Deck support at angle to joists

[haynewp]

I have gotten involved in a project where the joists were laid out perpendicular to the roof slope. The slope is slightly over 1 to 12. I am placing bent plate seats so the joists can sit horizontal and giving the joist fabricator the option to provided canted seats instead if they wish.

However, the issue now is that there is a point support of the deck at the very edge of the joist top chord. The deck may still be able to be screwed down, but I think it may bend from the dead and live load at this point support.

 

[haynewp]

Has anyone dealt with this before and did it end up being an issue? The only idea I have is to place a wedge plate along the top of the joists, but it would have to be very thin and costly to install.

 

[KootK]

I could see this being a problem as you're well outside of SJI recommendations. I'd give them a call and see if they can offer up any kind of solution.

Are things too far along to consider altering the framing layout or tilting the joists which, admittedly, has its own problems?

 

[haynewp]

I got involved at a point that was late as far as the framing direction and I have never framed joists like this before. Thanks for the SJI idea.

 

[r13]

I would use solid wedge plate. Difficult to get though, I guess.

 

[haynewp]

I talked to SDI and that is what I am going with, a continuous steel wedge plate.

 

[Agent666]

That sounds kind of expensive to fabricate as you'd have to presumably mill the taper and if its full length then you're talking a lot of milling, what's wrong with the same wedge but in timber. Fix roofing with longer self drilling screws into the Joists through a timber wedge?

In this part of the world you can get self drilling roofing screws specifically for this purpose to fix through sheeting, then timber and into 5=6mm thickness of steel. Maybe something similar exists in your local area.

 

[haynewp]

It's Federal, this division normally excludes the use of structural related wood in the scope or later rejects. This project is actually a replacement of partially rotten wood trusses.

 

[KootK]

I'm curious now:

1) Any idea how a taper plate is fabricated or what it costs?

2) Will this dictate puddle welding over pins?

 

[r13]

The wedge plate can be made thru machining, could be quite costly though.

 

[phamENG]

I've managed to not need to turn the joists the wrong way, so I'm not familiar with all of the problems tilted joists bring with them. But...the problems I can think of could probably be dealt with close attention to some extra bridging. Seems cheaper than bent plates everywhere and continuous steel cant strips on every joist. Am I way off on the scale of the tilting problem?

 

[jayrod12]

1 in 12 is a pretty tall order for joists to be tilted if I remember correctly. I dont have stuff here, but I feel that 3 or 4% was the maximum.

 

[KootK]

Am I way off on the scale of the tilting problem?

It's been done and I proposed it at the top. It gets a little weird for erection though and usually results in permanent axial load getting dumped into your deck.

 

[haynewp]

I have no idea on the costs, I was reassured by SDI that this is done in such cases and it can be fabricated. It may take welds due to the base steel thickness.

When I called a joist mfr they said they would not design the joists for the weak axis bending component if the joists were to be tilted (along with seat difficulties)and highly discouraged it for the slope I have. Smaller slopes would not be an issue they said.

 

[haynewp]

Weak axis component we discussed was in the bottom chord between such bridging.

 

[phamENG]

Fair enough. Thanks for letting me learn from your thread. I guess at that tilt you'd probably need bridging every other panel point...

 

[r13]

haynewp,

Ask the metal supplier, it is similar to wedge washer, available through special order.

 

[IFRs]

would standard beveled washers just happen to be the right slope?

 

[dik]

Can the joists just be tilted if angle isn't too great? or, have OWSJ supplier provide the angled base... likely the least costly.

Dik