Closest I can come is I built two of 'em on-site, but didn't cut the roof out (from the attic) 'till they were weather-proofed. I pre-drilled 4 locator holes for each, - - then went to town. They were 5'4" wide.

I think building them off-site should work out fine, - - just make sure you get the 'mean average' of the slope of the roof for all four, - - then you can shim a little here and there for any variations on each once you're ready for 'install'. Or if the roof really varies and you want to get particular you could leave the sheathing run a little 'wild' on the bottoms, acting as a scribe.

I think if I were doing it, - - I'd build them as just 'wall systems' for ease of transporting/lifting. Unless you've got some equipment to get 'em up there.

 

On this particular job machinery is'nt a problem, hell with the toys he has on hand we could lift the house-literally:w00t:

 

Go for it Josh..... Shouldn't be any problem at all:thumbup:

I built a chimney chase a few years back, about 14' tall. I did it on the ground because the specs on the woodburner recommended Durock lined on the inside. So this thing was heavy. I didn't want to lug all that durock up on the roof.

Last year I built a "steeple" for on top of a turret on a customers house. Did that on the ground, shingles and all. That was 12' X 12' X16' tall.

Make sure you have solid fastening on the existing roof. Don't just depend on the roof sheathing and some screws to hold them.

 

Got a customer that wants 4 dormers installed on his story and a half, nothing big-4' wide, mainly just wants added natural light in the small attic space where his little office is at. Currently he's gotta get a new roof since it's falling aprat and has zero roof vents....you read that right zero vents. He has intake on both side of home for knee walls and one on each side of tiny gable peak above the attic ceiling but that is it.

Anyways, was thinking to increase productivity with jigs and multiple assemblies building the basic structures off site so when we get there it's a fast transition to set them and blend in since rain seems to be the story of the day round here this year. Has anybody done this? I'm trying to talk him into gutting the attic before we do the dormer installs since he wants it all refinished anyways and currently it's all car siding on walls and ceiling=PITA for demo I'm not looking forward to and he likes trying to save a buck too.

Lemme know about your expriences.

You can prebuild anything. Once you have the existing roof pitch your on your way. What are you going to do about doubling up the rafters for the dormer walls to sit on and installing a header or true valleys?

 

Wow measure 40 times and cut once. I would think there are far too many variables that need to be accounted for in the field. Keep in mind we've only done a few dormers, but in my imagination, I couldn't see how we could get everything to exactly match up and just hoist and fasten.

If you can, you are much much much better than me!

 

Grump: the roof pitch will be the same on both sides-simple story and a half so once the angle is figured out it's just simple math deducting for wall studs. Like some of the stuff I'll build a jig at the homes roof angle to be sure the first templates match up exactly and after the first one is done we'll have all the mesurements for the last 3 so they should go pretty quickly. Then it's just a matter of loading on the trailer and setting into place with the equipment he has at his place. I'll forgo siding and shingles unit they're set in place since I know I'm not that lucky or as good as design homes LOL!! so we'll just set the framed e walls and roof then hand frame remaing roof to tie into existing roof.

Joe: initally the plan was to re-roof the entire house and tear out sheeting, reframe dormer area's then re sheet. Recent hail storm tore his place up and he's lost portions of his bathroom ceiling and a small area in kitchen so he'd going to re-roof the place now to save on future damages then we'll just have to cut in/tie in like any other job. not the ideal situation, but it is what it is. Planning on using LVL's for sister rafters as well as headers, plus we're only going 4' wide so these dormers are not big by any standards so ultimately I think it'll be framed stronger than it needs to be. As far as fastening we'll tack them in place with framing nails and I was planning on main attachments being 4" lags 16" oc in addition to framing nails so I think that is more than enough to keep it in place?? since most of the older dormers we've worked on were just nailed only. Basic dimensions are 4' wide and exterior end wall will be approx 5-6', just enough for a small window to let in light...fancy skylights is all these are going to amount to. Inital plan/idea was a dormer the full length of the home, but after talking with a designer/engineer that idea was quickly scrapped once I explained the entire roof and gable end walls would have to be removed, new ridge beam supports to footing depth installed, etc...not in the budget he says so he just wants baby dormers.

 

I've done this before and you have to be careful, 99% of the time it will go off without a hitch, it's that 1% you have to watch out for. If your working on a house that has settled in an uneven way you might find that you have to rack (tweak) the dormer to seat properly, and if you have it sheathed this isn't so easy. You may also find that widow(s) wont fit if you framed the openings tight or that the window won't fit flush (a corner sticking out from racking or shiming the dormer). After that experience I use a string line and or laser to make the measurements from and put any of the sheathing on after the dormers is up. You might also find that each of the four dormers is a little different in size from side to side if you are going for level and not matching what's existing. Pre-fabbing the dormers is a great idea only if you don't have to do a lot of work to fit them, lots of measuring and some templates will definitely help.

Kevin

 

I dunno, you have to know exact angles of the roof because if you are off 1 degree so will your walls... Is it possible? I am sure it is. However I feel like it is easier to do a good job if built, not only on site, but on the spot.

Personally I wouldn't even consider it an option. Maybe only because I am not skilled enough in this area or expertise, but as you know by now I employ the "better safe than sorry" scenario and walk away froom jobs I am not 100% sure I can pull off without a hitch. I save the gambling for the river boats.

 

I employ the "better safe than sorry" scenario and walk away froom jobs I am not 100% sure I can pull off without a hitch. I save the gambling for the river boats.

I agree to a point, and I like a safety blanket too, but I'm a adventurious SOB and hate being stuck in the same rut so if it's 50% out of my comfort zone, I'm all over it. Otherwise you'd never learn anything...but that's not always a bad thing either doing the same repetative job like a factory...just not me.

Before any material is bought I will get my numbers off the roof and make it happen, it will save time in the big picture vs focking around per dormer on site, that way when we show up to install we cut our screwing around time in half as well as opened up roof time...I tried pushing for a whole second story, and am glad we did'nt do it thus far with the friggin rain we've been having this year, but would still rather see him do a true 2nd floor than add these goofy little dormers and then do the addition to the side of his house next year...the full 2nd story would be much more user friendly.

I've seen valley truss kits off more than 1* and they still worked-not the technical same, but jobs always have a degree of err in them depending on work being done....waiting for the high horses to get saddled up now...:whistling :laughing:

 

Ok I used 1* as an arbitrary number to make a point. I know 1* doesn't matter much, however the point is still valid, it'd be easy to mess the whole thing up. Measure 40 times and cut once. Good Luck!

 

I'm confident it will work just fine Josh... But if you have any concerns, try this.......Find a big piece of rigid cardboard or even 1/4" masonite, and cut to the angle of the roof. Use this as a template for checking all four areas of the new dormers. Take a level up with you and check for plumb and level. Basically you would be making a template of one dormer side.

If any of them are off a little, make notes on the template as to which ones need adjusting. But like others have said... a little shimming here & there is prolly all that will be needed.

 

Should be gravy Josh. You may have to rack them a bit if the pitch doesn't match up exact, but that's just a matter of checking it before you build. Don't know how you're tieing in the ridge, but you may want to let that run wild in the case you have to rack it. Only person that would see the racking is the drywall guy. Not a biggie.

 

The ridge will be tied in last as far as securing goes so that way if I have to rack the dormer body a touch to square it or make adjustiments to match existing I can do it easily, otherwise I'd be screwed LOL!!

Grump, I know the 1* was a example, but unless budget and time is truely not a concern making everything PERFECT on a house that is 50-60yrs old will not happen, you can make it as close to perfect as possbile but anybody that's done extensive remodeling knows there is a place lines have to be drawn or else you'd have to tear down the entire house. I'm sure we'll have to tweak/shim etc... since we'll build for perfection and have to match upto aged. Even building on site at each of the 4 locations would be entail compromises at some point. Guess I'll have to buy a truck load of caulk to make it right:w00t: :w00t: :laughing: Maybe we'll install them severly crooked and put on a hip hop homes for sale website

 

I agree, go for it!

 

Josh,
In my other life when I had my framing Co. we did a Colonial Strip Mall. One of the buildings had 20 dormers around it ( approx. 4 footers in width ) anyways what I had the crew on that job do was make a 6' wide mock up section of roof on the ground to the exact roof pitch long enough to build the hold dormer with ridge , valleys , trimed them all out even set the windows in them. You just want to make sure you take the time to get that roof section level side to side and the pitch right on. Tack your bottom plates on the roof deck and go at it. I had 3 men working on them, 1 cutting and 2 assembling them. We just found a balance point and attached a nylon strap to the ridge and lifted them into place with a Lull w/ a jib on it. Working and doing everything at ground level you can really make good time. Wouldn't even think twice about doing it this way. The Modulars we do now the dormers come out of the factory complete all shingled, all you have to do is release the Ice and water shield for the valleys and tie the shingle to the main roof in to them. Good luck and post some pics.

 

Joe, excellent advise and thanks to all that have been there done that, now it's just a mater of doing it when this job get's scheduled:clap:

 

I know this is long since done - but I agree with others - you CAN offsite prebuild everything.

Built this in Clarksville, TN then trucked and installed it in Pleasantview, TN