Box Gutter Overflow Design

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Box gutter overflow design.

A good box gutter design will have falls along its length together with sumps to collect water before it is fed into large downpipes. A box gutter is defined as a graded channel generally of a rectangular shape for the conveyance of rainwater within the building footprint including adjacent to a wall or parapet. Failing to install appropriately designed box gutters and correctly sized and positioned overflow devices can lead to serious damage to buildings and contents especially in shed and flat house roof designs often resulting in hefty insurance claims which are a total burden. A wider overflow needs less depth of overflow hence the box gutter depth will also be reduced.

There will also be an overflow facility on the side or the end. Drill rivet holes for the gutter splash guard. You can find these precut gutter splash guards about 3 in brown and white aluminum at a home center but you could easily make your own out of aluminum or sheet metal and spray paint them to match your gutters. The box gutter depth and the sump length are influenced by the size of the overflow.

This is very important so that water will overflow externally to the building rather than flood into the roof cavity. However a wider overflow may increase the length of the sump. A rainhead or sump is a container located between the gutter and downpipe that aids the flow of water away from the roof. The hydraulic capacity of the overflow device must be no less than the design flow for the associated box gutter outlet.

Overflow devices shall discharge to the atmosphere. Rainheads are an essential design element for buildings where internal box or trough gutters are used. To use the gdo calculator enter information about the location roof design and types of overflow measures. Making the box gutter wider will also reduce the box gutter depth.

The hydraulic capacity of an overflow device shall be not less than the design flow for the associated gutter outlet. The gutters downpipes and overflow gdo calculator assists in developing a better understanding of the ncc volume two part 3 5 3 gutters and downpipes acceptable construction practice acp provisions.