Top chord bearing wood floor truss attachment to ledger on CMU?

[disoswam]

thread507-352349

How would you attach top chord bearing wood floor trusses to 2 ply 2x wood ledger bolted to CMU 2 story wall in high wind? How would you attach 3/4" osb floor deck to the ledger? Blocking between trusses? Or maybe just lag screw the top chord to ledger, nail floor OSB to trusses only? Since this floor is a horizontal diaphragm it seems nice to nail the osb to ledger somehow. I have used top flange buckets with Ijoist and nailed osb to joists and ledger since they were all on same level but in this case top of truss is 3" above top of ledger.

 

[msquared48]

1. Strap trusses to the CMU wall at 48 minimum, nailing either to side of truss or top of top chord.

2. Provide solid blocking between the trusses above the ledger extending to the plywood diaphragm and nail off. Nail the diaphragm to the blocking and the blocking to the ledger.

4. I would use a 4X minimum ledger, not multiple 2X's.

Mike McCann, PE, SE (WA)

 

[Triangled]

i like mike, and really support his 4th point

I am supposing you're using an MPC truss based upon your 3" top chord thickness, sometimes I've used a hanger like the pic below for a nice diaphragm transfer, but I think blocking like mike might be less expensive with 2 layers 2x blocking properly nailed

 

[jayrod12]

I would change the double ledger to a single bigger as well (Moreso deeeper than wider for me), then use the flush mount hangers like Triangled shows. That way you can run your sheathing to the edge of your ledger and fasten it that way.

 

[msquared48]

Actually Triangled, that was my third point. I just can't count...

Mike McCann, PE, SE (WA)

 

[disoswam]

Thanks everyone for the good advice so quick. I'm going to spec 4x6 ledger, 2-5/8 anchors @16"OC, 2 - 1/4"x6" screws top chord to ledger, 2-2x4 blocking nailed 4"OC to ledger and 3/4" OSB floor deck. for the CMU wall parallel to 32'x24" floor trusses: 2x6 ledger with 1/2" anchor@24"OC, LTT20 tension tie @6'OC with blocking and CS20 coil strap back to 3rd truss from wall.

The truss design shows 3.5" bearing but designer said that is 3"bearing+.5"gap. He reran truss for 1.5" bearing and 2"gap and it worked? He said 4x6 ledger may be more cost effective than glue and screw 2-2x ledger and only one piece to put up. And they would likely put the SDS screws into crack between 2-2x every time? Since Florida is not seismic I did 6'OC tension tie to parallel CMU wall instead of 4'OC and SDS screw top chord to ledger on the perp walls.

 

[disoswam]

Woodworks connection said put top bolt 2.6" from top and lower bolt 1.88" below that or 1" from bottom; 16"OC is good for 1048plf. Seems pretty precise locations in 4x6 so I changed to 4x8. I specked 3x3x.25 washers on top bolt to avoid cross grain bending. I sometimes wonder how they attach ledger with wet set anchors and match drilled holes 1/16" bigger than anchor per NDS. Inspector probably is OK with 1" holes for 5/8" bolts.