Residential Deck Question 7

[zero1238]

I recently inspected a deck for a client where they had a rear deck off of the second story with a double ledger board attached over cedar shake siding. The IRC prohibits fastening a ledger to masonry veneer/stone or to a cantilevered flooring system but does not go over this issue. This just strikes me as poor building techniques and I would probably recommend that they add a beam beneath the joists and in front of the ledger to make the deck free-standing. You can even see the ledger being slightly rotated in the attached image, following the contour of the cladding. Would anyone disagree with this assessment?

 

[lexpatrie]

That seems very outside the intent of the code. How is the ledger attached anyway? Nails subject to withdrawal are forbidden, for example.

Free standing sounds fine but then you are adding cross bracing and digging ledge foundation at the face of the basement wall, etc. But that would he a viable approach, if you ask me.

Otherwise whatever attachment through the siding needs a tested value....

Post sizes, the beam above the post, and the stability of the post (and beam) would also be on the "to fix/normalize" list, and possibly the guard and the stairs.

Welcome to scope creep. Oh and the connection at the ends of the deck into the house for the 1,500 lb (right?) load.

 

[Eng16080]

I'm looking at that railing and wondering how that works! It doesn't look like there are any railing posts!

Anyway, back to your question: If you look at Table R507.9.1.3(1) in the IRC code, it only provides deck ledger connection spacings where the ledger is only up to 1" away from the rim board. So, I believe you're limited to only being up to this 1" distance from the rim board. In your case, with the double ledger plus all the siding and crap sandwiched between, you're well over that. I think somewhere else in the code explicitly states this limit, whereas the table only seems to allude to it. I suppose with an engineered solution you can perhaps exceed this limit, but I wouldn't want to mess with what you have here. Looks rather bad.

God, I hate decks!

 

[XR250]

Honestly, throw some 1/2"Ø thru bolts in every 8" O.C. and it will be fine. Might want to brace those posts though.
And the guardrail is sketchy AF as was previously mentioned.
Might be better to tear it down and start over.

 

[StrEng007]

Stabilize those posts with a knee-brace.

https://www.strongtie.com/fences_decksandfences/kbs_stabilizer/p/kbsz

 

[lexpatrie]

How does a knee brace assist the buckling of the post in-out of the... whatever. Perpendicular to the house. There.

 

[NorthCivil]

looks like a mildly dodgy deck to me.

probably wont collapse, but its not an "engineered" solution.

this is what i always tell clients in situations when im getting leaned on to sign something off that is generally distasteful.

"listen - its not so dangerous that i will call the city inspector to have this place condemned. but its not appropriately robust to call it an "engineered solution" "

 

[LittleInch]

What EXACTLY is the fixing between the ledger boards and the timber cladding??

I do like the way the deck rafters have been cut to allow for the slope of the beam hanger though...

That second photo makes it look like the posts are angled? Or is that a camera issue?

what have you actually been asked to do as that structure looks very poor, not "designed" and a decent bit of wind , too many guests and a bit of hidden rot and down she goes!

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[StrEng007]

lexpatrie,
Although you can't assume anything about the as-built design, I was suggesting the knee-brace as a way to stabilize any sway parallel to the house. It's a cheap add on that goes a long way.
I was not referring to column buckling.

 

[XR250]

Stabilize those posts with a knee-brace.

No builder in their right mind would use those Simpson contraptions.
They would run a 3/4"Ø lag bolt through the knee brace and into the slit between the two plies of the deck girder.
Much better way to go (being facetious obvs)

 

[lexpatrie]

Yeah the knee brace would do something along the parallel direction to the house in terms of wind load/required lateral/live load sway loads, but it won't do much for the axial strength of the post because the post can buckle in the other direction without being influenced by the joist and most deck posts are symmetrical. The lateral path isn't fantastic, but the current code would still call for the 1,500 lb connection into the structure at each end (or 4 750 lb connections into the structure) which likely aren't there, and the deck boards can potentially provide some sway resistance if those connections exist.

I'll link to the FAQ I created....

2009 - International Residential code adds "holdowns" at deck ends

 

[zero1238]

Thank you for all of the great replies. The ledger is currently connected with (2) 1/2" lag screws at 32" on center through all of that ledger garbage. I agree with the point about the knee braces. I do think this would be a candidate to tear down and start fresh though. There's not much about the current state of construction that I agree with and instead of trying to retrofit the entire thing, might be a better idea to start over. I'm just surprised there isn't more on this ledger situation in the code. On another note, I'm still fairly new to this site, how do I reply directly to people's posts?

 

[lexpatrie]

That's the thing, you don't. You can use the quote feature (person with a speech bubble over it, just left of the little gift icon on the "preview" and "submit post" line when you are responding, or you can just say it, or pretend this is twitter/discord and "at" people, but it doesn't do anything functional. Member to member communication isn't possible here, unless somebody has their email in their profile which is discouraged, but some people will include blue's clues to their email that's not *at least previously* machine-readable.

Also, this is the most current variant of this thread over in the Wood design and engineering forum. Do these deck beams look stable to you?.

Decks kind of merit their own mega thread that's trapped at the top of the Wood design forum, but the site doesn't have a feature like that.

 

[XR250]

@lexpatrie

I'm in NC, 2018 IRC. We do not have that provision.

 

[zero1238]

That really helps, thank you!

 

[lexpatrie]

You'd be on the hook, still, as providing lateral load resistance, it's just not codified. The random deck builder would be less obligated. I'd provide them anyway, you're an engineer you can "add" to the requirements if it's necessary for life-safety, despite what the lobbyists have done to the local code.

 

[XR250]

You'd be on the hook, still, as providing lateral load resistance, it's just not codified. The random deck builder would be less obligated. I'd provide them anyway, you're an engineer you can "add" to the requirements if it's necessary for life-safety, despite what the lobbyists have done to the local code.

mmm, I don't know about that. I'm only on the hook for standard practice, which is not providing this.
For taller or sketchier decks, I usually do spec a DTT1Z at each joist.
Back to the knee braces, do I x-brace every deck because I know these knee braces don't do shit?

 

[LittleInch]

" (2) 1/2" lag screws at 32" on center through all of that ledger garbage."

So how long?

Taken one out to see what actual length they used and what condition its in?

What are those screws actually embedded into?

that doesn't seem like a lot of fixing to me.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[lexpatrie]

XR you'd be better off looking at the planks as a diaphragm and providing the code required anchors at the ends (via a note making the deletion back in force), or demonstrating via your own analysis for some lateral load, whatever that is, and disclosing it on the drawings (I do that).

Its the along the house direction that's generally unstable, the other direction Is either bearing or tension in the required 1,500 Lb connections (outside NC, after 5 pm).

I don't have the language in front of me, but there's requirements for decks that are pretty broad. Like "design for all later loads" or "design for all loads" versus, say, "all code required loads".

 

[XR250]

@Lex

For decks that are not too tall, i usually just call out, "brace per code" For taller ones, I will X or V brace the posts full-height. if the customer doesn't like to see bracing, I will do under deck planar bracing that is tied into the house floor system.