Repair Systems — 03 — Facade & External Envelope
Sill Flashing
Technical product reference for sill flashings at facade cladding panel openings — stainless grade 316 and aluminium sill tray flashings, kickout sill flashings, and sloped-sill profiles at window and door sill junctions. Sill flashings must drain to the exterior and include an upturned back leg to prevent water tracking back to the wall substrate.
What are sill flashing systems?
Sill flashings form the waterproof tray at the base of all window and door openings in a rainscreen cladding system — collecting water that penetrates the outer cladding and directing it back to the face through weep holes. A correctly detailed sill flashing with upstand, end dams, slope, and anti-capillary nose is the single most important waterproofing detail in a cladding facade.
Product Reference
4 product systems — sill flashing — scroll to view all
SS316 Sloped Sill Flashing
Factory-Folded Sill Flashing — SS316
System Description
316L stainless sill flashings are factory-folded with a minimum 5° slope to the outer face, a 50 mm upstand at the back against the substrate, and an anti-capillary groove at the drip nose. The upstand is critical — it prevents water from tracking back into the wall at the critical sill-to-wall junction. The sill pan collects any water penetrating the cladding system and directs it to the outer face. End dams at each side are factory-welded. For marine zone applications (< 200 m from ocean) and all coastal high-rise facades where 50-year maintenance-free performance is required.
Technical Properties
- Material: 316L stainless — 1.5 mm
- Slope: 5° minimum to outer face (factory-formed)
- Upstand: 50 mm minimum at back leg
Limitations
- Factory lead time: 3–6 weeks — must be included in programme
- Shop drawings required before fabrication
- Upstand must remain clear of insulation — thermal bridge if blocked
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
Anodised Alum Sill Flashing
Anodised Aluminium Sill Flashing
System Description
Factory-folded 6063-T5 anodised aluminium sill flashings with sloped pan, 50 mm upstand, and end dams are the standard sill flashing for coastal zone cladding applications. Class 2 anodising (20 micron) provides long-term corrosion resistance in coastal zones (200 m–1 km from marine water). The sill pan slopes 5° to the outer face to direct water through the front weep holes. Lighter and less expensive than stainless, anodised aluminium sill flashings are appropriate for the majority of Australian cladding remediation projects outside the marine zone.
Technical Properties
- Material: 6063-T5 aluminium
- Gauge: 1.6 mm
- Anodising: Class 2 — 20 micron (Class 3 for marine-adjacent)
Limitations
- Not suitable for marine zone < 200 m — specify SS316
- Anodising scratches on site — protect during installation
- High thermal expansion: allow for movement at joints (25 mm per 10 m at 50°C delta)
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
Colorbond Sill Flashing
Colorbond Steel Sill Flashing
System Description
Colorbond Ultra sill flashings are colour-matched to the building facade palette — suitable for residential and light commercial applications where sill flashing will be visible. Factory-folded with a 5° slope, 50 mm upstand, and end dams. Colorbond Ultra base material is rated C4 (coastal) — suitable up to 1 km from marine water. Cut edges must be treated with zinc-rich primer. Commonly specified as the matching sill flashing in Colorbond-walled buildings or FC panel cladding with Colorbond trim.
Technical Properties
- Material: Colorbond Ultra — ZAM alloy
- Gauge: 0.55 mm BMT
- Slope: 5° minimum
Limitations
- Not suitable for marine zone < 1 km ocean — use SS316 or anodised alum
- Cut edges corrode — zinc-rich primer required within 24 hr
- Colour must match current Colorbond chart — confirm before ordering
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
Alum Sill Flashing + EPDM
Sill Flashing with Integrated EPDM Upstand Seal
System Description
Aluminium sill flashings with factory-bonded EPDM compression seal at the upstand-to-wall interface eliminate the need for sealant at this critical junction. The EPDM seal accommodates thermal movement between the aluminium flashing and the substrate (concrete, masonry, or FC panel) without cracking — the most common failure mode of sealant at sill flashings. The seal compresses when the flashing is mechanically fixed — no adhesive or additional sealant is required at the upstand. Reduces ongoing maintenance requirements and eliminates sealant failure as a water ingress pathway.
Technical Properties
- Material: 6063-T5 anodised aluminium
- EPDM seal: 3 mm bulb — 70 Shore A
- Factory-bonded EPDM to back of upstand leg
Limitations
- EPDM seal requires uniform compression against flat substrate — gaps > 2 mm will fail
- Field-damaged EPDM cannot be replaced — handle with care
- Sealant still required at end dam laps and lateral joints
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Comparison
Side-by-side comparison of sill flashing systems. Confirm all product selections against the current manufacturer TDS before specifying.
| Product system | Material | Zone | Upstand | Slope | EPDM seal | Primary use |
|---|---|---|---|---|---|---|
| SS316 Sloped Sill | 316L Stainless | Marine | 50 mm | 5° | No | Marine / high-rise 50 yr |
| Anodised Alum Sill | 6063-T5 Anodised | Coastal | 50 mm | 5° | No | Standard coastal cladding |
| Colorbond Sill | Colorbond Ultra | Coastal (C4) | 50 mm | 5° | No | Colour-matched residential |
| Alum + EPDM Seal | 6063-T5 Anodised | Coastal | 50 mm | 5° | Yes | No sealant at upstand joint |
Do not confuse sill flashings with:
- Window sill extension or internal sill — internal sill boards and lining materials provide a decorative finish inside the window reveal; sill flashings are external weatherproofing elements that discharge water away from the wall and must form a continuous upstand behind the window frame
- Drip edge only — a drip edge without an upstand does not function as a sill flashing; a compliant sill flashing must have a positive slope, an upstand turning up behind the frame, and a drip groove or edge to prevent water re-entry
- Backer rod and sealant used as a sill — sealant is a secondary sealing element; it is not a substitute for a properly shaped and installed sill flashing that mechanically drains water away from the window-to-wall junction
- Lead flashing used as a sill — lead sill flashings exist in heritage buildings but are prohibited for new or remedial work in most jurisdictions in Australia; replacement sill flashings must use aluminium, SS 316, or Colorbond depending on zone
Disclaimer
Information is general only. Sill flashing profiles, slope, upstand heights, and fixing methods must be confirmed by a facade engineer against the specific window and cladding system design. Sill flashing must be designed to drain water to the exterior — inadequate slope or upstands are a primary source of water ingress defects. Do not rely on this reference as a substitute for professional engineering advice.