Construction question - bolted wood ledger

[AaronMcD]

Hi, for some reason I never thought of this. There is a common detail where a wood ledger is bolted to a concrete wall, and wood joists hangers attached to the ledger. Wood joists often have to be in precise locations, due to a collector, or a wall above or shear wall below, etc. If the ledger anchor bolts are cast into the wall, how does the guy placing these know where every joist will have to be? Are they really that coordinated in field, or will they do something funny and mess up the design?

 

[E720]

In my experience, at least in residential construction, the concrete guys rarely coordinate things with the framers. Because of this I try to call out a larger spacing of bolts rather than smaller. For example if the ledger still works, call out (2) rows of bolts at 32" rather than 1 bolt at 16". In addition I would suggest calling out an option for a concealed flange hanger on this detail so that it takes up less space if they need it.

 

[WARose]

Hi, for some reason I never thought of this. There is a common detail where a wood ledger is bolted to a concrete wall, and wood joists hangers attached to the ledger. Wood joists often have to be in precise locations, due to a collector, or a wall above or shear wall below, etc. If the ledger anchor bolts are cast into the wall, how does the guy placing these know where every joist will have to be? Are they really that coordinated in field, or will they do something funny and mess up the design?

In my experience, the call out on the drawing (i.e. the bolt spacing) will be so that the ledger will work regardless of where the joist(s) fall.

 

[AaronMcD]

@WARose
The question is what happens when the joist itself lands exactly at the bolt location and can't be connected?
A solution could be countersunk bolts, but I don't think that is very popular detail.

 

[WARose]

Simpson makes a bunch of ties/connections that go on (just) one side......so you should be able to miss it.

EDIT: If you are talking hitting one where the CL of joist and bolt are the same, you should be able to notch the joist. (NDS has guidelines for it.)

 

[KootK]

Without getting into fancy detailing that will be unpopular, I don't see how the need for coordination can be avoided in these instances. A note on the drawings calling attention to a non-negotiable member tie in location is probably prudent. When there's a problem, my money says that the offending bolt just gets cut off.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Celt83]

either design the anchor spacing on a different module than the floor joist spacing or provide a 2-ply ledger with the anchors countersunk in the outer ply and use top flange hangers. The 2-ply takes some additional detailing and I like to include some moment in the anchor design if I go that route but it gets rid of the potential conflict.

I've also gone the route of designing the floor sheathing to span an extra 6" to give the guy laying out the joists 3" of play in either direction so they can adjust on the fly.

Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

 

[hokie66]

I'm surprised at the question, because I haven't seen bolts set for a ledger in a concrete wall. Post installed anchors are more practical, I think. Ever try to exactly match holes in a wood member to preexisting bolts?

 

[KootK]

Ever try to exactly match holes in a wood member to preexisting bolts?

They hold the boards up against the bolts and give them a whack with a hammer to make imprints. But yeah, definitely some logic in the post installed.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.