, cladding and painting work.
Sources and where to check
- Bureau of Indian Standards — IS 277, IS 14246 and certification status of a licence
- Ministry of Steel — Steel and Steel Products (Quality Control) Orders
- CBIC GST portal — GST rates for steel products and works contracts
