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Kwhord (Kwhord)
Senior Member
Username: Kwhord

Post Number: 307
Registered: 10-2006


Posted on Thursday, December 11, 2014 - 05:38 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

John pretty much nailed it.

Keep the sections small and put a batten and cap in with a double lock to break up the solid sections.

I can provide details to install an after-the fact expansion joint on old flat-lock with no soldering involved.

It's accomplished with a tall standing seam batten cap.
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John_chan (John_chan)
Senior Member
Username: John_chan

Post Number: 157
Registered: 08-2006
Posted on Wednesday, December 10, 2014 - 10:13 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

It's been our experience that: lack of pre-tinning, and/or torch soldering, and/or lack of expansion joints cause flat lock copper roofs to be VERY susceptible to hair line cracks after 5-15 years. We only solder with irons and pre-tinned joints with proper expansion joints now. I think that sometimes copper gets dirt/oil in between the locked panels which can lead to weak joint, and torch soldering is too hot and causes the solder to "run" and not solidify inside the joint. Obviously, lack of proper expansion joints won't allow the copper to move and causes cracks too.
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Tar_monkey (Tar_monkey)
New member
Username: Tar_monkey

Post Number: 1
Registered: 12-2014
Posted on Tuesday, December 09, 2014 - 08:41 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Hi, just went back and checked a job in lower NY that I did about 10-12yrs ago. There are now a lot of hairline cracks in the seams (about 30%).

As far as I know I did most everything right.
Used Red Rosin for a slip sheet.
Cleaned all my joints well.
Use Stay-Clean paste flux.
50-50 solder.
Used 2" cleats, 2 nails each.
Pans were traditional (pre-tinned)18x24 16oz copper.

The only issue I can see is that I used open flame to solder the seams. I've used both iron and open flame and prefer the open flame for its speed. My technique should be good, Ive never had an issue that I know of on anything other than flat lock. I know the temperate fluctuation here in the north East is crazy and was wondering if it's a problem for the copper expanding and contracting. Looking for a little more insight for some skilled roofers. Stuff like this is difficult to find discussions on. Maybe I need to get the pans tighter?...

Thanks in advance.

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