Spans

Stramit^® Gutters require the correct proprietary Stramit^® brackets (or snap clip/stiffener bracket combination) for support at spacing no greater than those shown in the following table.

STRAMIT® GUTTERS – MAXIMUM SUPPORT SPACINGS (mm)
Stramit® Quad 125 Gutter		1000
Stramit® Quad 150 Gutter		1000
Stramit® Quad 175 Gutter		900
Stramit Compact Gutter®		1200
Stramit® M Pattern Gutter		1200
Stramit Queenslander Quad® Gutter		1200

Gutter Capacity

In theory any size of gutter can be used to drain any roof catchment. What controls design is the number of downpipes needed to perform within the capacity of each gutter. In practice the larger the gutter the less the number of downpipes required, as indicated in the table [below].

Normally catchment calculations must take into account the increased area due to roof slope. The required downpipe table incorporated into this manual takes account of roof slopes up to 23°. Therefore the roof area for use with this table requires only the simple calculation of plan area.

Thermal Expansion

Gutter runs in excess of 20m require the provision of an expansion joint.

Fall

Stramit recommends that an absolute minimum fall of 1 in 500 be used for all gutters, this being a design requirement for the gutter and downpipe selection table. Good fall reduces the risk of leaf and debris deposition that could otherwise effect durability.

The selection of the number of downpipes is carried out in accordance with AS3500.3.2 (Stormwater drainage – acceptable solutions.) However, the larger the gutter the larger the downpipe required.The minimum size of downpipe associated with each Stramit® Gutter is given in the Stramit®Downpipes section that follows.