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The 4x4 posts for the railings on my deck are attached to the surface (2x6 boards) using plastic post anchors with lag screws rather than going through the surface and attaching to the joists. The ends that attach near the house and by the stair railings feel fine, but towards the center (about a 20' long deck) it's a bit wobbly. Posts are roughly 4-5' apart. Is there a way I can reinforce these posts without replacing them with longer ones and attaching them underneath the deck like it should have been?

Don't have any pics of the deck on hand (I'm at work), but these are the anchors attaching the railing posts onto the deck.

Deck is built on a significant slope and ranges from 2' off the ground to about 6'.

enter image description here

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  • Good fixes are very dependent on the details of your situation. Post photos when you can, please. Show the outside of the post base area as well as an overview of the entire railing run.
    – isherwood
    Jun 30 at 14:57
  • How high up is the deck? This could be a dangerous situation.
    – JimmyJames
    Jun 30 at 15:17
  • Solutions don't belong in your question. Feel free to post and accept an answer, or accept the best alternative answer.
    – isherwood
    Jun 30 at 19:01
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Suggest replacing the existing post base connectors with this one, which is made from steel, and considerably much stiffer than what you have now.

enter image description here enter image description here

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  • I like those but unfortunately I don't think they'll work for me. Description shows they have a height of 5.6", this will get in the way of the bottom rail which sits as just under 4" from the surface. I think the 4" height is a code thing, but regardless I'd either have to drill through the metal and reattach each railing, or shift them all up about 2".
    – Phaelax z
    Jun 29 at 15:52
  • 3
    The problem is that the current weakness is a combination of (a) attachment method (which you already said you don't want to change), (b) plastic vs. steel (stiffness of connector) and (c) height of connector. Jun 29 at 15:56
  • I think you can place a 4 x 4 x 1 1/2" spacer in the bracket to raise the post and the bottom rail if the nails can get to the post. It is still a better alternative than the original. Provides the large bolt on the base can penetrate the deck and be fastened from below.
    – r13
    Jun 29 at 16:05
  • 3
    Another idea is to add a short diagonal to the post to stiffen it. It can be annoying though.
    – r13
    Jun 29 at 16:10
  • 1
    The bottom rail has to be within 4" of the deck to meet modern code. Also, your additional ideas should be in your answer, not down here.
    – isherwood
    Jun 30 at 14:57
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Diagonals connecting the posts can mitigate racking risk.

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  • And the diagonals might be wire, and much less visible than wood. Jun 29 at 18:16
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    While the title mentioned "racking", the problem described is clearly not that. It's simple lateral wobble. Diagonals parallel to the railing won't help.
    – isherwood
    Jun 30 at 14:59
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A diagonal brace from corner to corner would be ideal.

If that interferes with your in-fill panel, then two smaller braces in the corners would work adequately. Simple 50x50 / 2" square outdoor-treated timber would would be sufficient, and brace can be recessed from the edges enough to make it harder to see.

enter image description here
image is for deck supports, not a railing. You can probably get away with smaller braces than 1/3.

Downside, its another surface to catch dirt, and will need paint/stain/protection. You'll also need to do accurate mitre cuts.

Ultimately, you're working to compensate for a poor initial design. Whoever designed this needs to stop doing it like that, and run the railing support down through the deck and into something more solid.

Your image shows a concrete pad, with bolts. In that instance, there's no good way to embed a post into concrete after the fact, so its the best of some bad options. That someone has used the same footer on wood means they didn't think it through.

And PLASTIC ?? That product really should be powder-coated steel. Cheap plastic is unsuitable as a structural component of anything.

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  • 1
    Maybe I didn't explain it well enough or I misused the word racking. Think of somebody leaning against the railings, that's my concern. At the end of the day, I decided to just cut holes in the deck and drop new posts down to where I can attach them to the joists. I looked underneath and I think I should have the room at the posts current placements without anything interfering. More money, more work, but ultimately I think it'll give the best result.
    – Phaelax z
    Jun 30 at 5:47
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    "Cheap plastic is unsuitable as a structural component of anything." The product description says they are for this purpose. That seems totally crazy to me as well but I'd interested to hear why the manufacturer thinks this an appropriate use.
    – JimmyJames
    Jun 30 at 16:21
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    @JimmyJames et al, a common misunderstanding is that these are intended to hold up a post--they're not. They're to hold a post in position with respect to the mounting surface only, and the top of the post would be anchored by other means. You've made a faulty assumption vis-a-vis the description, which simply includes general use cases.
    – isherwood
    Jun 30 at 18:50
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    @isherwood OK, I can accept that but I don't see why I would be the only person who might make that assumption based on said description. In fact, I could imagine that has something to do with how the OP ended up with these used that way.
    – JimmyJames
    Jun 30 at 18:54
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    Fair, but there are a great many things in construction which folks use incorrectly, up to and including the lowly 2x4. (I've seen some astoundingly flawed garage shelves.) Retailers can't be responsible for that. It doesn't take a whole lot of practical experience to learn that this just won't work.
    – isherwood
    Jun 30 at 18:56
3

Can you avoid replacing your newel posts?

Probably not, but...

As you've implied, the right fix is to plunge the posts through the decking and mount them securely to the framing. It's understandable that you don't want to do that now, but it's probably worth doing. Heavy duty post bases are fugly and probably too tall, and they still won't give you a truly solid feel. There's just too much torque on them when dealing with softwood.

The good news is that you may not need to do them all. If your top railings run through, or if you're willing to add a stiffener (say in the form of a flower planter), you could get away with doing just one or two on each long run between corners, where stability is somewhat inherent.

4
  • Looking at the link for these post holders it says: "used to Surface mount 4 x 4 wooden posts on a deck or concrete for railing" but I can't see how these would ever be adequate from a safety perspective. This can't possibly be up to code, right? I feel like this has lawsuit written all over it.
    – JimmyJames
    Jun 30 at 15:47
  • Safety doesn't depend on absolute rigidity, which is more of an aesthetic thing. It's all about load handling, which is why cable and chain railings are legal. You're right, though--I wouldn't have expected it to pass an inspection.
    – isherwood
    Jun 30 at 15:48
  • I just can't image one of my large mammal friends falling over into a railing and these bases holding. I would expect either the base to crack around the screws. Cables have tensile strength which make a lot of sense (superior even) for holding things back. Maybe they are more sturdy than they look but they don't seem fit for this purpose.
    – JimmyJames
    Jun 30 at 16:17
  • The deck did not pass my VA inspection and as a result my home owner insurance actually said they wouldn't renew the policy unless it was addressed. I had just bought the place over winter.
    – Phaelax z
    Jun 30 at 18:31
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If you've already decided that this is how the railing will be mounted and you just want to make it less wobbly, add braces similar to this:

enter image description here

(Drawing by Regal Rail Braces)

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  • This could work if there's enough of an offset to the deck rim, or if there's willingness to block out the brace mounts.
    – isherwood
    Jun 30 at 18:48
  • Whoa there! You can't accuse me of distaste and then suggest blocking out the brace mounts! :)
    – jay613
    Jul 2 at 12:26
  • A tasteful way to do this would be to have braces curving organically out from under the deck where they are cantilevered on the joists. But for all that effort it would be easier to just mount the posts on the joists properly.
    – jay613
    Jul 2 at 12:40
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One idea, not sure how great it is but it fits in with your constraints. It might not be possible for every post either.

The basic idea is to drive lag bolts (screws) from the underside of the deck and pull the posts down tight against the top of the deck. You'd want fairly large screws (I was able to find 17" lag screws once) and you would want to be sure you drill a properly sized hole to prevent splitting the post but not so large that the threads don't hold firm. I think you'd want at least two screws per post arranged perpendicularly to the direction of concern (outward, I take it.)

Holes drilled through the deck and post holders (if necessary) should be larger than the outer diameter of the threads. You want the screws to pass through freely.

The post holders should stay as noted in the comments. That would help prevent small movements from deforming the deck or the posts.

Underneath, you would need some sort of plate. Otherwise, the screws heads will tear through over time or catastrophically.

The key here is to pull the posts down tight so that the force from leaning on the railing is transferred to the plate and spread out to the bottom of the deck surface. One hitch is that if you do a really good job at this, you might destroy the plastic base.

UPDATE: Alternately you could purchase something like this:

enter image description here

These are designed for concrete but you could put blocking underneath the decking (attached to the joists) and secure them to that. You'd want to orient it so that the 'wings' on top are parallel to the railing.

It's basically the same idea with a couple (possibly crucial) differences:

  • It's simpler IMO, no drilling holes into end grain.
  • The decking material now is no longer involved in any part of the structure of the post.

I think this is a lot better than my original suggestion. A lot less work, maybe less costly (?), and far more secure. You might want to spray paint them with an appropriate product for better aesthetics.

Not sure this is optimal but I think it's better that what you have now. Also, after you price the hardware, it might not be worth it compared to getting longer posts. And honestly, isherwood's answer is the right way. If this deck is more than a few feet above the ground, I would definitely suck it up and fix it properly and if it's not, there's still risk of injury.

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  • It's not a bad idea, possibly the only idea without changing the existing structure. But it looks like we're all in agreement on this one, just suck it up and do the extra work. So that's what I'll do. (sometimes I just need folks to tell me what I already know)
    – Phaelax z
    Jun 30 at 18:45
  • @Phaelaxz I just saw your comment on the insurance inspection. I would make sure whatever solution you go with is going to pass muster with them before you do it.
    – JimmyJames
    Jun 30 at 19:17
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    The threaded concrete post base is yet another piece of hardware that is not intended to hold up a post. It's intended to locate the post, and isolate it from the concrete, but it'll fall right over if you try to use it to hold up a post that's subject to lateral forces. It's essentially no different from the plastic one for our purposes.
    – isherwood
    Jun 30 at 19:46
  • @isherwood I get what you are saying but you'd have to either break off threaded bolt off (maybe that's the weak point) or snap the through-bolt somehow (and up to eight other screws, if used), break the blocking, or somehow snap off the 'wings' that hold it to the post. Not saying it's impossible. I've pushed over posts set in concrete. If we are talking about those kinds of forces, who says the fasters into joists won't snap?
    – JimmyJames
    Jun 30 at 20:00
  • The connection to the post is too short and flexible to add stability (remember--softwood). It's not really about the bolt. Trust me on this one. You could walk up and push it over.
    – isherwood
    Jun 30 at 20:01

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