The solar mounting structure is the part of a rooftop system that nobody asks about and everybody pays for twice if it is done badly. It decides how much of the roof you can use, whether the array survives a storm, and whether the owner can still walk on their own terrace. This guide covers the types used on Indian rooftops, the steel and galvanising to specify, wind and anchoring, and what it costs.
The four structures you will actually quote
Low-rise (standard) on an RCC roof
Modules sit 0.3–1 m above the slab on short legs. It is the cheapest option, the quickest to install and the easiest to clean. It suits a terrace the family does not otherwise use, and it keeps the wind load low because the array is close to the surface.
Elevated on an RCC roof
The array sits on a raised frame with roughly 2–2.5 m of clearance underneath, so the terrace stays usable for drying clothes, parking two-wheelers or storing water tanks. It costs more steel, needs deeper thought about wind and anchoring, and is what most urban Indian customers actually want once they realise they are giving up their roof. Elevated frames also let you run the array over a tank or a small room instead of designing around it.
Tin shed / metal roof
On a factory shed, rails clamp to the sheet profile or to the purlins, usually with clamps that avoid drilling through the sheet. The array follows the shed's own slope, so there is no row spacing to worry about and no shadow between rows. The engineering question shifts to the purlin spacing and the condition of the sheet — a twenty-year-old rusted sheet will not hold a twenty-five-year array.
Ground mount and carport
Used where there is open land or a parking bay. Ground mounts need foundations and a boundary; carports carry the extra requirement of looking presentable and keeping the vehicles dry. Both are outside the scope of a normal residential quote, but they turn up in commercial jobs.
Material: what to specify
- Hot-dip galvanised steel is the default for rooftop structures in India. Galvanise after fabrication so the cut ends and welds are coated, and specify the coating in microns in your bill of materials rather than writing "GI structure" and hoping.
- Pre-galvanised sections are acceptable for rails and smaller members, but every field cut and weld opens a path for rust, so they need touch-up with a zinc-rich compound.
- Painted mild steel is the false economy of this trade. It photographs well and fails at the joints.
- Aluminium rails are light, corrosion-proof and common on metal roofs; they cost more and need care where they meet steel.
- Stainless fasteners (SS 304) for module clamps and rail connections. Do not mix metals carelessly — aluminium against plain steel in a coastal monsoon is a corrosion cell.
Coastal sites deserve a level up: heavier galvanising, stainless hardware, and an honest conversation about replacing clamps in year ten.
Wind is what you are designing against
A tilted panel in wind behaves like a wing. The dominant force is uplift, not downward pressure, which is why an array can be torn off a roof it was comfortably heavy enough to sit on. The design pressure follows from the basic wind speed for the location under IS 875 (Part 3) — the map runs from about 33 m/s in the calmest zones to 50 m/s and above on parts of the east coast — adjusted for terrain, the height of the array above ground and the shape of the structure.
Two numbers decide whether the structure stays put:
- Uplift per support. Divide the array's uplift by the number of pedestals and compare it with the weight actually holding that pedestal down. On most elevated rooftop structures, uplift wins.
- Anchor capacity. Each pedestal is then anchored to the slab for the difference, commonly with chemical anchors, and the legs are braced so the frame does not rack.
PitchSun works this out from the customer's city and the array geometry and prints the anchor force per pedestal on the design, which is the number your site engineer actually needs. Whatever tool you use, the figure belongs in the drawing, not in someone's head.
Load on the slab
A rooftop array is a light load by building standards, but it is not nothing — and on an old slab the pedestals concentrate it.
- Modules and rails come to roughly 12–18 kg per m² of array.
- An elevated structure with concrete pedestals typically lands in the range of 40–80 kg per m² spread over the array footprint, most of it the pedestal concrete.
- What matters more than the average is the load per pedestal and where it sits. A pedestal over a beam is fine; a line of them mid-span on a forty-year-old slab deserves a structural opinion.
For an ordinary RCC roof in good condition, a standard rooftop array is comfortably within capacity. For old slabs, heavy elevated structures or anything unusual, get it checked — an article is not a structural certificate.
Steel and cost per kW
| Structure | Indicative steel per kW | Indicative cost per kW |
|---|---|---|
| Low-rise, RCC roof | 25–40 kg | ₹3,000–₹4,500 |
| Elevated, 2–2.5 m clearance | 40–70 kg | ₹5,000–₹8,000 |
| Tin shed / metal roof (rails and clamps) | Lower — no legs | ₹2,500–₹4,000 |
These are indicative ranges for planning, not a rate card. Structure cost moves with the steel rate, the galvanising rate, the wind zone, the height and how much fabrication is done in a workshop rather than on the roof. Price it from your fabricator's current quote — and remember that in a ₹45–₹55 per watt system, the structure is a small share of the money and a large share of the risk. For where the rest of the money goes, see rooftop solar cost per kW in India.
Layout: the part customers see
- Row spacing. Space rows so the front row does not shade the one behind it in winter, when the sun is lowest. The same array needs a wider pitch in Delhi than in Chennai, and shading a bottom row of cells can cost far more output than the panel's share suggests.
- Edge setback. Keep roughly a metre clear of the parapet where you can. It reduces wind effects at the edge and leaves somewhere to stand while cleaning.
- Walkways. Break long runs with a gap every several columns so the array can be cleaned and a faulty module can be reached without walking on glass.
- Tanks, stair rooms and dish antennas. Keep the array out of their winter shadow, and never block the door onto the roof.
- Tilt and azimuth. South-facing at a tilt near the site's latitude maximises annual output; lower tilts are common in high-wind and dusty areas and where roof space is tight.
Six mistakes that cost money later
- Painted MS instead of hot-dip galvanised — saves a few thousand rupees, rusts at the welds.
- Anchoring for weight instead of uplift — the array is fine until the first real storm.
- No bracing on elevated frames, so the structure sways and the clamps work loose.
- Pedestals cast on the waterproofing without treating the base, which turns into a leak the owner will blame on solar.
- Panels packed to the edge with no walkway, making cleaning unsafe and service expensive.
- Mixed metals without isolation, especially on coastal sites.
Every one of these is invisible at handover and obvious in year three. The structure is where an installer's reputation is quietly decided — and where an honest line item in the quotation separates you from the cheapest quote in the street. If you are still putting your bills of materials together by hand, our guide on starting a solar business in India covers the rest of the operating setup.
Frequently asked questions
Which solar mounting structure is best for an Indian rooftop?
On an RCC terrace, a low-rise structure is cheapest and an elevated structure is better when the family still wants to use the terrace or the roof has tanks and stair rooms to work around. On a metal or asbestos shed, rails clamped to the sheet profile are standard. The right answer comes from the roof, the wind zone and how the terrace is used — not from a catalogue.
How much steel does a rooftop solar structure need per kW?
As an indicative figure, a low-rise structure uses roughly 25–40 kg of galvanised steel per kW and an elevated structure with 2 to 2.5 m clearance roughly 40–70 kg per kW. Taller structures and higher wind zones push it up, because the members and the anchoring both have to grow.
What does a solar mounting structure cost in India?
Indicatively ₹3,000–₹8,000 per kW for a rooftop structure, with low-rise at the bottom of the range and tall elevated structures in high wind zones at the top. Prices move with the steel rate and with galvanising, so quote from your current fabricator rate rather than from a number in an article.
Should the structure be galvanised or painted?
Hot-dip galvanised. Paint on mild steel looks identical on day one and rusts at every welded joint within a few monsoons. Hot-dip galvanising after fabrication protects the cut and welded faces too, which is exactly where corrosion starts.
How is wind uplift handled on a rooftop structure?
Wind lifts a tilted array rather than pressing it down, so the anchors, not the weight, hold it. Design pressure comes from the basic wind speed for the site under IS 875 (Part 3), and each pedestal is anchored to the slab for the uplift it carries — commonly with chemical anchors — with the legs braced.
How much gap should be left between panel rows?
Enough that the front row does not shade the row behind it in winter, when shadows are longest. That gap follows from the site's latitude, the tilt and the table height, which is why the same array needs a wider pitch in Delhi than in Chennai.
