Deck posts centered on footing vs plumb
JCARTER93
| Posted in General Discussion on
Hi Guys, I’m new here.
I’m building a deck and have a small (I think) issue. I have a 24×10 deck planned with a ledger and 5 footings. The footings will be 12-diameter concreter pylons 42″ deep poured directly into holes sheathed with concrete tube forms. Pylon holes 1,2, and 5 are at 9’6″ from the ledger and pylon holes 3 and 4 are 9’8″ from the ledger.
I am planning on pouring the concrete today. So I can mount every post (4×4) at the center of the pylon and be out of plumb to the beam by 1/2″ OR I can mount each post 1″ off center of the pylon and have them plumb under the post. The posts will be approximately 39″ long under the beam.
My intuition is to mount the posts off center, which option would you all recommend?
Replies
Plumb
Thanks. Do I have any reason to be concerned about the off centeredness?
I built a 24x24’ shed/chicken/peacock building on 10” sonotubes. Not every 10” tamarack log post was centered on the pins on the sonotubes, which are carrying the full weight of walls and roof (and floor on half of it). The only issue is if you have a building code, and if you do their concern is not about whether the posts are centered on the sonotubes, but how far off-center they are from the footings.
Always plumb. As for centered-ness, that should always be the goal, but if you're a little off it won't be a problem. You get into trouble if you miss badly and the post is hanging off the edge, or the anchor bolts that you're attaching your post base with are close enough to the edge to shear off a piece of the pier footing when you drill. Sounds like you're in good shape. Rest easy.
The anchors are cast in place and the post won't hang off the edge. I've installed the post footers and it looks like it'll work. I'm still kicking myself for the off centeredness just for ascetics.
From a practical structural engineer:
1% out of plumb is not necessarily critical (e.g. about 1" in 8 feet). Given that the deck is anchored to the house at the ledger, if the top of the posts are leaning slightly TOWARD the house, I wouldn't lose too much sleep over it.
That said, having 2 of the 5 posts out of plumb is likely to be apparent to a reasonably astute observer.
Most metal post stand-offs/bases have a attachment hole much larger than the anchor bolt so you'll have some play there. I'd try to get them all as close as possible to a straight line between post 1 and 5 and call it a day.
If this were a free-standing deck NOT attached to the house my response would be different, particularly if you're in a seismically active area.
Mounting each post at the center of the pylon might result in being slightly out of plumb by 1/2" to the beam. While this might not seem like a significant difference, it could affect the overall appearance and stability of your deck.
On the other hand, if you mount each post 1" off center of the pylon, you can ensure that they are plumb under the beam. This alignment can enhance the structural integrity of your deck and provide a more visually appealing result.
Considering the approximate length of the posts under the beam (39"), it seems reasonable to prioritize their plumb alignment to maintain stability. Additionally, having the posts centered on the pylons could potentially make them more vulnerable to lateral forces.
Therefore, based on these factors, my recommendation would be to mount each post 1" off center of the pylon to achieve plumb alignment and enhance the overall stability of your deck.