I have been watching the big builders in our area frame entire truss roofs on the ground (plywood and felt, too) and lift them all at once with a crane onto the house.
What are the pros and cons of this method? – my next house is a simple box (32×48 10/12 pitch) no dormers etc and I would gladly pay a crane to avoid carrying all that plywood! With trusses this big I am paying the crane anyway. It seems like a big speed and safety advantage to be on the ground, too.
Has anyone out there done this? Where do I look for info? (I have searched the archives)
-Brian
Replies
My brother placed one backwards once, his GC wasn't too upset since he had came close to doing it a few times himself.
Mike
It's O.k. to think out of the box, Just don't walk off of the plank!
Holy moly...how big a roof...how do they sling it....no rafter tails, i'm guessing...& what about all those cut up McMansion roofs with way to many doemers,gables, steps, etc....
never heard of this. Can you build this trusses and sheet and felt them in the parking lot?
This is something that's done more and more often. Crane's are smaller and less expensive and easier to get on tight sites than in years past. And more roofs are being built with trusses, so it's becoming more practical all around.
The pros are obvious: easier, safer working conditions at ground level; less time spent on ladders hauling stuff up one piece at a time; and of course, much less (if any) staging required.
The cons are not so obvious. Yes, it's possible to put one on backwards. Oopsie! But that's not all. What if you don't build it the right size? Suppose your crane operator drops it in place and it doesn't fit? Really big oopsie....
You best be very sure of your framing and layout skills before you try this one. It's equivalent to pouring a new foundation for an existing house, and then moving the house over it and dropping it in place. If it doesn't fit, you R scrooed....
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
That's similar to after cutting some vinyl/linoleum and rolling it out you can only say ' hey, how'd that happen?'
Only the cost involved with a roof or foundation would be crying ground.
sobriety is the root cause of dementia.
I have been a commercial carpenter for some years now, and though I have seen, and used, this method of construction building large walls I would not be very willing to try it with a roof. The room for error is great, and the potential cost, if a mistake is made, even greater. Although it would be a WHOLE LOT easier, I think I would stick to conventional Truss Framing methods.
There must be some members out there from Alberta. My brother lived there for a couple years and said it is very popular there. I would never try it myself unless I had someone with me who was experienced with that approach. I did see it done once, when they were building a church nereby. I drove by one day and the whole roof was sitting in the parking lot ready to go!
During the brief time that I spent framing in and around the Greater Denver area, we saw several contractors using this same basic concept.
However, I didn't see anyone completing the entire roof on the ground. They only connected several trusses together using 2x10 or 2x12 stringers along the top of the center web and then stringers and friezeblocks along the eaves.
I thought is was a splendid idea.
The times I have seen it done here, everything was done in the parking lot, right down to shingles and trim. Only things not put in were the dormer windows....
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
A couple of years ago on one of the TV home improvement shows they had a story an a large victorain house that had a major fire. I think that it was 3 1/2 stories, with a very complex roof.They figured that they could rebuilt it until they figured the cost of the roof.Ended up using trusses and building the whole thing on the ground, including shingles. Then lifted up in place.I don't remember the exact details, but IIRC they saved $50-75k and that made the rebuild doable. Otherwise it would have been tear down.
I'm really intrigued by the idea - maybe I'll call the crane company and see if they have any thoughts or warnings. My main hesitation is how to tie and brace things well... I'm certain I can measure and make things fit. I mean the modular companies have it a lot harder and they succeed.
But if its gonna be a pain or a source of excessive worry, maybe I'll just do it the way I've always done it.
Oh but the time and safety savings are so compelling...
I've done just that for over 20 years now. Dozens of houses. All had one common element, they were simple gable roofs. I did them on the ground because they were all 2 stories on pilings. We built all th ewalls on top of one another on the deck then built the roof on top of that. When the crane arrived we would swing the roof off and set if where ever we could including in one case, the road. We raised and propped the walls one at a time then picked up the roof and held it at about 6 feet. I probably wouldn't do it now but we would run the soffit and fascia while it was suspended then lifted it to the framing. We usually did the whole house in 2 hours of crane time and saved at least 15 man days of labor.
So Rick, Let me get this straight. Are you saying that you put the plywood on before you ran the fascia and rakes? How did you do that?
Another question I have. I can't even imagine how huge a crane would have to be in order to lift an entire roof complete with shingles et al. Unless these are 24'x24' garages, how is this possible?
I'm intrigued, If this works I think it would definately be a time and money saver.
I don't know how much this one weighted, but it was a h*ll lot more than a 24*24 garage.http://www.dannylipford.com/episodes/529.htmlHere is some more information."After the roof was framed it was decked and shingled and the gable's sided windows installed, so very little work would have to be done once it was in place. The brick chimneys were even constructed on the ground (these will serve as chaseways for gas units going into the old fireplaces).The completed structure weighed 21 tons and was about 2,000 square feet at the base. A 300-ton capacity crane was called in to raise the roof the 25 or so feet from the ground to the top of the house. Internal cables supported the protruding gables during the lift, and extra blocking ensured that the roof decking stayed put as the structure flexed during movement. "
Edited 5/13/2005 12:21 am ET by Bill Hartmann
Interesting article Bill.
I'm extremely skeptical about the huge savings that they claimed.
I've prebuilt a lot of stuff on the ground but every time I analyze the idea of prebuilding roof sections, it never seems to add up to any time savings for me.
There was a guy from PA that used to build his decks, then build the roof on the deck. He'd hire a crane to come and set the roof off to the side. Then he'd build the walls. Then he'd call back the crane to set the roof on the walls. This approach makes sense to me if you have a crane onsite, but if you have to spend the extra $400 for the return trip of the crane, all cost savings are lost.
blue
In light commercial jobs, with parking-lot sized space adjacent, it often makes good sense to preassemble roof truss system sections, particularly hip ends, from the girder on out to the corners.
When I was living out in the midwest, I would see that done routinely. All you need is the space, the cribbing, and when ready, the crane.
Never saw them go up like this fully sheathed and shingled, however.
Gene, we prebuild all of our hipsets, on every job. Hipsets make financial sense to prebuild but we don't typically sheath them. Occassionally, I'll lay a sheet or two for a specific reason.
Here's a pic of a hipset that I framed on a table. It would take me another hour or so to sheath it. If I set it first on the walls, it would still take me another hour or so to sheath it. I don't see any time savings anywhere. I can lay a sheet of plywood in five minutes if it 5' high or 50 feet high. It's a wash.
blue
My understanding is, their apparent cost savings weren't only from building the roof on the ground, it was from using trusses instead of stick framing AND assembling the truss roof on the ground..
Rav, the numbers just don't add up.
The stick-by-stick reconstruction was going to cost over $200,000
The Jones' liked the idea and the fact that it would cost one-fourth to one-fifth
From a central reference point Brian made hundreds of measurements on top of the house and about as many trips down to the steel frame to lay out the roof properly.
A 300-ton capacity crane was called
The steel framework was disassembled piece by piece and removed from the house so
When you factor in all the extra work and expenses, I fail to see where the time savings are. I've framed many houses with roof lines like those in the pictures and I can assure you that it isn't possible to make up $160,000 by switching to trusses and framing it on the ground.
It is my opinion that the original house had bearing walls close enough to support a conventional roof and it would be a simple matter to re-install a conventional roof after repairing the walls. Trusses might save a day or two of labor, but they'll cost slightly more too, so the actual costs are probably within a couple of grand of each other.
I don't see a penny of labor savings by building that roof on the ground after you factor in the hundreds of trips up and down measuring, the 300 ton crane, and the erection of the staging and steelwork.
I'd bet my last milkbones that the entire basis of that story is simply hogwash.
This idea falls into the category "Just because you can, doesn't mean you should".
blue
Thanks for the replies - it sounds like such a great solution. I think I need to talk to the crane people and truss manufacturer to get lifting points. The guy I watched built false plates of 6x6 beams on cinder blocks on the ground, and built the roof on that. I'm just not sure where he tied in to lift it, or if there are plates on the bottom or top of the bottom chord of the truss.
As for weight... My trusses will be 200 lbs each, Gable trusses 345 lbs + plywood (47 lbs each), + gable overhang ladders and misc
Total truss weight (25) = 5290 lbs
Total plywood weight (64 sheets) = 2820 lbs
Plywood on gables (14 sheets) = 658 lbs
Felt Paper, Nails, Overhang Ladders, etc. ~ 500 lbs
Total 9268 lbs - not too shabby - no wonder I am so tired after truss day!