Guttercrest

Guttercrest Rainwater Calculator

Enter the property's postcode and the dimensions of the roof section draining into one gutter.

1

Property location

We will use this location to select the regional two-minute design rainfall rate.

2

Roof dimensions

Measure the roof section that drains into this gutter.

Roof type
metres
metres
degrees

Enter only the rectangular roof section that drains into this gutter.

Common pitches:
3

Gutter and outlet selection

Choose the gutter family and outlet arrangement. The calculator will recommend the smallest suitable profile and outlet.

Position affects both the flow per outlet and the maximum hydraulic length.
This controls the outlet coefficient separately from a general leaf guard.
4

Roof-water capture check

Check whether water leaving the roof is likely to land inside the selected gutter opening.

Separate from hydraulic capacity

This indicative check assesses gutter position and overshoot risk. It does not change the gutter or outlet flow capacities.

mm
Measure down from the point where water leaves the roof to the top of the gutter.
mm
Horizontal distance from the gutter's back edge to the water release point.

The calculator will derive roof slope length from the horizontal roof width and pitch already entered above. Valley and upper-roof discharges will be flagged for a specialist check.