IRC section R502.2.2.3 1

The NC code specifically deleted that part. What does it say?

I agree it seams a little extreme. It was implemented a couple years back I believe (2009?). I haven't had any complaints from contractors yet about the ties going back into floor systems or into concrete walls yet. It appears it is used to address decks pulling off ledgers. But, you also need to watch your attachments at the deck beams as well and it isn't really addressed. If you are hanging your joists off the beams and don't have a tie from the joist to beam, you are essentially creating a connection at the beam that the code is attempting to correct at the ledger of the house. So it appears there are still holes in the prescriptive method depending on the framing technique used.

AWC's prescriptive guide:

I'm questioning in my other post the need for the requirement of knee braces as well.

I have addressed the joist to beam connection with a Simpson HRS6 in the past.

Sorry for the multiple posts, just thinking of things I forgot to mention as they come.

slta

R502.2.2 Decks. Where supported by attachment to an exterior wall, decks shall be positively anchored to the primary structure and designed for both vertical and lateral loads as applicable. Such attachment shall not be accomplished by the use of toenails or nails subjected to withdrawal. Where positive connection to the primary building structure cannot be verified during inspection, decks shall be self-supporting. For decks with cantilevered framing members, shall be designed and constructed to resist uplift resulting from the full live load specified in Table R301.5 acting on the cantilevered portion of the deck

R502.2.2.3 Deck lateral load connection. The lateral load connection required by Section R502.2.2 shall be permitted to be in accordance with Figure R502.2.2.3. Hold-down tension devices shall be installed in not less that two locations per dick, and each device shall have an allowable stress design capacity of not less than 1500 pounds.

You can see some of the proposed attachments here:

Huh. NC doesn't require any of that extra lateral stuff - interesting because we do get hit with hurricanes on the east coast. It will be interesting to see if that shifts.

That AF&PA Deck Construction Guide #6 is a very good guide for the intent and thought process of designing and building a good, structurally sound, deck. I think the 1500lbs. is something of an arbitrary number, picked by committee, to force fly-by-night deck builders to do something in the way of tying the deck to the building in a meaningful way. Doesn’t the same code section wave this criteria if the deck’s connection and stability is checked by a real Structural Engineer? Obviously, someone has to check the deck for stability, if we care. Remember, a lot of DIY’ers and deck builders thought it was perfectly o.k. to attach a ledger over vinyl siding, foam insulation and sheathing with 3 or 3.5" gun nails, and a few 4" lag screws. After all, the deck did hang there after they were done building it.

The LL for decks should be at least as great as those LL for the interior spaces they are accessed from. That is, a residence 40lbs./sq.ft., a bar, frat. house or restaurant something more. But, should we sum that with snow and drifting or roof slide snows too? The lateral loads are not very well defined for decks, we know about wind and EQ. Without privacy walls and the like wind is usually manageable. Make some account of the total face areas of the framing members to the wind, and potential uplift. It is a fairly light structure, but all the mass is concentrated at the deck level, and the whole structure is on 3 or 4 tooth picks out at the outer edge. The biggest unknown is the people loadings, and most deck failures have involved these. The extremes, of course, are four or five drunk football linemen swaying in unison to some music, out at the handrail, to impress the cheerleaders; or a group of people rushing to the handrail to see a deer in the back yard. What are these loadings, not particularly easily defined? Pay attention to the orientation of the deck. A 20' long deck on a ledger, and projecting out 8-10' from the bldg. should not be much of a problem. But, the same deck connected to an 8' ledger and projecting out 20' from the bldg. is quite a different animal. Is the deck connected to the bldg. of several sides and protected by the bldg.

On new construction an intended deck attachment is easily accommodated, with some extra blocking, and proper floor sheathing nailing, etc. On an existing bldg. it is more difficult because you don’t know how the floor sheathing was nailed to the rim joist, or the joists for that matter, and you are unsure of how to get that lateral load back into the floor diaphragm. The ledger should really be fixed directly to the rim joist, maybe through the sheathing, but not through added layers of material, where the fasteners end up cantilevering to far. That pocket should be flashed up behind the drainage plane, and include end dams, all draining out under the ledger. Then there should be a second flashing installed over the ledger and behind the drainage plane. Finally the ledger is fixed to the rim joist, and some size and spacing proposals have really complicated that process. These prescriptive requirements are almost always needed to keep idiots from killing other people. When the decking is parallel to the bldg., I fix the last piece of decking under the threshold on precut wedges, atop the joists, to make that deck piece drain away from the bldg. and the ledger. Also, flash the tops of joists and built-up beams with peel-n-stick or some such to keep water from accumulating and siting at these locations, they never dry out.

I just addressed the lateral occupancy load in another post. One recommendation is to use 8-10psf lateral load generated to occupancy on decks. so the 1500# may be overkill or under-designed depending the size of the deck, configuration and how the deck is braced and supported otherwise. Complete load path...
In a typical rectangle attached deck cantilevered diaphragm-like with no other brace mechanism I would say this is reasonable if not unconservative.

I agree with dhengr on construction. Constructable: yes. Existing construction constructable: difficult but doable. If you don't want to do this then build a freestanding deck and all the bracing that goes with it.


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