Case Study: 250kW Concrete Ballasted Flat RCC Roof Installation in Trichy
Project Overview
- Capacity: 250 kWp
- Location: Manachanallur Industrial Corridor, Trichy, Tamil Nadu
- Roof Type: Flat Reinforced Cement Concrete (RCC) Roof slab
- Target Wind Speed: 47 m/s (Zone 4, IS 875 high-wind zone)
- Structural Solution: Non-penetrative Hot-Dip Galvanized (GI) steel A-frames secured by pre-cast concrete ballasts.
The Engineering Challenge
The client operates a logistics warehouse and required a rooftop solar array to offset grid power bills. The primary constraint was a strict no-penetration waterproofing mandate: anchoring structures by drilling expansion bolts into the concrete roof slab was prohibited.
Furthermore, the Trichy region is prone to seasonal high-wind storms, with wind velocities reaching up to 170 km/h. The structure had to be heavy enough to resist wind uplift forces without exceeding the roof slab’s maximum load-bearing limit of 50 kg/m².
Structural Design & Solution
The SOLBE design team developed a Non-Penetrative Ballasted Racking System built from heavy-duty Hot-Dip Galvanized Iron (GI) profiles (IS 2062 E250 steel):
NON-PENETRATIVE BALLASTED RCC PROFILE
[ PV Module Table ]
[ GI A-Frame Leg ]
[ Base Rail Profile ]
┌────────────────────────┐
│ Pre-cast Ballast Block │ <- M25 Grade concrete (45kg block weight)
└────────────────────────┘
══════════════════════════ <- EPDM Protection Pad (zero direct contact)
[ Flat RCC Roof Slab ]- Uplift Calculation: Under IS 875 wind calculations, the peak uplift force was calculated at $1.15\text{ kN}$ per base leg for corner modules.
- Ballast Weight Sizing: To resist this uplift with a 1.5x safety factor, we utilized pre-cast M25 concrete ballast blocks weighing $45\text{ kg}$ each. Base rails were isolated from the concrete roof using $6\text{mm}$ EPDM rubber pads to protect the waterproofing membrane from physical abrasion.
- Corrosion Protection: The structure was treated with post-fabrication hot-dip galvanizing (complying with IS 2629 / IS 4759 standards), providing a maintenance-free rust resistance lifespan of 25+ years in Trichy’s warm environment.
Key Performance Metrics
- Slab Load Pressure: Average structure dead load (including ballast blocks) measured at $18.5\text{ kg/m²}$, well within the roof’s 50 kg/m² capacity limit.
- Waterproofing: Zero leaks reported after two monsoon cycles.
- Tilt & Orientation: Panels were aligned to $11^\circ$ True South, achieving 100% of target yield expectations.
🚀 Partner with SOLBE Precision
Need assistance designing a non-penetrative solar array for an RCC concrete roof? Our engineering team in Trichy provides full ballast calculations and layout modeling.