Just having a new roof (not diy sadly!) and the scaffolders came
yesterday, so I couldn't resist hopping up to take a proper look
(actually, I had to because they had disconnected a downpipe !) Now,
I was planning to exploit the scaffolding to replace the guttering
once the roof is done and have been cogitating on whether to use round
or square. I had sort of decided to use round as, although it doesn't
look as good, the idea that flows are faster than in a flat bottom and
so flush the silt out sounds compelling. My roof has quite a shallow
pitch, so tends to form moss, so that may be more of an issue than
silt.

Anyway.....Once I got up there, my existing round guttering was
absolutely chocka with goo, moss and silt while my neighbour's, which
is a square jobbie, was completely clear. Since they were both last
cleaned out at the same time (couple of years ago) this seems
completely against the theory.

Does anyone else have a similar comparison? I guess her gutter might
have a better fall in it than mine (although there's precious little
space for either) but I wonder if, somehow, moss and silt behave
differently in the two different profiles.

On Aug 5, 11:41 am, GMM wrote:
Just having a new roof (not diy sadly!) and the scaffolders came
yesterday, so I couldn't resist hopping up to take a proper look
(actually, I had to because they had disconnected a downpipe !) Now,
I was planning to exploit the scaffolding to replace the guttering
once the roof is done and have been cogitating on whether to use round
or square. I had sort of decided to use round as, although it doesn't
look as good, the idea that flows are faster than in a flat bottom and
so flush the silt out sounds compelling. My roof has quite a shallow
pitch, so tends to form moss, so that may be more of an issue than
silt.

Anyway.....Once I got up there, my existing round guttering was
absolutely chocka with goo, moss and silt while my neighbour's, which
is a square jobbie, was completely clear. Since they were both last
cleaned out at the same time (couple of years ago) this seems
completely against the theory.
Is her roof facing in the same direction (N, S, E, W, etc), along the
front/back of a terrace, or is her's in the opposite direction? Could
make a difference to the amount of rain and/or moss on her roof.

Also, is the roof made of the same material? If yours is shedding
lots of grit, but all that comes of hers is water, that would make a
difference?

Both houses are parallel and face south east at the back and north
west at the front. THere are no trees overhanging either and we have
similar amounts of moss on each roof. The roofer tells me that the
moss is the result of having sanded tiles on a shallow pitch and
they're about to be replaced with smooth tiles (not for the moss, but
because they've begun to crumble and leak).
So for all practical purposes, the two houses are identical, the only
differences that I can discern being the profile of the gutter and yet
the outcome seems to be the opposite of what may be expected.
As far as I'm concerned, it's fine, as it indicates that the square
gutter (which suits the house better) is not such a bad thing,
although Sod's Law might come into play once the tiles have been
replaced and the moss is no longer a serious problem.

On Aug 5, 4:57*pm, GMM wrote:
Both houses are parallel and face south east at the back and north
west at the front. *THere are no trees overhanging either and we have
similar amounts of moss on each roof. *The roofer tells me that the
moss is the result of having sanded tiles on a shallow pitch and
they're about to be replaced with smooth tiles (not for the moss, but
because they've begun to crumble and leak).
So for all practical purposes, the two houses are identical, the only
differences that I can discern being the profile of the gutter and yet
the outcome seems to be the opposite of what may be expected.
As far as I'm concerned, it's fine, as it indicates that the square
gutter (which suits the house better) is not such a bad thing,
although Sod's Law might come into play once the tiles have been
replaced and the moss is no longer a serious problem.

Is hers set at a steeper angle relative to the ground and thus giving
a faster flow?

Is hers set at a steeper angle relative to the ground and thus giving
a faster flow?

They look about the same to me: There's next to no space for a
serious fall on these houses, so neither of them is very steep.