Protecting your new cedar or pressure treated (PT) woodwork from the elements will significantly extend its longevity.
This can be achieved by applying a sealant that penetrates and coats the wood. Oil based sealants are recommended over water based sealants. They easily penetrate the wood deep into the grain and have a higher resistance to the elements. Oil based sealants maintain a more even finish and require less maintenance.
Sealants should be applied at least a month after the fence or deck is constructed in order to allow for the internal moisture to escape & pressure treating chemical to air out. When applying sealants, ensure the wood is completely dry & make sure to follow the manufacturer instructions as product specifications may vary.