A rooftop solar plant adds weight, changes how wind acts on a roof, and puts people and equipment on a structure that may never have been designed for either. The structural survey is where a responsible project starts. It is also where cut-price proposals most often cut corners.
What the survey should check
Purlins and rafters
Purlins carry the roof sheets and, once solar is installed, the mounting rails. The survey should record purlin section, spacing, span and condition, and check capacity against the additional dead load of modules and mounting, typically in the range of 12–15 kg per square metre, plus maintenance live loads.
Roof sheets
Sheet gauge, profile and fixing condition decide which clamps can be used and whether the sheet itself can carry point loads. Thin or heavily corroded sheets may need replacement before installation, which is far cheaper to do before modules are in the way.
Corrosion and water ingress
Rust at fixings, gutters and ridge caps is common on older sheds, especially near the coast. The survey should map it, because every penetration and clamp added later is a potential leak path if the underlying steel is compromised.
Wind uplift
Bangladesh's cyclone exposure means wind load, not weight, is often the governing design case. Edge and corner zones of the roof see much higher uplift than the centre. Layout, clamp spacing and module orientation should all follow from a proper wind-load calculation.
Access, safety and the route for cables
A roof that can carry modules still has to be safe to work on for 25 years. The survey should identify fragile skylights, fall-protection anchor points, ladder and hoist access, and where walkways are needed so cleaning crews never step on modules. It should also trace a practical route for DC cables and locate inverters where they are shaded, ventilated and reachable, because an inverter installed in a hot, inaccessible corner will cost yield and maintenance time for the life of the plant.
What happens when the roof falls short
A survey that finds problems is not a failed project. It usually leads to one of three outcomes: local strengthening of purlins, sheet replacement in affected bays, or a revised layout that keeps modules off weaker zones. Each is a known cost that can be priced into the proposal, rather than an unknown one discovered after a storm.
Every system we design through our EPC service starts with a structural survey signed off by a qualified engineer. If a proposal you have received does not mention one, ask why.
Written by
Engineering Desk
Design & EPC team, Emerged Power
Our design engineers write about the details that decide whether a plant hits its yield — from purlin spacing to string sizing.