Calculate Rainwater Gutter Size

To limit the effects of thermal expansion in gutters 50 ft.

Calculate rainwater gutter size. Then use the information below to see what size gutter you need. The gutter and downspout size required is highly dependent on the amount of gutter and the spacing of the downspouts. The effective roof area that will collect the rain which will need to be removed by the guttering. If a roof s various drainage areas call for different size gutters go for the biggest one k style.

Adding additional downspouts will require less gutter and downspout volume resulting in smaller gutters downspouts. There are two things you need to know. Determine the size of your downspout. Match your downspouts to the gutter size you chose in step 7.

The area that your chosen guttering system can cope with. An inch of rain is not much but it if falls in half an hour it could flood a gutter. The downspout and gutter sizing calculator is located on the tools cad and apps page of the smacna website. 15 m is a practical maximum gutter length to be served by a downspout.

6 inch 7 960 square feet. The total rainfall and how rapidly it falls will affect the runoff from the roof. Refer to the gutter packaging or specification for the recommended downspout size. Multiply the drainage area by the roof pitch factor and rainfall intensity to find out the adjusted square footage.

This can be calculated by using the following formula see diagram below. If a roof s various drainage areas call for different size gutters go for the biggest one k style. Calculating effective roof areas where gutter angles are installed effect of angles if a length of eaves gutter includes an angle. Calculations are based on level gutter capacity as experimentally determined by the national institute of standards and technology nist.

As most roofs are not flat this needs to be calculated we ll show you a simple way. Then use the chart below to see what size gutter you need. 5 inch 5 520 square feet. 5 inch 5 520 square feet.

Rainwater calculations on face value guttering installation is a piece of cake but it is amazing how many installers get it wrong. Total roof area also affects runoff. The simple way to calculate gutter sizes. Please lower the maximum spacing between downspouts to see this effect.

Box gutter with rain water head at end of box gutter. Simplified suitable for flattish roofs with little or no vertical faces or steep roofs draining to one side of box gutter only or any roof if you are in a hurry and make the necessary allowances for all catchments. Multiply the drainage area by the roof pitch factor and rainfall intensity to find out the adjusted square footage. Downspout sizes must not exceed the bottom width of the gutter.