Timber facings on aluminium joinery

E2/AS1 doesn’t have any details when you want to use timber head and jamb facings on aluminium window joinery. Here are a few pointers on what to think about.

Topics include

Windows & doors
By
Trevor Pringle
Last updated 19 May 2026
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E2/AS1 has a range of details for aluminium window sections used with direct-fixed and cavity claddings covered by the Acceptable Solution.

However, E2/AS1 does not have details where the aluminium section is used in conjunction with a timber facing.

Things to consider

When using a timber facing, there are several questions to be resolved:

  • What is the impact of adding the facing? For aluminium window flanges fitted over the facing, the window frame will be located further outside the line of the wall faming. Can the sill support bar be effectively installed to provide sufficient support?
  • Where does the facing sit in relation to the window flange – behind or rebated over?
  • What is the head detail going to incorporate – facing or weatherhead?
  • Where is the head flashing best located? In essence, there are two main options:
    • Directly above the aluminium flange with the facing over (see Figures 1 and 2, or Figure 3 for an alternative head detail).
    • Flashing the top of the facing – the traditional way timber windows were detailed (see Figures 4 and 5).

Note Sill options for this detail will be covered in the next Build.

Section diagram showing a window head detail with wall cladding, cavity space, window frame, and a horizontal flashing positioned above the window opening.
Figure 1 Head detail.
Section diagram showing a window set into a wall, with cladding, a cavity space, window frame, and a horizontal flashing extended above the window
Figure 2 Jamb detail.
Section diagram showing a window installed in a wall, with cladding on the exterior, a cavity space, the window frame, and layered wall framing around the opening
Figure 3 Alternative head detail.
Section diagram showing a window head detail with a sloping weatherhead above, a horizontal flashing over the window, and wall framing and layers around the opening
Figure 4 Head detail for flashing the top of the facing.
Section diagram showing a window installed in a wall, with cladding on the exterior, a cavity space behind the cladding, cavity battens, and a flashing detail above the window
Figure 5 Alternative jamb detail for flashing the top of the facing.