Redwood logs are usually cut to maximize the longer length lumber, ( up to 20’ in length). Most decks are built with the underpinning ( joists or girders) on 16” centers. This maximizes the use of 4’ multiples in the lumber. If we could produce all 4’ multiples, we definitely would!! However, because of defects, trimbacks are necessary. This leaves 10’ and 14’ which do not fit the normal 16” center without unnecassry waste. If you can configure your deck so that many of the areas will take one of these lengths, often times you can save money by offering your local lumber company to use these lengths they must buy , but have a harder time selling. The yards will often times lower the cost on these lengths to move them out. You save money, they sell hard to move lumber , and a win-win exists for all.