Fastening Wood Joists to Steel Beam

[VictorAK]

Can someone please comment on the following when installing wood joists:
1. placing wood joists on the bottom flange of a steel beam then "packing" the space between the joists with 2x8 or similar or,
2.fastening a wood member to the flange with bolts at 24" o.c. and fastening the joists to the wood member with joist hangers.

Thank you,

 

[JAE]

There are two choices there.
One is better than the other.
Choice number 1 isn't very good.

 

[vandede427]

I've seen both.

I'd prefer #2, to provide the top flange nailer and use a top flange Simpson hanger.

 

[enginerding]

Depending on how big your flange is, I have seen double (or triple) 2x_ bolted to the web of the beam and standard joist hangers used. This way you avoid all the labor involved with adding separate solid blocking to prevent rotation at the bearing.

 

[msquared48]

I agree to hang the joists from a nailer attached to the top flange with Nelson sill plate anchors. However, the nailer must be a 3x minimum, ripped to fit the full width of the steel beam flange.

Mike McCann
MMC Engineering

 

[VictorAK]

Correction:
1. fasten wood member to web, not flange.

 

[VictorAK]

sorry about that - suppose to be for option 2.

 

[dicksewerrat]

I'd rather see the joists attached to the top of the beam

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[enginerding]

Likewise, but I like to see them running across the top rather than hanging from top flange hangers. I know that this is done all the time with I-joists, but maybe I still prefer regular old stick framing details at heart...

It is when the homeowners or architects don't want the beam hanging below their joists that you need to do something different. I prefer full depth joist hangers to top flange hangers any day.

 

[vandede427]

1. Mike, why does it have to be a 3x, for nail penetration depths? i've called this out many times and never had a problem with a single 2x. even Simpson shows a 1.5" min nailer thickness. and why does it have to be ripped to the exact width? it doesn't matter if the nailer hangs over the flange a little. 2x6 on a W14x22 leaves only a 1/4" over on each side.

2. nerding, isn't a top flange hanger full depth anyway? they all loop around under the bottom of the joist.

 

[VictorAK]

Thank you for the information.

From what I understand, option 1. of placing the joists directly on the bottom flange should be rejected and have the contractor either attach a nailer to the web or top flange?

 

[msquared48]

You got it...

Mike McCann
MMC Engineering

 

[VictorAK]

Thank you Mike.

 

[enginerding]

vandede - yes it wraps to the bottom, but if you ever get the chance, push sideways on that bottom chord and then tell me whether you think it could be considered braced against rotation at the ends.

 

[bylar]

#2 We do it all the time.
Its called a buried beam.
Bolt 2x to web with bottom bearing on flange.
chamfer for radius.
Joist hanger to 2x./
Normally we use a double 2x if need to clear the top flange and the joist are flush to top of beam.

 

[msquared48]

Vandede427:

Sorry for the belated response.

The reason that I use the 3X is not so much for the top bearing joist hangers, but mainly for the plywood diaphragm and any sill plate nailing. I just don't have to worry about the nail lengths with 3X's.

Mike McCann
MMC Engineering