Page 40 - Build 153

Minimum roof overhangs
The roof overhangs to valley gutters vary accord- ing to the type of roof cladding (see Table 1), but E2/AS1 requires a minimum clearance of 50 mm between the overhangs to be maintained.
Where a valley gutter is less than 250 mm wide, for pro led metal and masonry tile roo ng, E2/AS1 allows the roof overhangs to be reduced to 60 mm to give a 40 mm clearance between overhangs.
However, a valley gutter with a minimum clearance of 100 mm allows the gutter to be accessed more easily for cleaning (see Figure 3).
The NZ Metal Roof and Wall Cladding Code of Practice also recommends increasing the minimum depth of the valley gutter to 75 mm where the roof pitch is between 8–12°.
Downpipe for catchment over 50 m2
Where a valley gutter discharges into an eaves spouting that has a total catchment area greater than 50 m2, a downpipe must be installed within 2 m of the valley (see Figure 4).
Gutters and upstands
Valley gutters should be fully supported and xed at the upper end only to allow for thermal expan- sion and contraction.
Upstands should be on both sides of the valley gutter and extend full height to the underside of the roo ng (see Figure 2). The upstands should be terminated with a hook and must not be xed under the roo ng.
Spreaders
Spreaders may not discharge directly into valley gutters.
Where a valley gutter receives run-o from a spreader, the gutter must be at least 250 mm wide.
Table 1
ROOF OVERHANGS TO VALLEY GUTTERS IN E2/AS1
TYPE OF ROOF CLADDING
MINIMUM ROOF OVERHANG TO VALLEY GUTTER
Pro led metal roo ng
80 mm
Masonry tile roo ng
100 mm
Pressed metal roo ng
50 mm
corrugated metal roo ng
downpipe spouting
Figure 4
50 mm minimum (E2/AS1) but 100 mm recommended
valley gutter
C
AB
2.0 m maximum if catchment roof area greater than 50 m2
Plan of valley gutter.
38 — April/May 2016 — Build 153