On Sat, 30 Jan 2016 23:09:43 -0500, wrote:

As far as aluminum, it will expand much faster than steel from ice. One
thing evryone seems to ignore is that it's not just a small puddle, it's
a spot that attracts debris, and that freezes and adds more ice and then
there are ice dams.... Heck, I've seen small trees growing in gutters if
people dont clean them.

That has nothing to do with the slope though.
As for the cost of seamless, I had mine installed for what it would
have cost me to buy the steeland pay myself 50 cents an hour to
install it - it was a total no-brainer. I could have done it in Platmo
or some other DIY plastic for less - but that stuff is all junk up
here in ice and snow country.
I put gutter guard on all of mine so I don't have to climb up and
clean the gutters every year.

Actually it has a LOT to do with the pitch. Debris flows out of a gutter
that has more pitch, than on with little pitch. Sure, no amount of pitch
will stop all debris, but more pitch helps.

I agree about those plastic gutters being junk. I put a short 6' section
over the door on my workshop and after one winter it was broken apart.
But it was a scrap piece that was given to me, so I'm glad I found out
how bad the stuff is without spending any money. I replaced it with some
used steel gutter I also got for free. That works fine.

Gutter guards would not work good on my barn. That barn roof collects
debris on the roof itself. The roof should have more pitch, but it came
with my farm, so I had no say in the matter. I have to sweep leaves and
fallen tree branches at least twice a year. But it's flat enough to
easily walk on it and clean the gutters from on the roof.