how to install aluminum railing on composite deck

Composite decks require careful installation to prevent moisture entrapment and deck board deformation. Begin by installing composite-deck-rated mounting blocks—a flashing kit—beneath each railing post location. Fasten the plastic mounting block to the joist with structural screws, ensuring it sits flush and level with the deck surface. Position the aluminum post over the block and secure it with the provided lag screws or through-bolt kit. The mounting block includes a built-in flashing flange that directs water away, maintaining deck integrity. Assemble rails, infill, and caps per Archsky’s standard railing guide. Finish by sealing around post bases with a compatible sealant to prevent moisture ingress. This system preserves warranty compliance for composite decking manufacturers and ensures a robust railing attachment.