Page 32 - Build 161

Metal cap ashings should overlap wall claddings by: • 50 mm in L, M and H wind zones
• 70 mm in VH wind zones
• 90 mm in EH wind zones.
This measurement excludes the bird’s beak.
Parallel to roof slope
Apron ashings that are installed parallel to the roof slope must:
● for pro led metal roo ng (see Figure 2),
extend over at least two crests – E2/AS1
Table 7 and Figures 47 and 48
● extend over clay and concrete tiles for 150 mm
minimum and have the lead ashing dressed
into the pans – E2/AS1 Figure 26(a)
● for metal tiles, have a 40 mm minimum
upstand and a minimum over ashing cover of
35 mm – E2/AS1 Figure 35(a).
Hems and hooks
A hem or hook is required to ashing upstands in L, M, H and VH wind zones in addition to the dimension set out in E2/AS1.
Alternatively, the upstand dimension may be increased by 25 mm.
In EH wind zones, ashing upstands must have both a hem or hook and a 25 mm increase to the upstand dimension.
Cap ashings
Under E2/AS1, cap ashings must be installed over parapets or enclosed balustrades. They may be either metal cap ashings or butyl or EPDM membrane under ashings.
Metal capping ashings are detailed in E2/AS1: Figures 9 and 10 (see Figure 3). They must have:
● a minimum cross-fall across the top of 5°
● drip edges to both sides – use a bird’s beak drip
edge on the deck side of a balustrade
● expansion joints at maximum spacings of:
• 12 m for light-coloured steel and stainless steel
• 8 m for dark-coloured steel, copper and aluminium.
metal cap ashing xed through sides only
bird’s beak edge (for drip edge) where used as a balustrade
continuous horizontal batten cladding
minimum 5° slope
underlay to provide separation for metal cap ashing and timber packer
H3 9 mm 3 ply packed to give slope
packer
top plate
wall underlay continuous over top and both faces of balustrade
shaped polystyrene packer
top plate
wall underlay continuous over top and both faces of balustrade
Figure 3
Metal cap ashing.
textured coating over top and sides of balustrade
minimum 10° slope
additional layer of liquid waterproof membrane over base coats and under texture coat
continuous horizontal batten
Figure 4
Membrane under ashing to parapet/balcony wall.
30 — August/September 2017 — Build 161