Lifting Truss Roof, best place to lift from?

[DavidSand]

I have a job where we are going to be adding a second floor to a garage. The plan is to lift the existing truss roof off, and set to the side, and then put back on after the second story is added. There are 16, W-type trusses 24" OC, the bottom cords are 24'. We plan on putting 2 strong backs 12' apart, that are 6' to either side of the ridge, to use for the lift. We will lift at two points on each of the strong backs, so there will be 4 points that carry the load. (~3,200lbs, truss & sheathing, shingles have been stripped). My question is, is it best to set the strong backs on the bottom cord at the intermediate gussets, or the top cord near the where the intermediate member meets. Thanks for you thoughts.

[David Meiland]

Re: Lifting Truss Roof, best place to lift from?

Your plan sounds OK. I would pick it up by the strongbacks, but I would put the strongbacks (2x12s standing up on edge) as close to the wall lines as possible, and screw in a bunch of hurricane ties temporarily so that the strongback is lifting the bottom chords and not putting any stress on the truss plates, and also to keep them from rotating.

[DavidSand]

Re: Lifting Truss Roof, best place to lift from?

Thanks for the info. I will plan on putting the strong backs under the bottom cord, so that when I set the roof down on piers for storage, it will sit on the strong backs and stay flat and true.

[David Meiland]

Re: Lifting Truss Roof, best place to lift from?

So you are going to cantilever the last couple of trusses at each end...

[Dancing Dan]

Re: Lifting Truss Roof, best place to lift from?

If you can still find a manufacturer's tag, I'd put in a call and see if they're willing to give you any advice.

[DavidSand]

Re: Lifting Truss Roof, best place to lift from?

The strong back will pick up the load on all the trusses, except the two ends.

[jimAKAblue]

Re: Lifting Truss Roof, best place to lift from?

I have a job where we are going to be adding a second floor to a garage. The plan is to lift the existing truss roof off, and set to the side, and then put back on after the second story is added. There are 16, W-type trusses 24" OC, the bottom cords are 24'. We plan on putting 2 strong backs 12' apart, that are 6' to either side of the ridge, to use for the lift. We will lift at two points on each of the strong backs, so there will be 4 points that carry the load. (~3,200lbs, truss & sheathing, shingles have been stripped). My question is, is it best to set the strong backs on the bottom cord at the intermediate gussets, or the top cord near the where the intermediate member meets. Thanks for you thoughts.

I've hoisted a lot of stuff. I wouldn't spend any time trying to create two 30' long strongbacks.

I'd most likely cut the roof in half. Each section would be 16' x 24'. I could grab that by wrapping the top chord in two places and dump the section anywhere on any surface.

The re-installation would require that I scabbed a 2x4 onto the side of one of the trusses and nailed the ply joints securely. The entire operation would be fast, furious and easily managed.

My philosophy evolved because I've lived the life, working with others, that thought "build it bigger and lift/hoist it". My varied experience with these issues led me to the philosophy "Just because you can, doesn't mean you should." Essentially, in this case, I would conclude that: yes, I could hoist the entire roof as one unit, but there's really no significant reason why I should. I then would compare the time spend rigging and also the risks. Also, the size of the crane would become a consideration.

But, if you want to hoist the entire roof in one lift, I'd probably opt to put the strong backs under the bottom chords. It will be relatively easy to get them there and easier later to knock them off. I don't think the weight of the entire assembly is any significant thing. The larger issue will be the propensity of the thing to sag, but that will re-take it's form when you set it on the new, level 2nd story walls.

[TSJHD1]

Re: Lifting Truss Roof, best place to lift from?

Those trusses would have been set originally by picking them at the peak... you can lift the whole assembly the same way, provided you just attach some strongbacks like I've drawn. Use a spreader bar, and if possible pick at 3 points, using some short pieces of steel. They wouldn't need to be very beefy, just enough to spread the concentrated pick point. 2 pick points at the ends of a spreader bar would most likely work also. Just move the end locations inward somewhat, and use longer steel than if you were to pick using 3 points. And attach some diagonal bracing through the trusses attached to the tops of the bottom chords.

Actually, you could just get a treated 6x6 and use either 2- 6' pieces, or 3- 4' pieces in lieu of the steel. I don't agree with picking at the bottom chord, because you would need to locate the rigging very near the truss bearing points, and then you've got the added issue of the lateral loads you would be imparting to the trusses. So you'd need to somehow lift in a vertical line, and now you're talking about more than one spreader bar, or you'd have to rig something so the lines would not want to slide.

That roof is going to be a whole lot more stable hanging from its strongest connection than anywhere else, imo.

Tom

[TSJHD1]

Re: Lifting Truss Roof, best place to lift from?

Couple of pics from the last truss roof I set... very similar to what I'm describing here.

It's not strongbacks you see in the middle. There is a center girder truss, ala a 5' tall ridge, and the main trusses are in 2 halves.

Tom

[David Meiland]

Re: Lifting Truss Roof, best place to lift from?

Tom, you're hired, when can you start?

[Mark Parlee]

Re: Lifting Truss Roof, best place to lift from?

Here is one we did where we removed the roof before doing the remodel addition.

https://picasaweb.google.com/thebuil...shworthRemodel

[Chopper]

Re: Lifting Truss Roof, best place to lift from?

I've hoisted a lot of stuff. I wouldn't spend any time trying to create two 30' long strongbacks.

I'd most likely cut the roof in half. Each section would be 16' x 24'. I could grab that by wrapping the top chord in two places and dump the section anywhere on any surface.

The re-installation would require that I scabbed a 2x4 onto the side of one of the trusses and nailed the ply joints securely. The entire operation would be fast, furious and easily managed.

My philosophy evolved because I've lived the life, working with others, that thought "build it bigger and lift/hoist it". My varied experience with these issues led me to the philosophy "Just because you can, doesn't mean you should." Essentially, in this case, I would conclude that: yes, I could hoist the entire roof as one unit, but there's really no significant reason why I should. I then would compare the time spend rigging and also the risks. Also, the size of the crane would become a consideration.

But, if you want to hoist the entire roof in one lift, I'd probably opt to put the strong backs under the bottom chords. It will be relatively easy to get them there and easier later to knock them off. I don't think the weight of the entire assembly is any significant thing. The larger issue will be the propensity of the thing to sag, but that will re-take it's form when you set it on the new, level 2nd story walls.

Jim, After setting thousands upon thousands trusses, I concur with you exactly, just because you can, does not mean you should...

[DavidSand]

Re: Lifting Truss Roof, best place to lift from?

Those trusses would have been set originally by picking them at the peak... you can lift the whole assembly the same way, provided you just attach some strongbacks like I've drawn. Use a spreader bar, and if possible pick at 3 points, using some short pieces of steel. They wouldn't need to be very beefy, just enough to spread the concentrated pick point. 2 pick points at the ends of a spreader bar would most likely work also. Just move the end locations inward somewhat, and use longer steel than if you were to pick using 3 points. And attach some diagonal bracing through the trusses attached to the tops of the bottom chords.

Actually, you could just get a treated 6x6 and use either 2- 6' pieces, or 3- 4' pieces in lieu of the steel. I don't agree with picking at the bottom chord, because you would need to locate the rigging very near the truss bearing points, and then you've got the added issue of the lateral loads you would be imparting to the trusses. So you'd need to somehow lift in a vertical line, and now you're talking about more than one spreader bar, or you'd have to rig something so the lines would not want to slide.

That roof is going to be a whole lot more stable hanging from its strongest connection than anywhere else, imo.

Tom

Tom - I originally considered what you have outlined above, but was concerned about the outward forces placed on the top cords at the ridge gusset. To me lifting from the ridge line makes the most sense from rigging and balance. What are you thoughts?

[TSJHD1]

Re: Lifting Truss Roof, best place to lift from?

To me lifting from the ridge line makes the most sense from rigging and balance. What are you thoughts?

Well that's what I'm saying- lift from the ridge line. The only "outward forces" in addition to the dead load of the trusses themselves is the sheathing. And on a per-truss basis, each top chord is essentially carrying the added weight of a 2' rip of sheathing, about 15' long (depending on pitch). That's nothing.

I am absolutely positive this roof can be picked just like I've outlined, as long as I've got the trusses drawn correctly, and you have no more weight other than the roof sheathing. I didn't really give too much "weight" (ha) to the gable trusses... they are a bit heavier than the "field" trusses because they have extra framing and they are sheathed. But as long as you run the strongbacks through them as well, they won't go anywhere. It probably would be a good idea to run them beyond the gable a foot or so.

You'd be surprised, so to speak, how strong a truss roof is once it has roof sheathing applied. Just as the 2x4's that make up each truss are not very strong individually, once they are attached to each other via truss plates, that truss works as a system. The same is true for the roof as a whole once the sheathing is in place.

If you wanted a bit more peace-of-mind, then attach 2x4 collar ties to 4 trusses.

If it was my job, while that roof was on the ground, I'd install the drip edge, ice and water shield, and felt too.

Tom

[TSJHD1]

Re: Lifting Truss Roof, best place to lift from?

Tom, you're hired, when can you start?

Don't tease me David...

Tom