I will bet anyone a steak dinner that an architect “designed” this. It looks like the two ‘squares’ are about 10.5’x10.5’ each. The roof looks like it’s fully supported by the posts.
But when you calculate this out, it barely works for a triple 2x12 center girder, and even though deflection is ok, it’s close to failing for moment. That is the hallmark of an architect doing this kind of sizing: they never look at moment or bearing, just deflection. And the only way you get that result is by looking up a product table, and not doing the calculations.
As I tell my clients, “10 different inspectors can look at this, and expect 10 different answers. But this is my opinion…”
Besides the other “issues” with the deck fastening, can anyone point me where parallel joist ARE NOT allowed( as per the OP’s original question)? If so, I will put it in my narratives and inform my clients going forward.
The deck joists can be perpendicular, parallel or at an angle. Just calculate the deck loads and follow the load path to the ground. Each member should be checked for bending, shear and compression. From my experience the weak link will likely be at a connection or inadequate footing.
What you have are load bearing beams running perpendicular to the wall. Are those beams bearing on the foundation, not connected to the ledger with joist hanger? Are the beams bearing properly on the exterior posts? In one of your images, the beam is resting on a 2 x 2 ledger strip, a structural defect. In another it appears it may be bearing on the foundation, at least it penetrates the brick facing. Another, the beam appears to bear on part of a 6 x 6 post, which is fine if the bearing square inches is enough and it’s secured against lateral movement.
In lieu of joist hangers, the joists are fastened to the above beams with 2 x 2 ledger strips. Not the best, but acceptable. They need minimum of 3 nails supporting each joist, an important component.
I wouldn’t say “it’s all wrong”. Ironically, on Monday I inspected a home that had at least 12 sides to it, in essence round. It had a deck surrounding half the home, framed like yours, with load bearing beams perpendicular to the house walls and joists parallel to each facet of the home. Ledger strips were used under the joists, because angled joist hangers meeting the needs of the deck framing were not manufactured. It’s legit, if done correctly.
I wanted to let everyone here know that I am in the process of working with InterNACHI to update the deck inspection class to address issues like this that come up during inspections.
The updated class will incorporate many of the items from the DCA6 and other updated deck construction guides and newer code practices. The class was last updated in 2009 so we are doing a revision. The class will be taught over Zoom for credits for MD inspectors and some other states as well. NACHI will have the full list of credited states after the revision is complete.
Once I’m finished with the revision and any edits from NACHI we will put out a post so that everyone who wants to take it can get some CEUs along with the updated info. I’m about 80% down now, so shouldn’t be too much longer.
If there are specific things you guys have questions about or want to see included in the new class, send me a message.
I personally don’t think that there is anything wrong with the deck joist running parallel to the house . My issue is with the deck supporting girders coming out from the house that are attached to a ledger board with no joist hangers . If it was me those girders would be going into the house foundation about 6" so there would be no need for a bolted ledger board at all . i would also keep the first joist and decking about an inch or so from the main house siding or bricks so the rain water or melting snow could drain and there would be no need of flashing other that over and around the main girders . Also if framed correctly there would be no need to attach the deck to the bay window . I did this on my own house when i build it and passed the town building inspection with no problem .
I found this an interesting code application here in GA. However, this deck is not an IRC code compliant deck but rather an engineer or architect design (hopefully )
Also, here is the modern way to get around a bay window or chimney
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