I recently had a deck built. The deck has a few places where double joists are used between beams to allow cutouts for trees. The framers used single joist hangers for the 2×6 16" oc joists.
On the doubled member they just added another member to the joist that was already hung with a single hanger. Is this common practice? – I would never have thought of doing that.
2x6s are less than 7' span between deck beams. Deck beams are 19' 2x12s on outside. 11 7/8 PSL at house and in middle.
Blue arrows to area with doubles framing around tree.
Best Answer
No, it is lazy. A double joist hanger should be used for a double joist with few exceptions. Whether it is legal or not depends on how your state and local community have developed, adopted, and interpret building codes. From a structural standpoint it may be insignificant under certain conditions.
Is it worrisome: an engineer would be your best source but generally no if the structure is maintained and you inspect it regularly. Joist hangers are a component of a system and their absence or improper installation don't mean catastrophic failure by themselves. It is not uncommon in older structures to see double joists tied into single joists to avoid an obstacle. All without hangers.