Proper Gutter And Downspout Sizing

Increase the pitch of the gutter.

Proper gutter and downspout sizing.

Now architects engineers designers and contractors can easily and accurately size downspouts and gutters according to the specifications in smacna s architectural sheet metal manual 7th edition 2012. Increase the pitch of the gutter. To properly size gutters for installation you need to know the local rainfall intensity. The saf perimeter systems gutter downspout capacity table click to enlarge relates downspout size to gutter sizes.

For most homes 5 inch or 6 inch gutters are sufficient although the number of diverters and downspouts will vary. The standard is about inch per 10 feet. Allowance per square inch of downspout for 1 in hr 25. Downspout sizing in sizing downspouts the following considerations apply.

Downspouts of less than 7 00 sq in 4515 sq mm cross section should not be used except for small areas such as porches and canopies. Increasing the pitch increases a gutter s. Water capacity values of a gutter downspout system is calculated using the height head of water a gutter can hold the outlet orifice size of the downspout and the quantity of downspouts used. Get 7 or 8 inch gutters.

Gutter dimensions are selected from the horizontal gutter sizing table based on the slope of the gutter to the downspout s and the gutter capacity based upon the roof flow rate in gallons per minute. They ll cost more and probably require a custom order through a professional installer. The size of the downspout should be constant through out its length. Get 7 or 8 inch gutters.

You have three options. The standard is about inch per 10 feet. Are sized in relation to rainfall on this basis. The second most common style of downspouts in urban homes is the rectangular downspout coming under a range of sizes such as 2 3 3 4 and 4 5.

This type of down spout is considered the standard downspout style in households and is used with a 5 k style guttering system. It also comes in sizes 2 3 and 3 4. The downspout and gutter sizing calculator is located on the tools cad and apps page of the smacna website. The gutter and downspout size required is highly dependent on the amount of gutter and the spacing of the downspouts.

Increasing the pitch increases a gutter s. Adding additional downspouts will require less gutter and downspout volume resulting in smaller gutters downspouts. A professional gutter installer will take all these measurements into consideration and determine the proper size gutters for your home. You have three options.

Mm hr rainfall that varies with diameter for example 3. Area for drainage design and they often use a square foot. Plumbing codes typically use the vertically projected roof. Downspouts should be constructed with conductor.