During my 20 years in the building business I've replaced a lot of rotted decks and porches. Some of these were less than ten years old; a few were less than seven. Many of the homes in question were otherwise well-built, with solid framing and quality interior trim. But the builders failed to provide two key elements: good watershedding details and air spaces to allow the porch lumber to dry after it got soaked by rain or snow. The secret to a long-lasting deck or porch lies in keeping water out of the joints between the various layers of lumber and ensuring that those joints can dry out if water does get between them. Here are some simple techniques