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.

enter image description here

(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.

enter image description here

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?

  • Can't answer the structural question, but if you want to keep it, why not make it flush with the top edge of the ledgers to shed most of the water? And a few weep holes wouldn't hurt.
    – bib
    Jun 12, 2017 at 11:28
  • It is flush with the top of the beams, but since it's a 6 1/2" flat spot, it still holds water. I thought about weep holes, but I'm afraid the holes will cause the 2x4 to rot more quickly.
    – Tester101
    Jun 12, 2017 at 11:32
  • A bit of copper tubing hammered into the hole might help.
    – bib
    Jun 12, 2017 at 13:15
  • @bib Any problem using copper in contact with PT lumber?
    – Tester101
    Jun 12, 2017 at 13:19
  • Don't know. I know steel and galv is a problem.
    – bib
    Jun 12, 2017 at 15:27

1 Answer 1


I see no reason for that board, but a photo would help clear things up. I also assume that the joists are hung on the beam using standard steel hangers and approved fasteners. If all that is correct, you should be able to remove the board.

I'd guess that it was added to support decking joints that fell over the beam. Presumably the decking ran parallel to the beam. A better approach would have been to put individual blocks in that essentially carry the joist through the beam gap.

  • The beam members are simply nailed to the posts. The joists are attached to the beam members using nails (no hangers). This deck may have been built before hangers were required, or by an individual that didn't know hangers were required. The builder must have built the two sections of deck, by nailing the joists through the beam. Then they attached the beam of the two sections of deck to the posts, by nailing through the beams. Finally they inserted the 2x4 and nailed it in place.
    – Tester101
    Jun 12, 2017 at 13:51
  • Maybe I'll rip it out, and nail in some blocks as you suggest.
    – Tester101
    Jun 12, 2017 at 13:54
  • Thanks. FYI, there are no ledgers in this scenario. There are two beam members. Ledgers fasten to a wall. I'd just be sure that the joists are securely fastened so that the beam members can't twist away.
    – isherwood
    Jun 12, 2017 at 13:58
  • Only add blocks if your decking needs them, or if you think they'll keep your joist connections tight.
    – isherwood
    Jun 12, 2017 at 13:59
  • I was just using the word "ledger", because I wasn't sure what else to call them. I guess "beam member" is more accurate. I think the way the decking falls, I will have to add blocking.
    – Tester101
    Jun 12, 2017 at 14:03

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