Standards Library · 06
BS EN 1991-1-1
Densities, self-weight and imposed loads
The Eurocode covering densities, self-weight and imposed loads for buildings. On a rooftop PV project its quiet contribution is access and maintenance loading.
What it is
BS EN 1991-1-1 provides the densities and self-weights of construction materials and stored materials, and the imposed loads to be applied to floors and roofs by use category.
For an existing roof it supplies both halves of the starting point: what the structure already weighs, and what it is required to carry in use.
Why it matters for rooftop solar
A roof with an array on it gets visited more often than it did. Cleaning, inspection, electrical maintenance and panel replacement all put people and equipment on a surface that may have seen a roofer once a decade.
The array's own dead load must be stated with its build-up rather than as a single number. Modules, mounting system and ballast are separate contributions, and lumping them together hides where the weight actually sits.
Existing loads beyond the original design intent belong here too: services, plant, ductwork, walkways, safety systems, and previous overlays or re-covering.