Hi all, (and especially Boss)
What is the currently accepted ‘best practice’ for attaching scissors trusses to the top plate? Simpson makes a variety of connectors that look like they can be used, but there seems to be a conflict between making a nice solid connection – say with a hurricane tie like the H10, and letting things slide around as the truss moves, like with the TC26. Any suggestions out there?
Loach
Replies
Well, you've hit on an issue that really ticks me off.
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(This is what you're talking about, right?): http://www.strongtie.com/products/connectors/tc_pt.html
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To me, those Simpson "TC" hold-downs are utterly ridiculous. I've even asked people from Simpson about them, and they can't tell me what they're suposed to accomplish.
The theory sounds good at first - Let the end of the scissor truss slide back and forth as load is applied to and removed from the trusses. But what the hack happens to your drywall joint on the inside of the building ???
And what happens to your soffit material while these trusses are sliding back and forth?
Typically, residential scissor trusses don't have enough horizontal movement to make a bit of difference. So I think it's ridiculous to use gimmics like these TC things.
Industry standards (TPI) only allows a maxim of 1.25" of horizontal deflection on scissor trusses. And that's under full design load. Once the trusses are installed and the roof is on, probably 1/2 to 1/3 of the design load is already there. So future deflection is not going to be the full 1.25" allowed. (Assuming the truss is right at the limit)
I've never once in my ~20 years in the business heard of horizontal deflection being a problem in scissor trusses. So to me, these things are designed to cure a non-existant problem. And they create more problems in the process.
Need a good screw? [Ace Hardware]
Yep, Boss, those are the connectors. I also find it hard to believe there could be that much movement, and it would sure be a lot easier to not have to be worried about it. I think the soffit would tend to box the ends in and limit movement, also. By the way, what is the best way to attach these guys to the top plate?
Loach
"I think the soffit would tend to box the ends in and limit movement, also."
Around here, soffit material is generally just light gauge aluminum. So I doubt it could resist any force to speak of.
I was more concerned that the soffit would fall out of it's slots if the truss moved outwards.
"By the way, what is the best way to attach these guys to the top plate?"
I'd attach them just like you do any other truss.If you don't have a sense of humor, you probably don't have any sense at all.