Standards Library · 05
BS EN 1990
Basis of structural design
The head Eurocode. It does not describe any one load; it sets out how loads are combined, and with what partial factors, to arrive at a design case.
What it is
BS EN 1990 establishes the basis of structural design: limit states, combinations of actions, and the partial factors applied to each.
It is the standard that turns a list of individual loads — self weight, imposed, wind, snow — into the combinations a structure actually has to be checked against.
Why it matters for rooftop solar
An array is never assessed in isolation. It is assessed in combination with the actions the roof already carries: its own weight, services and plant, access loading, wind and snow.
This is where an assessment most often goes wrong quietly. Checking the array's dead load against a spare capacity figure is not the same as running the combinations, and it can pass a roof that the combinations would fail.
It is also why an assessment is valid only for the array it assessed. Change the layout, the module or the mounting system and the combinations change with it.