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Gutter slope / fall - will you see it?

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We need to decide on gutter slope.
Do you slope them for avoiding pooling / performance or lay them dead flat for visual effect and to heck with avoiding pooling?
Formal tables suggest slope of 5 to 20 mm per metre for performance:
We have a "monopoly house" shape that's ~16.5 metres long. 13 metres of this is the house itself and 3 metres is an overhanging gable over a raised deck.
One downpipe each side means a gutter that is "\" shape with the pool / fall over 16.5 metres.
Two downpipes each side means a gutter that is "\/\" shape with the longest pool / fall over 6.5 metres.
Each side of the roof is ~60 m^2 in plan area. Gutters are to be 125 mm half-round in metal.
If that table is to be believed a 0.5% slope is fine for 100 mm/hour rain into one slope "\" into one downpipe.
0.5% is an 82.5 mm fall over 16.5 metres. Huge? Visible? Objectionable?
Over 6.5 metres it's 32.5 mm. Smaller. Still visible? Is "wobbly" line more or less objectionable than a straight line with bigger total fall or will you never really see the sharp corners of the "\/\" shape?
Does anybody similarly obsessive / anxious have examples of both to hand? Do you see this fall? Will you regret laying the gutters dead level?
Roof slope is 9:12 (37 degrees) and they would be positioned low enough to avoid being town off by falling snow. 
They would be the same colour (RAL 9005) as the roof / wall / fascia which should help to hide them I guess.
Other thoughts...
Originally we planned for no gutters because (1) avoids having anything that we will inevitably have to clean LOTS of leaves out of, (2) avoids anything with pooled water for the mosquitos to breed in and (3) rinses the muck off the decking.
That's not viable it turns out because (1) the one place that you don't want to end up damp (the shade under the decking) ends up the perfect shaded and damp mosquito breeding ground thanks to the runoff and (2) you get quite the splashback up the walls/windows that looks a mess even if it isn't a big problem.
Allowing the ends of the gutters to overflow on one end or fall into a hopper of some kind wouldn't be a big deal. Allowing them to overflow in occasional heavy rain wouldn't be a big deal. Don't know is this makes any difference capacity wise for having them level vs not level.
In hindsight...
I think we would have gone metal roof and had a bigger gap between the rain screen/cladding and the house (e.g. 125 mm) and hidden shutters, downpipes, etc in there where they were free to overflow without risk of damaging the house itself.
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Sound like you are a it OCD with detail as I am :)  

When I was building my posh barn/garage/shed I had same dilemma.  I ended up going for the required fall on the gutters.  Can you see the fall visually? Yes, if you look for it.  Does anyone else see that fall? No. I went for function over form.  I had black plastic gutters against dark box profile per picture below.  Not dissimilar to your property, style wise with box profile roof and sides.

I have galvanised gutters against anthracite roofline on the house.  Don’t notice the fall at all but the house is taller.  

The way I see it is the gutters are there for a reason.  Having something unlevel in my view is ok if it’s designed to be unlevel, like gutters.

Your property is beautiful.  Everyone’s eyes will be drawn to the whole building, not the gutters.  Especially if they are similar colour to the box profile.









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My roof is possibly 200 years old if the original thatch was replaced by slate in 18th century. I had the guttering renewed with the gutter clips nailed into the sarking boards under the first 2 rows of slates which were removed for nailing access and then replaced. The slope is not consistent and there was pooling. Instead of trying to fix the slope by removing the 2 rows of slates again I got round this by adding downpipes in the pooling area. 

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1 hour ago, Bozza said:

Sound like you are a it OCD with detail as I am :)  

When I was building my posh barn/garage/shed I had same dilemma.  I ended up going for the required fall on the gutters.  Can you see the fall visually? Yes, if you look for it.  Does anyone else see that fall? No. I went for function over form.  I had black plastic gutters against dark box profile per picture below.  Not dissimilar to your property, style wise with box profile roof and sides.


Thanks @Bozza


I have little visual imagination / taste myself and am more trying to avoid having to do build everything two or three times courtesy of an "eew; no; what have you done" from she who must be obeyed than I am enjoying obsessing over these details...


Your barn / garage / shed is prefect thanks. I see the fall a mile off but it doesn't look wrong. How big is it and over what distance can I ask? I'm guessing 50 mm over 10 metres on about a 3 metre high eave?



Do you have any drawings for the shed that I could pinch actually?


I will be suggesting a pure-pv roofed wriggly tin walled structure on the plot to house the pv and a lawnmower and any other treasure that I can no doubt collect once the house is finished...my suggestions for which will probably be rejected on the grounds of looks...and yours looks rather nice if I dare say so!


Pure-pv roofing meaning fitting the things as if they were regular tiles having largely setup your structure / overhang to suit the panels:









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My barn is 8m long can’t remember the fall but it was the min requirement for guttering whatever that is.  Sorry don’t have formal plans I built it by hand and within sizes that it didn’t need planning permission etc.



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For those interested:



Ruukki instructions for mounting:



Start the mounting brackets 10 cm from the edge of the run

Centre brackets spaced 30 cm either side of the "max height" in the middle

Then brackets at recommended 60 cm spacing / max 90 cm spacing (with the stronger brackets) thereafter until you hit the ends


On the slope....just 2mm per metre is their recommendation for the round bottomed gutters...but that's compensated for by suggesting a max run of 10 metres.


And stay with round bottomed gutters if possible. The square bottomed stuff is more prone to pooling. That pooled water either breeds mosquitos or freezes here. Hadn't appreciated this subtlety.



Material? Ruukki is SSAB Prelaq - 275g/m2 zinc with 35 microns greencoat RWS apparently:





So "black" probably means Nordic Night Black = RR33 / SS0015 and not quite RAL9005 of the paint. RAL9004 or RAL9005. Find out when it turns up probably.





Other brands also use the same material so probably nothing huge to choose between them other than range of accessories and stock holding




Ruukki 4 metre lengths (22 EU, 5.5EUR/metre) 


6 metre lengths allegedly available too but nobody stocks them. 


Bratex / Struga only 3 metre lengths (15.3 EUR / 5.1 EUR/metre) 






Ruukki offer a bigger range of brackets. From thin stamped ones for hot country use through adjustable angle ones to hulking great 4 mm thick jobbies:



They offer other bits like the paint and the leaf separator widget too.







Struga offerings look more basic. The option of a top restraint is interesting - mounted of the top of rafters it helps stop falling snow peeling the gutters off.










What I'd consider in hindsight is this hidden detail though. Roof ends over an "L" shaped gutter that the membrane drapes over. Then you pop a regular butter on top of that with the downpipes hidden within the wall. There's then a drip-gap between the base of the "L" and the wall in the event that the gutter is overwhelmed or blocked.



Perhaps still not a good idea still due to insects. Looks flair though. Might consider in a city environment.


That and why I didn't argue harder to fit the Ruukki roof (at 25€/m2 materials and stuff all labour vs wood) is also a consideration in hindsight. This stuff is dead easy if noisy in rain.


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Only thing that Ruukki don't seem to do is stabiliser bars for joints:







English instructions...


...say 5 mm per metre length and have a hole load more guff on safe working than the Lithuanian ones. Interesting.

Edited by markocosic
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Can I get feedback on more overthinking please?


Ho far should these sit from the (non existent) fascia / relative to the roof edge?



Option 1: place gutters 10 mm below "top" of roof covering (avoid snow ripping them off) and 10 mm set back from the "drip edge" of the roof covering nearest the wall. Shown with 30 mm total fall from highest to lowest point.





Option 2: place gutters 10 mm below "top" of roof covering (avoid snow ripping them off) and 37 mm set back from the "drip edge" of the roof covering nearest the wall. Shown again with 30 mm total fall from highest to lowest point. 37 mm was an arbitrary "looks about as much as I could get away with"





MOST of the water would run down the middle of that roof covering (the less bold line) in heavy rain.


SOME will drip off the very bottom edge. SOME may run off the top edge but that would have to be exceptional rain.



SNOW risk is pretty much all from the very top face. If you imagine a 25 mm thick clay tile with 25 mm of waviness that's about what we have.



The Ruukki guidance is silent on this positioning as their roof thickness is effectively zero. I've not found something decent yet.

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  • 1 year later...

FYI - yes you can see it at 4 mm / metre, no you don't hate it, and no it isn't enough to ensure that the gutters are dry after rain but it's probably enough to ensure that there's not enough standing water for mosquitos:








Next up...getting the heating running!





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2 hours ago, Eric said:

@markocosic gutters look fine, building looks spectacular 👌🏻

Is that larch boards? Are they stained \painted?


I'll let my wife know 😉


Rough cut pine / spruce. Graded. Grooved. Primed. Painted. Never again.


Use Ruukki roof or full-PV roof and pre-painted pre-machined thermowood boards intended for cladding and save your sanity. 😉













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