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I am looking for a better way of installing piggy back trusses. The common installation technique here is to install the flat top trusses as you would install ordinary commons. Then lay down the runners or plates that ties the flat top trusses together and provides nailing for the piggy backs. Its tedious and time consuming and doesn’t work with my installation system.
I like to mount the gable piggybacks to the gable trusses on the ground, then install my rake fascia and anything else that can be fabbed on the ground (returns, bird boxes etc.). I asked the engineer at the truss plant why we can’t install the piggybacks to the rest of the flat tops before we crane them up. He said that the runners are required for the truss design and the would be impossible to thread through the piggybacks.
I asked what the difference would be if we nailed them on underneath, in the course of our normal lateral bracing installation. He couldn’t give me an answer.
I’m going to pursue this further, but I was curious as to what other guys are doing.
Anyone care to share their thoughts?
Tom
Replies
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Tommy...the first thing that comes to mind when reading your post is safety.It seems to me that if you install the piggybacks on the ground it would take a tremendous amount of bracing to hold these in place.The bracing would not only have to be lateral but you would also have to install some type of gussets to keep them from actually collapsing.?Most of this would also depend on the size (height) of the piggybacks also.Is this something you really feel comfortable doing?Aren't the piggybacks designed to allow for the 1-1/2" nailers? You could have a problem with the tops of the piggybacks lining up with the flat top trusses.?
*I installed a number of piggybacks last year and couldn't figure any other way to do it than your original method. The truss prints specifically showed the runners as required bracing, and the inspector checked for them. Also, since they piggybacked on 32' wide attic trusses, I'm not sure if me and my two guys could have gotten them up, had they been any heavier. Do you get truss specification sheets that show the required bracing?
*Jerry,I'm a safety freak, and I do feel comfortable doing it. As always its a matter of trade offs, and part of my reasoning is that it is safer to do on the ground. The way my piggy backs come (and I would assume all others) is that the top chord is long to allow for the 2x runners. Of course I have to gusset or scab some 2x on to hold the piggy back on but I can lift on the flat top truss if need be. Like I said I already do this on the gables and its not a problem. Jason, yeah I get a bracing diagram with my trusses and I follow it.Since you guys seem to be on the same page, I guess my question is why does it matter if the runners for the piggybacks are on the top of the flat top trusses, or underneath that same top chord. Basically I'm looking for a better way, and to do that you have to question the old way first. I like to question everything which has yielded good results for me so far.Tom
*> does it matter if the runners for the piggybacks are on the top of the flat top trusses, or underneath that same top chordNo. They can be either place. The only potential problem I see is that the caps might need to be made differently. They're actually made to bear on the 2X4 purlins, no on the extended top chord. You truss supplier can make them differently if you're going to do this. But it seems to me that you're just creating another problem by doing this. After you set the base trusses with the caps attached, won't it be a nightmare to get up there to put the purlins on the underside of the top chord ? If your base trusses are 12' tall or so, there's no place to stand while you nail those suckers on.
*Ron,I could not see any difference whether they are top or bottom mounted either.As far as attaching them goes, I still think I can save time there. If you stock your plywod in the webs to sheet the roof, you'll have a platform to work from. Also, if you wait till the roofs sheeted, it makes it easier to get the sheets out. I think it will work out for me.Thanks for the input. Tom
*> If you stock your plywood in the webs to sheet the roof, you'll have a platform to work from.Never heard of doing that. I guess it would work, as long as you don't overload the trusses. But you still wouldn't be able to reach the underside of the piggyback trusses, if they were roughly 12' tall. If you were on top of the trusses, the purlins would simply lay there until someone nailed them in place. If you put the purlins under the top chord, you would probably need 2 guys to hold the boards up and nail them in place. Are you sure you've gained anything ?
*Ron,Yes. How have you seen guys handing sheets onto that same twelve foot truss? Do they hand them from the ground, or up form the deck? Do they cut on the roof? I have heard of guys stocking plywood right on the bare trusses and cutting there, but I don't see how it would be more efficient, especially on the steeper pitches that we build. I'm always looking for a better way if you have one.It takes me all of eight minutes to stock sheets on the bottom chords. Then we make a few piles to cut off of. We never put more than 6 tons directly on any one truss at midspan(I'm kidding). Tom
*What would concern me is someone (like me) standing on top of those lateral braces (which are nailed from below) before the sheeting is installed. Just a safety issue. I just did my house and am sheeting it now, my piggy backs are ten foot wide so I had to run five braces full length on the top cord. I climb all over them and I'm glad nailed from the top.Sylvan
*Ahh Tommy, a topic that interests me!I've done a lot of piggy back riding and am lost as to your concerns. I'm also confused too about your stocking the bottom chords.Anyways, heres what I do.I also preconstruct the gables and complete the exterior siding and overhang prior to erection.The largest piggies that I have installed were 40' 9/12's. They required 11 lacers on top. That would have been hell to do any other way than your base method. On those, I rode the top and installed three lacers before we released the crane. There were several other guys lacing down below. I then staggered back all the remaining lacers and generally was able to keep up as we went. If the crane can drop you the lacers, they can easily be installed.I generally ride on top and do all the lacing before the crane leaves. We also manage to install the necessary diagonal bracing (temperory or permanant) to drop a load of sheathing on top of the lacing. The pigs just lay in a pile till we run the sheathing.I sense that you use a cut man for your sheathing. The pile on top of the trusses would be ideal. We don't use a cut man. We carry our sidewinders to the cuts and cut in place. Experiments has showed that it takes twice as long to use a cut man and I can't afford to ignore the evidence. I can sheet an entire roof without a tape or chalkline and wouldn't do it any other way. And I'd prefer to work on 12/12's rather than 9/12's too (the work is closer to me and I don't have to bend).Anyways, on one job, my guy failed to get the lacing right. He had to go bck and slip those extra lacings on in between the trusses. He learned fast how to do it right.blue
*Blue,Wondered why you didn't respond to this when I posted it. This time of the year I bet you spend your evenings burying jars of money in the yard.I here ya on riding the piggybacks I just think it would be more efficient to skip that whole step and nail them to the commons on the ground.Yeah, I've given serious thought to stocking sheathing up there, but I have never seen it done here and I would likely meet some resistance with help, etc. I stock sheathing in the webs, usually there is enough room, and it makes it easier to get it to the lower parts of the roof. There may be some other regional differences that would affect roof sheathing procedure. For example, do you paper the roofs? Here, that is the framer's job. On steeper pitches, we felt as we go, a giant pain in the ass. Why don't you explain how you go about sheathing a roof in without a cut man and sheets up on the flat. If you can beat it into my neanderthal head that is.Tom
*I know the flat tops of a piggyback system make a heck of a good place to stock some plywood. But make sure the trusses are braced well - especially the sloping top chords. This is also an ideal way to have your roof collapse without adequate bracing.
*I agree Ron! It is very easy to make a freestanding set of trusses top-heavy and collapse them. To prevent a disaster, I install enough braces to adequtely prevent a collapse. I usually err on the side of caution and I usually don't put more than thirty sheets one one set. Even thirty sheets is dangerous though!I am interested in stocking some into the webs as tommy does. I've never done that but it has me thinking!blue
*Tommy, we luckily don't have to felt. I agree, it would complicate the job tremendously.I don't mind riding on top. We use 2x4x925/8" lacers and generslly set two trusses at a time with a crane. I lace the trusses on top and extend the lacer out to catch the incoming truss. I usually can release the crane in ten seconds or less if the guys are good at guiding the trusses down to the correct spot. I then just hold the second truss's top from falling away as they move it into it's postion. I then install a new lacer, hanging it over 24" to catch the next incoming trusses. There is "wasted" overlay using this system but the studs are much easier to keep from falling off their staged postions. I used to use 25 1/2" blocks but switched to this msthod years ago.The studs are used for kickers on steep roofs while sheathing unless they are left for piggy flat top lacing. Anyways Tommy, try stocking a very small amount of plywood up on the flat tops. Be caareful about having it braced though. I've never staged any up ther without all the top lacing intact and the all-important diagonal bracing installed too. I usually install additional bracing directly under the load while making sure the the loads are transferred directy to the deck in some way.Here's how I sheet a roof without a cut man. The most important item for me is kickers. I put one stud on every sheet, the instant I lay it. That gives me solid footing for the inevitable cuts that I will have to make. It also is a good place to lay my stapler (I staple each sheet as I lay it too) and my saw although I usually dig my saw in by burying the blade. I then simply lay the sheets and do all the cuts in place as needed. There is one area that I pre-cut my sheets. That is in the valleys. Since all valley cuts can be predetermined, I like to cut enough of a stack to do all the starts of each valley. We typically have several reverse layons to sheet and I find it really fast to precut and stage 6 pieces. I then lay them in the valleys and work my way out to the gable. This technique was offered by another carpenter in here. It is a very valuable tip. I've been doing it for many years.In fact, I "raced" a co-worker on the last house that we did. He typically works from the gable to the valley, leaving an awkward piece to maeasure and cut. I tried to explain to him the advantages, but he was resistant (stubborn). So I decided to show him instead of telling him. As he started measuring his piece, I dropped down to the deck and layed three sheets on the deck. Since this was an equal pitched 12/12 roof, I knew the cut of the ply is 12/17. I quickly whacked the three pieces roughly in half using the 12/17 cut. I then staged the 6 pieces up into the webs and jumped up and started laying them, walking up the valley as I went. I was able to install all 6 pieces as he finished measuring and cutting and installing his ONE PIECE!!!These rough cut pieces still needed to be trimmed half-on a truss, but it was easy to see that I could easily out lay him by at least 5 pieces to one using this one technique. I did a unscientific study of using a cut man at one time. I sent an equal carpenter on one side of a garage to lay and cut in place. I, stayed on the other side with a guy on the roof. I was the cut man, and had many sheets premarked and generally stayed very busy. My roof man was measuring and telling me the dimesnions for the next piece before I'd hand him the cut piece. There was no way to speed up our process.We took one hour and 15 minutes to finish our side (a total of 2.5 manhours). The man working alone, laying and cutting in place did his side in one hour!I conclude that it takes a substantial amount of more time, and is not safer.blue
*Blue,I appreciate your thoughts on framing topics. You're right, I need to throw a stack up there and try and cut off the roof. Unless the wind is gusty, all that dust makes traction and felting a bitch at times.I would jump at the chance to come out and scrote on one of your frame jobs. Tom
*Tommy, I carry a blow tool with a long nozzle that I occasionaly put on the end of my air hose and clean sweep the roof that I'm walking on. We just set a house full of weird (that means hard) trusses. There were about 15 piggies with a 4 foot span and three with a 30' span. That's a record for me for diversity!Anyways, we immediately blocked (at 2' intervals) the 30 flat tops and set the pigs. But I ran the blocking and staged thirty sheets on top of the 4' flat tops. It's just nice to have a supply near the top. It saves a ton of energy when we finally get near the peak and the ply is already there! I did scrutinize the possibility of staging some plywood in the webs. We did put about 15 sheets on edge in between the 30' pigs on the lacing. I'm probably going to find a significantly different method of staging plywood due to your suggestion of putting some in the webs. This job just didn't warrant it. This was easily the hardest truss set that I've done in two years. I paid a crane for 8 hours and that included setting the steel on the next two jobs.I'll make it up on the next. Since I've purchased a digital, I'll start taking pictures of some of the different things that we do. That may be the closest that you'll ever get to stand one up with me. Really though, I don't do too many things different than most of the crews here in Metro Detroit. A few tidbits here and there do add up to big bucks however!Grandpa Blue
*One suggestion hit me which hasn't come up yet, and may (occasionally) make your life a bit easier. When we get a job where the trusses b just barelyneed piggybacked, I generally call the contractor and offer a couple of suggestions. First, reduce the pitch just a touch. Some times going from 8/12 to 7.9/12 (or something like that) is enough to eliminate the need to piggyback.Sometimes leaving the overhang off is enough to get the trusses built in one piece. Most contractors I've dealt with would rather scab on the overhangs than deal with piggybacks. One or the other of these suggestions may have worked for Blue on his job that had some 4' span caps.One other suggestion - If the trusses are less than 14' tall, and you supplier tells you that they have to be piggybacked, check with another supplier. Some plants have tables 14' wide, and some only 12 or 13'.