Support posts set in concrete footings and part of railing
by Concerned about twisting railing posts
I have a 25 year old pressure treated pine deck that is holding up pretty well. It is a raised deck approximately 4 feet off the ground. It is sitting on 4x4 support posts that go five feet underground into concrete forms.
My problem is that these posts come straight up and also act as the deck post railings. Over time some of these posts have twisted since I live in a four season climate where the ground freezes in the winter and thaws in the spring.
Is there anyway of fixing the twists?
The beams are bolted into the side of the deck and I can see that some of the post nails are twisting and separating from the deck. I have never seen another deck where the piers come straight up to act as posts except for porches or covered decks.
Decks with support posts set into concrete forms which function as frost footings are very uncommon these days and for many reasons. The posts should be treated for ground contact because they will be perennially moist inside the concrete which wicks water.
It is even more uncommon to extend the posts vertically so that they act as the deck railing posts. Worse still, as you seem to be describing, is that the deck itself is supported against the side of these posts by metal fasteners, perhaps bolts or worse... nails. If so this is a big big no no. The deck must be supported by a carrier beam which in turn is supported by the posts on some kind of load bearing footing system.
No Quick Fix For Twisted Posts
I hate to tell you but those railing posts that are twisting cannot be untwisted. You will have to cut them off and I would recommend replacing the railing with a surface mounted wood or aluminum/metal railing.
You should try to cut the post off below the level of the decking and this will be tricky but not impossible. Then you can simply replace the one decking board that has been effected.
The Support For Your Deck
More importantly, now is the time to address that bizarre system where your deck is merely attached to the support posts by horizontal fasteners.
At the very least the posts need to be cut down to allow a proper carrier beam (at least 2-2x8s laminated) to sit on top of the posts securely and then attach to the underside of your deck framing.
For all of you reading this, and if you are at the planning stage of designing and building your deck, do not use support posts set into concrete forms and also use them for the railing posts on the deck.