Complete Guide to Buying GP Sheets: Grades, GSM & Pricing
Galvanised Plain (GP) sheets are among the most widely used steel products in India — from roofing and HVAC ducting to automotive components and cold storage panels. Yet many buyers struggle with understanding the specifications that matter most: zinc coating weight (GSM), thickness, and IS standards.
In this comprehensive guide, we break down everything you need to know to make an informed purchasing decision.
What is a GP Sheet?
A GP (Galvanised Plain) sheet is a cold-rolled steel sheet that has been coated with zinc through a continuous hot-dip galvanising process. The zinc coating serves as a sacrificial barrier, protecting the base steel from corrosion and rust — even in harsh outdoor environments.
GP sheets conform to IS 277:2008 (Indian Standard) and are available in coil and cut-sheet forms.
Understanding Zinc Coating Weight (GSM)
The most critical specification when buying GP sheets is the zinc coating weight, measured in grams per square metre (g/m² or GSM) on both sides combined. Higher GSM means more zinc and better corrosion resistance — but also higher cost.
| Coating Grade | Zinc Weight (g/m²) | Typical Use | Relative Cost |
|---|---|---|---|
| Z80 / 80 GSM | 80 | Indoor applications, general purpose | Lowest |
| Z90 / 90 GSM | 90 | Light outdoor, dry environments | Low |
| Z120 / 120 GSM | 120 | Standard roofing, ducting, enclosures | Medium |
| Z150 / 150 GSM | 150 | Heavy-duty outdoor, coastal proximity | Medium-High |
| Z180 / 180 GSM | 180 | Highway guardrails, industrial | High |
| Z275 / 275 GSM | 275 | Marine environments, extreme exposure | Highest |
Pro Tip: For standard roofing in Delhi NCR, Z120 (120 GSM) is the most cost-effective choice. For industrial or outdoor applications, Z180 or above is recommended.
Available Thickness Range
GP sheets are available in thicknesses from 0.14 mm to 2.0 mm (base metal thickness, excluding zinc coating). Common thicknesses include:
- 0.18–0.25 mm — Lightweight roofing, temporary structures
- 0.40–0.63 mm — Standard roofing, HVAC ducting, electrical panels
- 0.80–1.20 mm — Structural applications, automotive parts
- 1.50–2.00 mm — Heavy structural, cold storage panels
Width Options
Standard widths available at Aggarwal Steels:
- 600 mm, 760 mm, 900 mm, 1000 mm
- 1200 mm, 1250 mm (most common for roofing)
- 1500 mm (wide-width, premium)
Surface Treatments
- Regular Spangle + Passivated — Standard finish, visible zinc crystals
- Zero Spangle + Chromated — Smooth, uniform appearance
- Phosphated + Oiled — Best for subsequent painting or powder coating
How to Choose the Right GP Sheet
- Identify your environment — Indoor (Z80-Z90), outdoor standard (Z120), outdoor harsh (Z180+)
- Determine thickness — Based on structural requirement and span
- Consider surface treatment — Passivated for general use, phosphated if you plan to paint
- Check the maker — We supply GP from AM/NS India, SAIL, Tata Steel, JSW, and JSPL
- Specify edge type — Mill edge for coils, slit edge for cut-to-width
GP Sheet Pricing Factors
GP sheet prices in India are influenced by:
- Base HR/CR coil prices — The raw material cost
- Zinc premium — LME zinc prices directly affect coating cost
- Coating weight — Higher GSM = higher price per MT
- Thickness — Thinner gauges carry a rolling premium
- Width — Wider sheets (1500mm) cost more
- Maker brand — Tata/JSW may carry a brand premium over secondary producers
At Aggarwal Steels, we offer transparent, real-time pricing on our website. Configure your exact specification and see the per-MT price instantly — including GST breakdown.
Buy GP Sheets from Aggarwal Steels
We are one of Faridabad's largest stockists of GP coils and sheets, with ready inventory from all major Indian mills. Whether you need 1 MT or 100 MT, we deliver across Delhi NCR and pan-India with full GST invoicing.