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-   -   bay window roofs (http://www.sheetmetaltalk.com/showthread.php?t=2150)

Guttermonkey 09-11-2011 12:00 AM

bay window roofs
 
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Here's a couple bay window roofs we did about a month ago. I did another last week and the homeowner didn't like that the ribs had so many crimp marks so I'm having some battens machined up to fit over. Hrmm.

roofermarc 01-16-2012 08:25 AM

1 Attachment(s)
Quote:

Originally Posted by Guttermonkey (Post 13885)
Here's a couple bay window roofs we did about a month ago. I did another last week and the homeowner didn't like that the ribs had so many crimp marks so I'm having some battens machined up to fit over. Hrmm.

I wonder who ever came up with this style of hood roof. If I get my distance up and distance out, scribe a radius or curve, step off the curve in equal distances, draw a 22 1/2 % line and plot the points onto the s/o, I'm left with my pattern that is narrower at the top and wider at the bottom. The technique displayed here had to be done to skip the layout process. Not trying to bad mouth anybody's work, but I just don't think its right. Here,s another pic of what I'm talking about. To the untrained eye it would go unnoticed.

Guttermonkey 01-16-2012 08:54 AM

Hey, Can you explain in a little more detail? We do a bunch of these and I like to hear how other people are doing them.

Thanks,

John

smwlocal24 01-20-2012 06:03 PM

Quote:

Originally Posted by roofermarc (Post 14257)
I wonder who ever came up with this style of hood roof. If I get my distance up and distance out, scribe a radius or curve, step off the curve in equal distances, draw a 22 1/2 % line and plot the points onto the s/o, I'm left with my pattern that is narrower at the top and wider at the bottom. The technique displayed here had to be done to skip the layout process. Not trying to bad mouth anybody's work, but I just don't think its right. Here,s another pic of what I'm talking about. To the untrained eye it would go unnoticed.

There would still be about the same amount of layout; the layout is just different. This other style would require the middle section's curvature to be elliptical and the curvature of the corner sections would have to be circular. With this other style the total mitre angle is "cut" into the corner sections' hip panels.

With the style you prefer, all three sections are circular curves and the mitre angle is split between the hip panels of the corner and middle sections. I too prefer the same style you do because it looks better when all the sections have the same curvature. However we usually don't get to build the structures we work on which pretty much governs what type of layout is required.

roofermarc 01-21-2012 06:30 AM

sweep roofs
 
These roofs are hollow, there not framed.

smwlocal24 01-21-2012 09:05 AM

Quote:

Originally Posted by roofermarc (Post 14286)
These roofs are hollow, there not framed.

Oh, well then I suppose a guy could do whatever he wanted to do. The ones that I have done were always framed and sheeted, and were re-roofs so I would have to select curvatures that would work out with the existing structure and I would have to install flashings that would cover up any previous bad cuts into the bricks and mortar. It would certainly be easier to build a freestanding roof without having to worry about the extra constraints of a roof structure. By looking at the pictures of Guttermonkey's roofs, you can tell that his roofs had a structure to match up to as well; the one picture has the last panel missing and you can see the structure below with rosin paper on it.

roofermarc 01-22-2012 10:07 AM

Yeah, I see that rosin paper and the deck now, and we were told yrs. ago not to use rosin under copper! I forgot why though. You would have no layout on these as you have the measurements given to you already, just add a little to make sure it would fit over. Actually a real time saver and a more solid and waterproofing means. I like the frame technique now.

smwlocal24 01-22-2012 02:08 PM

Rosin paper only needs to be used under copper when soldering in order to prevent damage to the underlayment from the high heat of the iron. Without the rosin paper the underlayment could melt and seep into the solder joints thus contaminating them.

I would argue that there is more layout involved when there is a structure present. Having a structure present results in more measurements to measure, which results in more contstraints. Without having a structure, one could build the panels any way they wanted to as long as they matched up with the top edge of the window and intersected with the brick wall somewhere. I suppose a guy with little sheet metal layout experience could use some cardboard or paper and lay it on the surface as long as it was a calm enough day and make patterns, but that wouldn't be any faster than layout especially if someone has access to a plasma table or is good with layout. Regardless of the technique of pattern development used, the time to make the pieces should be the same. However, with a roof structure present any error could result in the panels not working out where some errors might not matter without a structure present.

There is also the issue of measuring the curvature of the roof structure which would not be necessary without a governing structure. While this is not that tedious in nature, the production of the same curvatures on the panels can be, and again if the curvature was wrong on the panels produced the structure could interfere with them causing kinks or buckling in the surfaces and seams of the panels. Without a structure there it would not matter what curvature is used.

ifishalot7 01-27-2012 09:42 AM

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I thought the purpose of the rosin paper was to be a barrier to keep the the copper from reacting with the asphalt underlayment.I started using it on my jobs for that reason.I personally prefer a substructure.It is much more substantial and gives you something to fasten to,cuts down on noise and cushions against hail.In my experience the lay out is less time consuming with the structure as well.The problem that arises though is when the builder doesn,t take the care to provide a clean and true surface to attach your work to or doesn,t know how to make a proper curve or arch.Here is an example of what I am talking about.Notice how the top is arched but the sides are basically flat.It wouldn,t be so bad if I hadn,t prebuilt and preformed everything prior to arriving at the job based on given diminsions.After all the extra work it caused me,we had a basic geometry lesson on how to bisect a chord find a point and swing an arc.

DennisM 01-27-2012 04:27 PM

You're both right. Rosin paper protects from tar seeping into the joint, reacting with the copper (minimal problem) and also keeps the copper from sticking to the tarpaper. Allowing the copper to expand and contract.
All our copper roofs are laid out and mostly cut in the field. Seems most builders have a hard time keeping all the sides the same size.


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