I'm working on replacing the decking on an existing deck. While removing the old decking, I came across something I've not seen before. I've seen decks framed as illustrated below, where members are attached to posts to allow joists to be hung.
(This likely isn't a code approved method of building a deck anymore, but I'm not rebuilding the entire deck to fix it.)
The thing I don't understand, is that they added a 2x4 laid on its face between the two beams.
I'm not sure why they added the 2x4, maybe to stiffen up the "beam", or just as a nailing surface. Unfortunately, it works great at trapping water under the decking. All the decking that was in this area is rotten, and the whole area is damp (despite not having rain in about a week).
I've never seen a "beam" built in this way, and I'm a bit perplexed. Can I remove the 2x4, so that water is not being trapped? Is it there for some structural reason?