There is an interesting phenomenon which occurs with certain types of rain.
This phenomenon leads to phone calls which we field from concerned people that believe that their gutter system is not large enough to catch the water that is coming down their roof in these rain events.
In observing the rain coming down the roof, the water appears to ‘overflow’ the existing gutter system, leading to the idea that one may have that their gutter system is simply not ‘big’ enough to accommodate the amount of water coming off their roof with these types of storms.
While this is certainly a valid thought given what the person is most likely observing as the water is coming off their roof, what is a fairly frequent response from my end is that a new, “larger” gutter system is very much NOT needed.
The standard gutter system that the vast majority of folks have on their home is a 5” gutter system.
When asking to enlarge their gutter system, the gutter system that the concerned caller on the other side of the phone often references is the type that they see on commercial buildings – a 6” gutter.
The thought process logically being that the larger gutter system will be able to catch the overflowing water which their existing gutter system so often appears to be subjected to.
The challenge is, and I always explain this, is that the water is not really ‘overflowing’ their existing system at all.
Instead, the water is actually ‘jumping’ OVER their gutter system.
What occurs in these rain events, and there definitely is a threshold somewhere that has everything in terms of water below it flowing ‘into’ the gutter system, and everything above that definitive volume of water jumping ‘over’ the gutter system.
What happens is that when the amount of water that is falling during a given storm matches a certain point with the area of roof that it is hitting, in combination with the pitch of the roof, the roof essentially turns into a type of ‘ramp’ – think BMX bike ramp or Monster Truck jumping over cars ‘ramp’; when the perfect combination of volume of water & speed coming down the roof is met, as the water hits the edge of the roof right BEFORE the gutter, the water ‘jumps’ over the gutter and provides the appearance of overflowing it.
I am sure there is some type of physics equation somewhere that can illustrate this from a scientific standpoint much more eloquently that I do.
Though fancy formula or no fancy formula, the result is the same and although one may initially think that simply increasing the size of the gutter will help better ‘catch’ the water coming off the home, this is just not scientifically feasible to do with standard gutter systems.
Even if commercial gutters are installed, the realized benefit will be minimal as with that certain volume of water, the water will most likely jump over the larger gutter option as well.
It would be an expensive experiment to change out all one’s gutters in the hope that the upgrade to the larger system will catch what is coming off the roof in a significantly better fashion than their traditional gutter system.
While there is no 100% surefire way to put a gutter system in place to truly combat these types of situations, it is important to realize that the larger the roof and the greater the pitch, the more difficult it will be to catch rainwater in the gutter system and funnel it away from the house in larger rainstorms.
There is absolutely still value in having standard gutters on our homes, the proper expectation should be set however, that with certain rainstorms, the gutter itself will not be able to catch ALL the water as it comes off the house as ideally as one would prefer and simply enlarging the existing gutter system will not necessarily provide the fix that it may initially seem like it might.
