Thanks for the info! I recently bounght a house in VA and ALL of the decks and exterior woods on all of the houses I looked at (including the one I bought) are bare wood and looked like they were never sealed. I looked at some high priced places and the big decks on the larger, more expensive houses look the same as the smaller cheaper ones. The seasons here are extreme and I can’t figure out why no one takes care of their decks!
Unfortunately, wood shrinks and swells with changes in relative humidity. When it dries out, it tends to crack and split apart. Southern Yellow Pine, which is what is most likely on your deck, tends to do this more so than other species. However, it is the least expensive decking option in your market. That is why it is so prevalent.
This is why composite decking products have gained so much market share in the last 10 years. They have their issues too. In heavy humidity areas like Oregon or Washington they tend to have mold growth problems. There have also been dozens of new manufacturers of composite decking that have come and gone out of business in the last ten years. Many of them made inferior products. Then companies came out with 100% PVC decking. There are about six major manufactures of PVC trim boards. AZEK being the most widely distributed. The problem with PVC is it is very expensive and it also shrinks and swells in length. Therefore, it can buckle if boards are butted to tight. So, finally the decking companies came out with a product that has a composite core and a PVC exterior shell. This is the best product currently on the market and why I suggested it in my earlier reply. This type of decking has virtually no maintenance, is dimensionally stabile and will not rot or mold. Also, the producers have a system to attach their decking to the joists below without the screws showing on the face.