I can very much recommend Exel Composite's "system 30". It is a sort of lego-like system for building structure's frames, we've built several 30m by 10m barn/sh

I can very much recommend Exel Composite's "system 30". It is a sort of lego-like system for building structure's frames, we've built several 30m by 10m barn/shed type buildings with it that have withstood the elements for 20+ years. https://exelcomposites.com/wp-content/uploads/2020/06/EN_System-30-Data-Sheet.pdf https://exelcomposites.com/wp-content/uploads/2020/06/EN_Sys... junctions: https://www.etra.fi/en/engineering-plastics-e540/plastic-reinforcement-tubes-connectors-e5421/exel-system-30-e542105 https://www.etra.fi/en/engineering-plastics-e540/plastic-rei... tubes: https://www.etra.fi/en/exel-tubes-e54211505 https://www.etra.fi/en/exel-tubes-e54211505