O/T: Designing a Gutter System For the House

I have a two-story home, about 40 x 34, plus two porches. Three sides of the house have sidewalks and a level grade away from the house. The back of the house has no sidewalk, and the ground slopes away from the house, so I would like to only put downspouts in the back of the house, if possible. Right now, the place just has gutters over the entryways, but I’d like to put them around the whole house to help keep the basement dry.

I’ve heard a couple of rules of thumb so far, i.e. slope 1 inch for every 40 ft of gutter, but I’ve still got a ton of questions. Like, can I get away with just two downspouts, or do I need more? How big of downspouts do I need to handle the roof area? Is it OK to let water drip from the main roof down to the patio roof and then into the gutter? Etc.

I was hoping to find one website or one book that would cover everything about placing gutters.

Any ideas?

About the only place I know of that will have this info is the SMWNCA, Sheet Metal Workers National Contractors Assc, and they won"t give out that info to just anyone. As the name says, the info is for SM contractors.

I do have a condensed copy of the info. I need where you live (nearest major city) and roof square footage, then I can tell you whats recomended for your area.

T_Bone

I'm still kinda new at all this. What's a drip line? What kind of tile? What's the footing level?

Where you are/rainfall, average temps will determine how far apart your downspouts will need to be. Overloading a gutter/downspout is worse than not having any at all. Dropping off one roof to run down another to a gutter is perfectly acceptable and just makes good sense. SMACNA is a good start for standards in sheetmetal design and practices. ANY of the local union shops or even the local library will have this info on hand. Remember, if your locale gets into extreme temp swings between hi and lo, you also need to consider the length of the run in regards to expansion(side movement) as WELL as it's ability to adequately drain off the heaviest expected rainfall in relation to the square area draining into any run. Code here is 1 downspout per 40ft of run on residential sizes and 50ft on commercial. OUR shop's reputation demands 30 and 40. REGULAR cleaning is a must. HTH jim