A sandwich panel is a self-supporting element: it sits on the purlins and carries the snow, wind and maintenance loads itself. That capacity comes not from the name of the panel but from three things.
The three things that set capacity
Steel thickness. The two metal faces carry most of the load. The inner and outer sheets can differ in thickness; both are written separately on the quotation.
Rib geometry. On a roof panel the rib is a stiffener that increases the depth of the section. Three-rib, five-rib and seven-rib profiles cross progressively wider spans. Rib height matters too: on the five-rib TRIPAN and SOLAR profiles, for instance, the rib height is 37 mm.
The core as an adhesive. The composite action of the section is possible because the core holds the two sheets bonded together. Core density is therefore not only an insulation figure but a structural one: it is declared at 30-52 kg/m³ for polyurethane and 90-130 kg/m³ for rock wool.
Spans are not chosen by estimate
Purlin spacing is determined together with the snow load, the wind uplift, the panel thickness and the steel thickness. The load table is where those four variables meet, and the table is specific to the product. A span taken from a "similar product" table means a roof that deflects on site.
The load tables stand product by product in the Library section.
Wind uplift works differently from snow load
Snow load presses the panel down; wind uplift pulls it up and puts the load on the screw. Where uplift is decisive, what matters is therefore not the panel itself but the number and the layout of the fasteners.
On facilities in open country, on tall buildings and along the coast, that calculation is made separately. Fasteners and their selection are explained in the Library section.
Weight decides the structure
As the weight of the envelope falls, so do the purlin section and the steel tonnage. The difference between a polyurethane cored panel and a rock wool cored panel of the same thickness goes straight into the structural calculation.
How many kilos of envelope a project will carry is read from the panel weight calculator.
Four things that set the service life
The structural life of a panel depends less on the steel thickness than on the protection of the surface and the joints.
- Coating class: PVDF or plastisol instead of polyester on the coast and in aggressive atmospheres
- Pitch: minimum 7% on a sandwich roof panel; at a lower pitch, water sits at the joint detail
- Sealing of the joints: a joint left open is both a water and an insulation loss
- Annual maintenance: screw gaskets, gutter cleaning, tape and sealant checks
The maintenance and repair notes are in the Library section.
Most damage happens before installation
A crushed panel edge does not hold alignment and breaks the seal of the interlock. Stacking rules are therefore a technical matter: flat and firm ground, protection from moisture, a limited stack height, and lifting the panel with support at its centre. The unloading and lifting notes are in the Library section.