Pressure treated lumber is made from southern yellow pine. Due to extreme harvesting pressure, the average age of each tree before harvest is dropping and as a result, so is the grain density. Additionally, preservatives now used are inferior to those used in the past. Production demand also means rushed production, meaning boards often arrive at a job site soaking wet. Because lumber is made from living organisms, each board is inherently different. So aside from the longevity concerns, the quality concern is also utterly inadequate. Even when crowned, planed, sorted, and taped, the boards will still shrink and expand asymmetrically and yield a deck surface that looks like the waves of an ocean. If you are putting a high quality deck board on top of a frame that will be in constant motion and rot decades before the deck boards have lived out their life, you have functionally nullified a large percentage of the money you spent on the boards, creating a significant net loss. We do not offer pressure treated lumber because we believe in delivering value and quality to our clients. Pressure treated framing offers neither, modern framing delivers both in abundance.