I currently only have gutters on the front and back of my house. I'm wanting to put gutters on the other 2 sides now (see orange highlighted sides) for various drainage reasons.

I have 6 existing 2"x3" downspouts on the existing gutters in front and back (see red circles). The contractor I am leaning towards stated I don't have to put additional downspouts on the new gutters if I increase the 4 downspouts in the corners from 2"x3" to 3"x4" (see larger orange circles). He plans on tying the new gutters into the existing gutters so the gutter system will be connected all around the house. Putting additional downspouts on the new gutter's center would not look good and cause big mud pits in the center.

Would increasing the 4 downspouts in the corners from 2"x3" to 3"x4" provide enough drainage for the new gutters? Most Google searches stated you need a downspout every 30'-40'. The 2 new gutters on the sides of my house would be 56' and 66'.

I've upgraded downspouts from 2"x3" to 3"x4" and it made a huge difference. It basically doubles the opening's flow rate.

Gutters are something I don't generally comment on as it's out of my realm of expertise but the slopes of the roofing draining into those gutters will also matter.


I agree with the above. I think you'll be fine. I think increasing the existing downspouts will provide suitable drainage. My gutter runs aren't quite as long as yours but they are at least 40' feet and I have two downspouts on those runs like your drawing. Just make sure they arch those gutters and pitch them evenly so you have a balanced flow on each end. Mine aren't quite perfect so one end has more water than the other.

Can you do them as he suggests but make the deal with him that he'll add more if it doesn't perform well?