Gutters and downspouts

[William M. Corbett]

Does anyone have a good rule of thumb for distance between downspouts?
I am at an inspection (new construction) with a roof pitch of 12/12 and there is a distance of about 100 feet between downspouts.

[Bruce M. Graham, III]

I think that they recommend a down spout every 30 ft.

[William M. Corbett]

That's what I thought as well, but this is the third new construction house I've seen like this in a month.

[ekartal6]

I believe distance between downspouts may be subject to local ordinance, but don't quote me.

[afrost]

Originally Posted by wcorbett

Does anyone have a good rule of thumb for distance between downspouts?
I am at an inspection (new construction) with a roof pitch of 12/12 and there is a distance of about 100 feet between downspouts.

depends on how much roof surface it's serving.
i think i read 1 rainleader per square of roofing

[Marcel R. Cyr]

This might help.


http://www.copper.org/applications/a...uts/intro.html

Marcel

[Carl Brown]

William,

Did they have kickout diverters?

[William M. Corbett]

No, no kickouts. I would also think the roof surface area would play a part in the amount of downspouts.

[Ed Fako]

The correct answer per SMACNA is typically 40 feet maximum distance. This is assuming a 2" x 3" downspout leader pipe. The rain tables in the SMACNA manual also would further weigh on the distance.

Ed

[dchew]

A lot of new construction in my area has the upper roof downspouts spilling onto the lower roof and then into the lower gutters. Use some common sense when making this type of determination. There may be no definite rule to go by.

There's nothing more stupid than 1/2 of a roof over a 2 story, 3000 sf house that has to drain everything through 2 downspouts. Poor design, poor installation.

[Larry D. Kage]

Originally Posted by dchew

A lot of new construction in my area has the upper roof downspouts spilling onto the lower roof and then into the lower gutters.

On asphalt shingles especially, that practice will cause premature wear where the concentrated water load is on the lower roof.

[Terry Neyedli]

Originally Posted by wcorbett

Does anyone have a good rule of thumb for distance between downspouts?
I am at an inspection (new construction) with a roof pitch of 12/12 and there is a distance of about 100 feet between downspouts.

In our neck of the woods I was taught to go by the rule of 20-25 feet for a 4" gutter and 30-35 feet for a 5" gutter system. Seems reasonable to me.

We are very close to as area of Vancouver Island known to have one of the highest rainfalls in North America, 27 feet per year (Kildonan, B.C.).

T.Neyedli
www.alphahomeinspections.ca

[Rick Maday]

Originally Posted by wcorbett

That's what I thought as well, but this is the third new construction house I've seen like this in a month.

Is it "right" because everyone is doing it?
I believe a D/S for every 40 ft of gutter is recommended. It may be worth a call to the builder(s) and ask them why.

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[Brian E. Kelly]

Interesting thread, below is my standard gutter comment.

There are no gutters on the residence, which is common in Arizona. If drainage is a problem you may wish to add gutters.

[Ed Fako]

Here is a link from pathnet regarding this topic.

CHAPTER 4 - Rain and Water Vapor


Ed