Box Gutter Fall Ratio

Flat roof design guide.

Box gutter fall ratio. There is always some confusion as to how the slope affects the overall depth. Fall gradient x distance. Minimum width 300 mm for commercial construction and 200 mm for domestic construction. Box gutters are essentially placed between parallel surfaces as in a valley between parallel roofs or at the junction of a roof and.

Box gutters allowable width slope and length. 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. Rainhead overflow or specific box gutter overflow must be at least 30mm below the height of the back of the box gutter. A box gutter internal gutter parallel gutter or trough gutter is a rain gutter on a roof usually rectangular in shape.

Box gutter with rain water head at end of box gutter. This means the downspout end of the gutter should be set 3 4 of an inch lower than the other end. Increasing the pitch increases a gutter s handling capacity but the gutter may look askew over a long run. The standard is about inch per 10 feet.

According to bs 6229 bs 8217 flat roofs should be designed with minimum falls of 1 40 to ensure a finished fall of 1 80 can be achieved allowing for any inaccuracies in the construction. This applies to general roof areas along with any internal gutters. This effectively states that all box gutters must allow for 30mm of freeboard which is from the overflow point eg. I fall or slope box gutters to be installed with a minimum uniform fall of 1 in 200 towards the outlet.

For example if you have 30 feet of guttering the calculation is 1 4 x 3 0 75 i e. Required gutter slope 1 40 to 1 200. It may be lined with epdm rubber metal asphalt or roofing felt and may be concealed behind a parapet or the eaves or in a roof valley. For example calculate the fall in a 50 metre section of foul water pipework if the gradient is to be 1 in 80.

As a general rule gutter slope is set at 1 4 inch per 10 feet of guttering. The minimal slope needed for proper gutter drainage is 1 25 cm 1 4 inch for every 3 metres 10 feet of gutter.