Is Your Deck in Good Condition?
Check and see if any boards are loose when you walk on them. Do they move, are any of them warped badly out of place and are they rotted? When you look at the wood of the deck, do you say "that wood is no good"? That is the easy-to-see problem and if the problem is that far you probably need to replace the whole deck.
There are harder to spot problems that you will be able to feel when you walk on the deck. If it feels at all spongy, if it gives at all when you walk on it, most likely the boards underneath that support are damaged in some way. You must realize that by the time that the dry rot gets so bad that you can see it on top, the whole deck will probably have to be replaced. You should get underneath and carefully look over all the underneath boards and see if you have any damage at all underneath. Take a screwdriver with you and poke it into the wood and see if it goes in easily anywhere.
Call me at (818) 548-8760 to get me to check out your deck and get you a free estimate on fixin' it for great outdoor entertaining. - Randy