Gutter layout and sizing

A gutter should be laid with a slight fall towards the outlet. Where the outlet is not at the end, the gutter should be sized for the larger of the areas draining into it. The gutter should be laid or constructed so that any overflow will discharge clear of the building. The flow capacity of a gutter is dependent upon its cross sectional area, length, bends (if any) and the shape of the outlet. Table 4.3 gives the maximum effective areas which can be drained into the common sizes of true half round eaves gutters with sharp edged outlets. The Table also gives the minimum sizes of outlets which should be used with the gutters and the flow capacities for use with paragraph 4.6.