Hello,

An illustration at the top of page 15 here shows the brim of the Lindab gutter 25 mm below the roof line.
https://europeangutters.ca/wp-content/uploads/2024/08/Lindab_assembly_rainwatersystem_EN.pdf

 

That's only to prevent water overshooting the gutter; correct? Any harm if the distance is less than 25 mm?  Ventilation of the fascia reduced?  Hypothetically the distance can be zero or negative depending upon roof slope, gutter width and height of the gutter.

 

This roof is 1:3 pitch, asphalt shingled.  The rough surface allows slower runoff than steel. Water is unlikely to overshoot the gutter even where clearance is more than 25 mm.

 

Thanks,             ... Peter E.
 

Looks like you have identified all the issues and I can't see any reason why it cannot go higher. 

15 hours ago, peasthope said:

....

That's only to prevent water overshooting the gutter; correct? Any harm if the distance is less than 25 mm? 

...

 

Are Lindab's assumptions the same as yours?  (Page 4)

 

'...Lindab has used the Swedish standard with a rainfall volume of 0.013 l/sqm...'

 

and further 

 

'... It is difficult to generalise when it comes to the design and dimensioning of roof drainage, even though there are industry standards to rely on. In recent years, we have seen that rain volumes increase in certain rainy periods and, above all, that the intensity of rain showers has increased both in terms of time and quantity. Adjacent topography, other buildings and the building’s design can also influence the needs of the building in question. Combined, these factors mean that a property owner should - in addition to industry requirements - take into account the building’s needs and vulnerability...'

 

When it rains in BC, man does it it rain. Might you have generalised rainfall reference tables for your area?

Edited October 2Oct 2 by ToughButterCup

I agree with MikeSharp01 that you can go a bit higher, especially on a shingled roof where the water runs off more slowly. The thing I would watch is not letting the back of the gutter sit so high that water runs behind it and down the fascia in a heavy downpour. Keep a clear drop into the gutter and a steady fall along the run, and check it in the first proper rain before you call it done.