Joist Hangers at Cantilevered Rim

[Barry Adair]

Paul,

Bottom line, good catch and call; but you knew that.

[homebild]

Originally Posted by pdickerson

Marcel,

Just about everything you said in your last post was correct. It is a short cantilever, and the rail post is bolted to the rim joist. There is no additional framing to support the rail posts.

For those of you who believe that the hangers are installed correctly, I don't think you have wrapped your mind around where the forces are exerted on a cantilevered rim. The joist is not hung off the rim, the rim is hung off the joist. The joist saddle would therefore need to be at the top of the joist for it to do any good. Also, it is important to use 3" nails (either 10D common or 16D sinker, see pic) in a double sheer hanger for the angled nails. The 1.5" nails that were used (confirmed visually at the inspection) do not penetrate into the rim joist at all! This installation maybe has about 20% of the strength it would have if installed correctly. Is it enough? Like I said, the rail felt firm but I don't like the way in looks.

Incorrect.

There is no reason to have the joist hangers placed upside down in this location because this is not the point of uplift that needs to be resisted.

The point of uplift is on the opposite end of the joist where it either connects to the ledge or at its end where it terminates if 'sistered' to another joist.

You are right that in the case of a cantilever, it is the joists that caryy the rim and not vice versa, but a joist hanger is still required at this point in the orientation as shown in oder the keep the rim board from collapsing uder the weight of loads placed down vertically on top of it.

The joist hangers are properly oriented in the photo, and to place them upside down or to not use them at all would be a Code violation.

Only unless a structural eneginner says other wise can the orientation of a joist hanger be inverted as is being suggested.

[pdickerson]

Originally Posted by homebild

The point of uplift is on the opposite end of the joist where it either connects to the ledge or at its end where it terminates if 'sistered' to another joist.

That's right, and there should be some means of preventing this uplift that would be caused by a concentrated load at the cantilevered end of the joist. But this is not the discussion topic.

Originally Posted by homebild

You are right that in the case of a cantilever, it is the joists that caryy the rim and not vice versa, but a joist hanger is still required at this point in the orientation as shown in oder the keep the rim board from collapsing uder the weight of loads placed down vertically on top of it.

Loads place vertically on top of the rim board will be resisted only by the joist hanger nails. They will not be resisted by the joist hanger saddle unless the joist hanger is installed upside down

[homebild]

Originally Posted by pdickerson

That's right, and there should be some means of preventing this uplift that would be caused by a concentrated load at the cantilevered end of the joist. But this is not the discussion topic.



Loads place vertically on top of the rim board will be resisted only by the joist hanger nails. They will not be resisted by the joist hanger saddle unless the joist hanger is installed upside down

That may be true, but inverting a joist hanger is illegal and a code violation under ALL circumstances, as has already been pointed out by someone who referred to Simpson's own installation instructions, unless it is done under the direction of a structural engineer and as part of a stamped design.

What you are suggesting for the rim-to-joist-connection of this deck is a Code Violation and can only be legally done if it has been designed by an engineer.....

[homebild]

Originally Posted by badair

This may help to clear up some of the previous information posted.

http://buildingcodes.jocogov.org/doc...eck%20Book.pdf

Here's the joist hangers at a cantilevered section of deck/carport I questioned Simpson about.

While the use of these 'upside down' joist hangers can be used to resist uplift when designed by an engineer, located as they are in the locations they are creates a code violation since they no longer provide minimum bearing for the floor joists at the girder connection.:

http://www.nachi.org/forum/attachmen...8&d=1187406803

[Richard A. Hetzel]

It's impossible to tell anything from the picture. If that is a rim joist which is out in space, then it is not a structural member, and serves primarily as trim, and to keep the ends of the joists from rotating. If it is a rim joist at the end of a cantilever, the uplift, if any, is at the far other end of the joist, so there is no reason for the joist hangers to be upside down. In fact, there is no real reason for joist hangers at all, since the rim joist isn't structural.

Depending on the loads and the relationship of main span to cantilever, the uplift on the other end may be very small, and easily carried by the nails in the joist hangers. If the cantilever is large and the main span is small, the uplift could be considerable, and as has been stated, the connections then should be specifically designed to resist the uplift.

[Marcel R. Cyr]

That's right.

http://www.arlingtonva.us/DEPARTMENT...l_Alington.pdf

Marcel