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I have a bridge in my backyard that spans a mid-size creek. Currently, there are posts reaching only ~18"-24" above the ground. I would like to add a railing to the bridge.
To attach a railing, can I extend the height of the posts by attaching 4x4s to the existing posts, and if so, what's the safest/sturdiest way to do this?
If not, what are some other options?
![Bridge][1]](https://i.stack.imgur.com/DVtRY.jpg)
The question is rather open-ended. Here are my ideas in order of personal preference:
Replace the posts with taller ones. There are only four, and this would yield the cleanest appearance and extend the life of the bridge. Judging (from a distance) by the disintegrating center of the near left post they're on their way out already.
Go with a baluster-supported approach. By adding balusters at close intervals attached to the bridge beams you eliminate the need to rely on the posts altogether. You may need to add cross-bracing (boxing) between the beams to reduce twist.
Extend the posts with scabs or gusset plates. These could be 2x4s bolted to two opposing sides with substantial lap, or metal bars or sleeves.
Sister post extensions to the sides of the existing posts. They'd need to lap at least 1/3 the railing post height, so they may need to extend into the soil somewhat.
Consider capping or sloping the post tops to help reduce moisture accumulation and rot.
