Teak and iroko are trade names, not scientific ones, and durability class EN 350 gives a standardised way to compare species that trade names alone do not.
Trade name versus scientific name
Teak sold commercially is almost always Tectona grandis, but iroko, sold under one consistent trade name, can come from more than one closely related species depending on the supplier and region, which means two shipments labelled iroko are not always botanically identical.
For a specification that needs to be precise, referencing the scientific name alongside the trade name removes this ambiguity, particularly relevant when sourcing from a new supplier for the first time.
What EN 350 durability class actually measures
EN 350 rates timber's natural resistance to decay on a scale from class 1, very durable, to class 5, not durable, based on standardised laboratory and field testing rather than reputation or trade convention. Teak typically rates class 1 to 2; many commodity softwoods rate class 4 to 5 without treatment.
This scale is what allows a genuine comparison between species being considered for the same application, rather than relying on which name sounds more premium.
Applying this on a yacht specification
Specifying both the scientific name and the EN 350 class for exterior joinery timber, rather than the trade name alone, is what lets a yacht owner or captain compare quotes from different suppliers on genuinely equal terms.