The NZ Metal Roof and Wall Cladding Code of Practice is a comprehensive design & installation guide, and a recognised related document for Acceptable Solution E2/AS1 of the NZ Building Code.
A boot flashing is a proprietary EPDM flashing designed to weatherproof cylindrical penetrations protruding from a roof or wall. The top is trimmed to form a tight weatherproof collar around the penetration, and the base is formed with a series of concentric rings to the underside and a malleable stiffener of aluminium which is dressed to conform to the shape of the roofing profile. It is generally top-fixed to the roof surface with screws or rivets, and sealant.
The Profiled Metal Roofing COP allows pipe penetration flashings to be fitted directly to the profile or on to an over flashing. Pitch limitations depend on the method used and the cladding profile.
Direct-fixed options are pitch sensitive. When laid directly on to the profile at too low a pitch, they will entrap water rather than allow it to discharge over the profile crests that they traverse. The practical limits of direct-fixed boot flashings that cross an entire pan are 8° for standard corrugated and 10° for low rib trapezoidal products. Where the base of a boot does not obstruct a pan it can be direct-fixed to the minimum pitch for that profile.
Direct fixed applications for high rib trapezoidal profiles and trough sections vary according to the profile, and the size and position of the penetration. For these applications, the manufacturer should be consulted or the flashing can be attached to an over flashing, or a top fixed soaker type can be used.
Where the penetration is wide such as a chimney flue casing, and the penetration is far from the apex, soaker flashings may be used where the profile ribs are cut back so water can divert into the adjacent pan.
Where overall width is not a constraint, directly fixed boot flashings should be installed with their edges diagonal to the fall of water. Where this is not practical, they may be laid square at pitches of 10° or more.
Where boot flashings traverse a lap, the lap must be fully sealed or other actions must be taken to avoid leaks through capillary action. Where possible the fixing of a boot flashing over a lap should be avoided
The vertical sections of a boot flashing must not constrict the free flow of water. Where more than 50% blockage of the pan occurs other penetrations must be considered, or catchment calculations of the capacity of the remaining pan area should be made. (See 5.3.6 Gutter Capacity Calculator)