Page 38 - Build 153

DETAILING VALLEY GUTTERS AT THE POINT WHERE THEY INTERSECT WITH THE FASCIA BOARD
DESIGN
Valley gutters
Detailing around the intersection of a valley gutter and a fascia board can be a little tricky. Here are a few pointers.
RIGHT
BY ALIDE ELKINK,
FREELANCE TECHNICAL WRITER, WELLINGTON
CROSS-SECTIONAL DETAILS for valley gutters are given in both Acceptable Solution E2/AS1 and the NZ Metal Roof and Wall Cladding Code of Practice. However, neither document shows what happens at the fascia board/valley gutter intersection.
Current practice
Roof cladding is generally installed over purlins or battens, the top faces of which are generally aligned with the top of the fascia board (see Figure 1). This means that the roof cladding can be carried over the top of the fascia board to overhang and discharge into the spouting xed to the fascia board.
The valley gutter, however, is at a lower level than the roofing and therefore also at a lower level than the top of the fascia board. The usual way of dealing with this situation is to cut down the fascia board where the valley gutter intersects with it (see Figure 2), but the eaves spouting must not be cut down as this will compromise its capacity.
Requirements for valley gutters
Valley gutter requirements are set out in E2/AS1:
● They may only be installed where the roof
pitch is greater than 8°.
● They must have a minimum depth at the
centre of 50 mm.
● They must be a minimum of 250 mm wide if receiving run-o from a spreader.
Maximum catchment area
Maximum catchment areas for valley gutters are given in Table 8 of E2/AS1 for minimum roof pitch and gutter widths.
Where the roof pitch is between 8–12.5°, the: ● catchment area must be no more than
25 m2
● gutter must be at least 250 mm wide.
Where the roof pitch is 12.5° or greater, the:
● gutter catchment area must be no more than
16 m2
● gutter may be a minimum of 160 mm wide.
corrugated metal roo ng over roo ng underlay
purlin rafter
50 mm maximum underside of roo ng to back of spouting
underlay with 20 mm maximum overhang to spouting
50 mm minimum roof overhang for 10–30° pitch (40 mm minimum for pitch over 30°)
spouting
fascia board
Figure 1
Section A – section through eaves.
36 — April/May 2016 — Build 153