Gutters - how many downspouts per foot of gutter 4/12 roof


#1

We are getting ready to replace our roof and a friend looking at the gutters said we need more downspouts. Any rule of thumb on how many downspouts should be used per foot of gutter. what about problems with gutters that seem flat (no pitch away from the roof)
Roof itself is a 4/12 pitch.

Anyone know much about “leaf-guard” gutters? Good/ Bad?

thanxs :?:


#2

Normally the rule I was taught was for every 30 feet 1 2x3 downspout. Leaf guard is a style of gutter gaurds that works like a strainer. 1 draw back to it is that the little pine neddles clog them up. I am not a big fan of any gutter protection for some reason they all have a weakness. The ones that cover the top over the gutter and go up the roof in cold climates i have seen leaks in the roof from the intstallation if them. They also allow ice damning right at the eave and thats not a good thing either. Normally there is no pitch away from the gutters since it is fastened to the fascia board and that is flat off the soffit. Hope this helped if you have any other questions please feel free to drop a line. Have a great day


#3

my home is 30 x 60 a straight rectangle.

There are two 3 x 3 downspouts on it that go into pipes in the ground and out to the ditch. It works well but it is clear at times it is not enough so going to four downspouts probably 2 x 3 as they are less bulky looking. So that formula one for 30 feet makes sense.

Have needle and leaf trees tried a bunch of gutter guards and decided nothing seems to work or all have drawbacks so just keep going up and cleaning.

Is there a formula for slope when yoiu lay them out. on the 60 foot section I figured if I go high in the middle by 1/2 to 3/4 of an inch that that is enough slope? I also noticed the eves went up and down in other words they had a slope but it was pretty wonky not consistent and I want to get away from that keep it more consistent. New stuff will go on as new shingles are going on so do it all at the same time.

Warren


#4

Hi,

Do your downspouts take away the water now?

If they do then you do not need anymore.

You may cause more problems by adding downspouts. The water once on the ground may not be able to run off. Then it will go in the house.

You can just install a larger downspout. That will remove more water.

Just remember when neighbors give you this advice they will not fix it when their advice is wrong.


#5

Hi,

Gutter guards are very helpful.

If you have pine needles you will still have to clean them. Not as often.

It is easier to clean pine needles off the top of the gutter guard then from inside the gutter.

It all depends on you site to decide which gutter protection system to use.


#6

you can’t do the math like that. there is no linear foot of gutter per downspout calculation that can be made since it is the size of the area draining into that downspout that will tell you how much volume of water will typically drain through it. I’m not sure what the answer is, but I know you can’t do it per foot of gutter. I get away with my lack of knowledge on the amount of drainage by doing more downspouts and suggesting french drains on the exterior if flooded basements are a problem.


#7

but there is zero chance it will not work better with more downspouts.

The downspouts go into the ground into 4" pipe and to the ditch out front so will do the same with two more.

There is no pressure relationship like with an exhaust in a car where a certain amount of back pressure is needed or with heating ducts etc,

The biggest drawback I can see now is that the home will look a bit more clutter so maybe the two at the side back of the home should be around the back instead so only two are seen at the front.

Now that I hear that I wonder if I could put four on the back and no have any seen at all.

This would increase the capacity but the area that drains would not be from four areas on the home just the two?? Hmmm wonder about that

Warren


#8

I was taught by an old school guy i dont think it is a formula i think it is more of a guide. Im sure some math wiz could figure out the exact per foot with the water. Hey its just a rule of thumb. Not to get all upset over tho.


#9

Hi,

Here is the information you need. These are also very nice people to deal with.

http://www.gutterworks.com/Gutterchecklist.htm

http://www.gutterworks.com/hidden_hanger.html#Gutter%20Tips


#10

right on Lefty. Thanks for that link. So, 2x3 downspout can drain a 6 square roof… very interesting. Now I know.


#11

Well you learn something new everyday thanks for the tip!


#12

[quote=“pats”]We are getting ready to replace our roof and a friend looking at the gutters said we need more downspouts. Any rule of thumb on how many downspouts should be used per foot of gutter. what about problems with gutters that seem flat (no pitch away from the roof)
Roof itself is a 4/12 pitch.

Anyone know much about “leaf-guard” gutters? Good/ Bad?

thanxs :?:[/quote]

Yes, there is a method for calculating the size and quantity of downspouts needed to drain your roof properly. First, I would need to know the square footage of the roof area(s) being drained, and that includes any other roofs that drain onto the roof area where the gutters are mounted. Next, I would need to know the closest large city, so I can look into the 100-year rain storm totals. I also need to know what size gutters are installed on the building, and then I could give you a square inch total of downspouts needed. To make it easier, I also would like to know if you are using round or rectangular downspouts, and what the current size of those downspouts are.