It may seem obvious that outdoor furniture should stand up to the weather. After all, you don’t want the hard job of carrying it out and back in every time it is to be used. And unless it can stay outside all the time, you will end up not wanting to use it at all because the job is so onerous. If the furniture is to be located on a grassy area it is even more important that it is weatherproof.
When something heavy is left on grass it will sink in and reach the soil underneath, which is often quite damp. This will rot the legs of most timber furniture, because even if it is painted, that constant wear on the base of the legs will soon penetrate the paint and the moisture will seep up into the inside of the wood. The end result will be the paint is compromised and the timber will rot from the ground up.
At least, this is what happens with softwoods, especially anything left untreated. However, certain hardwood decking will stay strong and in their natural state for many years even though they are outside in the weather. Think of all those heavy beams used for piers or boat masts. They get wet all the time, but they last for many years. Boat wood furniture is therefore ideal for any external design or renovation that needs furniture.