About the Roof Load Check
A roof-load check verifies that the structure can safely carry the extra dead load of the solar array (modules, mounting structure, and any ballast) plus the wind and live loads it induces, before installation. It compares the added load per square metre against the roof type's allowable capacity.
Formula
Added dead load (kg/m²) = Array weight (kg) ÷ Array footprint (m²)
- Array weight
- Modules + mounting structure + ballast (kg)
- Array footprint
- Plan area the array covers (m²)
How to calculate it
- 1Estimate the array's total weight: module weight (~12–13 kg each) plus mounting structure and any ballast for non-penetrating flat-roof mounts.
- 2Divide by the plan area to get the added dead load in kg/m².
- 3Add the code wind uplift and live loads per IS 875.
- 4Compare the combined demand to the roof's allowable capacity — RCC slabs have ample margin; sheet/PEB and older timber roofs need a purlin/rafter check.
Worked example
A flush RCC rooftop system typically adds only ~15–25 kg/m² of dead load — comfortably within a designed RCC slab's capacity. A ballasted flat-roof mount can add more and must be checked; a light sheet-metal or asbestos roof usually needs structural reinforcement first.
What you can calculate
- RCC / PEB / Timber
- kN/m² check
- System load
- Pass/Fail
Standards & references
Frequently asked questions
How much weight does rooftop solar add?
A flush-mounted rooftop system adds roughly 15–25 kg/m² — light relative to a designed RCC roof. Ballasted mounts on flat roofs add more (the ballast resists wind uplift), so those always warrant a structural check.
Can any roof support solar panels?
RCC roofs almost always can. Pre-engineered/sheet-metal roofs depend on purlin spacing and gauge. Old asbestos, fragile, or corroded roofs often cannot and need reinforcement or replacement first. A quick structural assessment per IS 875 settles it before installation.
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