Bowed gable-end truss
Today we got 18/19 trusses set and somewhat braced, more to go on bracing.
The problem we ran into is that the gable and would meet the wall in the middle, but both ends were off the walls. The walls are straight and flat.
I pulled the gable down and snapped a chalk line along the bottom of the bottom chord, and found that the center was lower than the ends by a good 3/4″.
Having never set a pre-buiilt gable truss, I would think that it would be nearly impossible to load the top chord enough during installation to push the bow out.
We are considering making the truss company set the last truss assuming this bow is not normal, since we’re already out 2 fulls days of JLG rental and hired friends help. Is it normal for the gable to bow in the middle?
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Replies
Mike,
No. When the trusses are delivered the bottom chord should be perfectly straight. You may get seasonal lifting of the trusses (which is why you don't nail them to your interior walls), but this is a slight upwards curve, not a dip. Now given that the gable truss isn't really load-bearing I'd bet that the truss manufacturer will simply snap a line and cut the bottom chord straight, but that's something for them to do not you.
Malcolm this gable is.actually land bearing according to the Mitek prints it has loads at 10 or so points. All of the other trusses including studio style were only load bearing at the ends.
Yeah, but they all transfer down to the walls below. The bottom chord isn't in tension like the rest. I bet they just trim it straight.
Get the truss in place and use a pipe clamp at each end to suck it down against the top plate. Fasten it and sheet it.
Dave, We tried pipe clamps but could not exert enough force to bend it down enough. When we finally got close it ripped the nails right out of one side and popped back up. We even tried using a tow strapped attached to my Bobcat as a last ditch effort. It flexed it enough to sit flush, but instantly ripped all nails out on the opposite end and pooped the clamps off.
Mike,
One thing to check is how the top chords plane with the rest of the trusses. If the bow transfers up to the top then you need a new truss.
Malcolm,
I laid the level acroos the top of the previous few trusses, roughly the same height from the tails, and had at least and inch or more above the previous ones.
We are working with the lumber company now. I was not overly happy with the truss company as they initial had load bearing interior walls which was specifically requested against. The first truss order had 2 of 5 different trusses it was supposed to. When they got the order close, they dropped the trusses directly in a muddy area, exactly where we needed the equipment to set them. To top it all off the fail designs were not the same we originally ordered and they sint provide the new diagrams for bracing or layout. We are hoping they will eat the cost to install the gable. Luckily it's an addition so e have some support from the original gable, which is where we started (as opposed to setting the gable).
I should also note the gable was sheathed on a flat surface with spacers to keep it level and from sagging or getting too wavy.
Mike,
One of the main advantages of trusses is not having to worry about this sort of stuff. Too bad they let you down. Hope things go more smoothly as you get further along. Good luck!
Mike, it's not uncommon for trusses to need a little persuading, but it sounds like you got a bum deal and the truss company should make it right. Ordinarily I would want to sheet a gable truss on the ground rather than after installed, and would sight the bottom chord for straight before doing so. They are making a serious headache for you. Trusses are laid out and assembled on large jig tables, and there's no excuse for them being out of shape.
The truss company recommended cutting the truss, about an inch or more off the bottom in the middle and shim/sister a 2x4 as necessary.
They are going to discuss covering costs for a boom to lift it,