Aluminium Window Sill Flashing: Water Management, Weep Paths and Wall Interfaces

A window is tested as a product and installed as a junction, and the sill is where that difference becomes visible. In a laboratory the frame sits in a rigid rig with a clean edge and a controlled seal. On a building the same frame sits on a substrate that may be brick, render, timber or fibre-cement, surrounded by trades who each believe someone else owns the line. The sill flashing is the component that reconciles those conditions, and it is almost always the smallest item in the window package.

This article explains what a sill flashing is for, how water is meant to leave a window assembly, why end dams matter more than their size suggests, how membranes and wall interfaces change the detail, and why sequencing and sealant discipline decide whether the detail performs. It deliberately avoids dimensions, falls, commercial figures and performance values, because those belong to the project, the exposure category and the tested system rather than to a general guide.

The Purpose of a Sill Flashing

A sill flashing is a continuous, water-shedding element installed beneath and behind the window frame at the base opening. Its job is not to stop water from reaching the junction. Its job is to receive whatever water arrives there, control where it goes, and discharge it to the exterior without allowing it to reach the structure, the lining or the floor build-up.

That distinction matters because sealed joints fail. Movement, UV exposure, thermal cycling, poor preparation and simple workmanship all degrade sealant over the life of a building. A detail that relies on a bead of sealant as its only defence will leak as soon as the bead does. A detail built around a flashing assumes water will arrive and provides it with a route out.

Collecting Water That Has Already Passed the Outer Seal

Water reaches the base of a window through several routes: past the external glazing gasket, through the frame’s own drainage chamber, behind the cladding above, and by capillary action across apparently tight laps. None of these routes can be eliminated entirely in an openable window, which is why the assembly is designed to be drained rather than sealed shut.

The sill flashing is the collection point for all of them. It sits below the frame, extends behind the wall cladding line, and turns up at its rear edge so that water cannot continue inward. The frame’s drainage outlets, the flashing’s own fall and the front edge all combine to move that collected water back outside.

Protecting the Substrate and the Junction

Behind the flashing is the material that suffers most from prolonged moisture: the timber sill trimmer, the steel lintel over an opening, the masonry base course, the floor framing, or the internal lining and skirting. These materials do not need to be wet to fail. Repeated dampness, trapped between two impermeable layers and unable to dry, is enough to cause decay, corrosion and staining.

The flashing therefore performs a separation function as well as a drainage one. It keeps the frame, which is dimensionally stable and impervious, from sitting directly against materials that behave differently when they get wet. It also gives the waterproofing membrane a defined termination point, so that the wall’s weather barrier and the window’s weather barrier can be joined in a deliberate way rather than left to meet by accident.

Why the Sill Is the Hardest Line in the Envelope

Heads and jambs have gravity on their side. Water runs down them and away. The sill has gravity working against the detail in the sense that it is the lowest point, the place where everything above accumulates, and the place where the interior finish, the exterior cladding, the frame and the floor all converge.

It is also the line with the most trades. The carpenter sets the opening, the bricklayer or renderer closes the outside, the window installer fixes the frame, the waterproofing contractor terminates the membrane, the plasterer finishes the reveal, and the painter or sealant applicator closes the joint. Each of those operations can destroy the previous one, and none of them is usually responsible for the finished line as a whole.

The consequence is predictable. Sill defects are rarely caused by a defective flashing profile. They are caused by a flashing that was correct in principle but interrupted, reversed, punctured, buried or bypassed during the work that followed.

The Anatomy of a Sill Detail

Although details vary between systems and wall types, a well-resolved sill shares a set of functional parts. Each has a job, and each can be compromised independently.

Fall and Set-Out

The substrate beneath the flashing must be set out so that the flashing can fall to the exterior. A sill that is level, or worse, falling inward, holds water on the tray until it finds a lap or a fastener. The fall is small in appearance and large in consequence, and it is fixed at the framing or masonry stage, long before the flashing is delivered.

Set-out also determines whether the flashing can project beyond the finished face of the wall. That projection is what allows water to drip clear of the cladding rather than track back along the underside. If the frame is set too far out, the flashing has nowhere to go; if it is set too far in, the reveal becomes deep and the flashing is buried.

The Rear Upstand

The rear upstand is the vertical turn at the back of the sill tray. It provides the lap with the wall’s weather barrier and stops water from travelling inward across the tray. It must be continuous, it must be high enough to sit above any likely standing water on the tray, and it must not be interrupted by fixings that penetrate it below the water line.

Where the upstand meets the wall membrane, the membrane should lap over the upstand rather than the reverse. That way, water running down the wall passes onto the outside face of the upstand and continues to the tray, instead of finding the top edge of a reversed lap and entering behind it.

The Front Edge and Drip

The front edge of the flashing terminates the water’s journey. A formed drip, a kick-out or a projection past the cladding face encourages water to detach and fall clear. Without one, surface tension will draw water back along the underside of the flashing and into the wall, particularly in light wind-driven rain.

The front edge must also not be sealed to the cladding below in a way that traps water. A continuous bead along the front of the sill is one of the most common causes of concealed dampness, because it turns a drainage path into a shallow bath.

End Dams: A Concept, Not an Accessory

An end dam is the termination at each end of a sill flashing that prevents water from running laterally off the tray and into the wall cavity, the reveal lining or the adjacent construction. It is usually described as a component, but it is better understood as a principle: every flashing that collects water must have a defined boundary at every edge, and that boundary must be watertight and continuous with the tray itself.

What an End Dam Prevents

Water on a sloped tray flows downhill, but it also spreads sideways whenever the tray is level across its width or when the volume arriving exceeds the capacity of the outlets. Without an end dam, that lateral spread reaches the first available gap, which is usually the junction between the frame and the reveal, or the open cavity of the wall.

This is why end dams matter more than their apparent size. A sill can be perfectly sloped and perfectly flashed along its length and still deliver water into a wall at its corners, where the flashing stops and the membrane begins.

How End Dams Are Formed

In a formed metal tray, the ends are folded up as part of the same piece, so that there is no joint at the most vulnerable point. Where the tray is cut on site, the end must be folded, welded or covered by a purpose-made stop end that is sealed and mechanically restrained, not simply folded up and left open at the corner.

In membrane systems, the end dam is created by turning the membrane up the reveal and bonding it to the face of the opening, with the corner formed as a continuous saddle rather than a butt joint. In masonry, the flashing may be turned into the perpend or into a rake joint, with the ends of the cavity tray closed so that water cannot escape sideways into the inner leaf.

Where End Dams Fail

End dams fail in three recognisable ways. They are omitted at returns and stepped openings where the flashing changes direction. They are formed with sealant alone, which adheres to the tray but not reliably to a damp or dusty substrate. Or they are defeated by a subsequent trade, typically a renderer or plasterer who fills the corner and creates a bridge across the upstand.

The check is simple and should be recorded: at every end of the flashing, is there a continuous physical turn-up, and is it still intact after the cladding and lining are complete?

Weep Paths: Getting Water Out Again

A drained assembly only works if the water that enters can leave. Weeps are the openings that allow it to do so, but the opening itself is the least important part of the arrangement.

A Weep Is a Path, Not a Hole

For a weep to function, there must be an unobstructed route from the point where water collects to the exterior air. That route includes the cavity behind the frame, the space above the flashing, the outlet itself and the clearance in front of it. If any part of that route is blocked, the hole is decorative.

Blockages are usually introduced during construction rather than by design: mortar droppings on the tray, render pushed into the cavity, sealant smeared across the outlet, paint films bridging the slot, or cladding fixed hard against the face. Insect screens and vermin guards are useful, but they must be removable or cleanable.

Pressure Equalisation and the Air Path

Drained and back-ventilated details rely on the cavity behind the cladding being connected to the outside air, so that pressure differences across the assembly are reduced and water is not driven inward. Weeps serve that function as well as drainage. Sealing every opening in the name of weathertightness removes the ventilation and can make penetration worse, not better.

This is the reason a sill detail should be described as a system of openings, laps and chambers rather than as a line of sealant. The frame manufacturer’s drainage strategy and the wall’s cavity strategy have to be compatible, and both have to discharge at the same level.

Weeps in the Frame and Weeps in the Wall

Aluminium window frames usually have their own drainage outlets, positioned by the system designer at the lowest points of each chamber. Those outlets discharge onto the sill flashing, which then discharges to the exterior. The two systems are in series, and the lower one must not be blocked by the upper one’s hardware, packing or sealant.

Wall weeps, by contrast, ventilate and drain the cladding cavity above the flashing. They need to remain open after rendering, and they need to sit above the flashing upstand rather than in front of it. A common error is to align frame outlets and wall weeps precisely, so that a single blockage disables both.

Membranes and the Waterproofing Continuum

The flashing is only one element in a continuous waterproofing layer that runs from the wall above, through the opening, and back out to the cladding below. Membranes provide the flexibility and the continuity that rigid flashings cannot.

Sheet and Liquid Membranes

Sheet membranes, including self-adhered flashing tapes and vapour-permeable wall underlays, are used where movement is expected, where the substrate is irregular, or where a factory-controlled thickness is important. Liquid-applied membranes are used where geometry is complex, where penetrations must be detailed, and where a seamless coating is preferred around corners.

Both rely on the same disciplines: a clean, sound, dry substrate; a compatible primer where required; correct lap direction; and protection from damage until the cladding is complete. Neither performs reliably over a dusty, frozen or wet surface, and neither compensates for a substrate that is already saturated.

Laps and Direction

Every lap in a waterproofing system must be shingled so that water flows over the joint rather than into it. That means the upper element overlaps the lower one, in the direction of flow, at every transition: wall membrane over flashing upstand, flashing over membrane below, and membrane over the framing at the jambs.

Lap direction is easy to draw and easy to get wrong on site, particularly at the corners of an opening where the membrane must change plane twice. Pre-formed corner pieces, or a sequence of careful folds, are more reliable than a single stretched piece.

Compatibility and Bond Breakers

Membranes must be compatible with the flashing material, the sealant and the frame’s powder coating. Some bituminous products stain or attack certain finishes, and some sealants will not adhere to silicone-contaminated surfaces. Where a movement joint crosses the waterproofing line, a bond breaker is needed so that the membrane can accommodate movement without tearing.

The membrane also needs a defined termination at its top edge, mechanically restrained and sealed, so that water running down the wall cannot get behind it. An unsecured top edge is a funnel.

Wall Interfaces

The same functional sill behaves differently in each wall type, because each wall manages water differently and moves differently. A detail copied from one construction to another without adjustment is a common source of failure.

Masonry

Masonry is not waterproof. Brick, block and mortar absorb and transmit water, and the cavity behind them is the primary defence. At a window opening, the sill flashing works as a cavity tray: it spans the cavity, turns up against the inner leaf, turns down over the outer leaf, and includes a drip beyond the face.

Ends must be closed so that water cannot discharge into the cavity at the jambs, and weep holes must be left above the flashing at intervals set by the design. Mortar droppings must be cleared from the tray before the window is installed, because a hardened bed of mortar will dam the tray permanently. Ties, wall vents and any penetration through the flashing need their own seals and their own falls.

Rendered Walls

Render is a reservoir. It absorbs water, holds it, and releases it slowly, and it cracks where movement occurs. A sill detail in a rendered wall must therefore assume that the render will be wet and that water will reach the flashing long after the rain has stopped.

The render must terminate above the flashing on a stop bead or drip bead, with a clear break so that water can leave the render and fall onto the flashing rather than tracking behind it. Rendering over the flashing upstand destroys the lap. A movement joint at the sill line, aligned with the frame, reduces cracking at the transition. Sealant between the render and the frame should be a secondary line only.

Timber Framing

Timber framing is moisture-sensitive and dimensionally active, so the sill detail in a timber wall is built around a drained cavity and a flexible flashing. The wall underlay runs down behind the flashing, the flashing is dressed over it and turned up at the ends, and the frame is fixed through the flashing with the fixings sealed.

The critical detail is the interior side. Air sealing at the internal face prevents warm, moist air from entering the frame zone and condensing there, while the exterior remains vapour-open so that any water that does enter can dry outward. A sill that is sealed on both faces traps moisture in the one place it can do most damage.

Fibre-Cement Sheet

Sheet cladding is installed as a drained and ventilated facade, with joints that are designed to shed water rather than exclude it. At a window sill, the flashing must sit behind the sheet, project past the sheet face, and terminate with a drip that keeps water clear of the sheet below.

Sheets must stop above the flashing to leave a clear drainage and ventilation gap, and that gap must not be filled with sealant. Sheet joints near the sill need backing and careful alignment so that water is directed onto the flashing rather than behind it. Cut edges should be protected as the manufacturer requires, and fixings near the sill should not penetrate the flashing below the water line.

Sequencing: The Order That Decides the Outcome

Most sill failures are sequencing failures. The detail is correct on the drawing and impossible in the order it was built.

The Correct Order

The opening is formed and the substrate is set out with the required fall. The wall underlay or membrane is installed and terminated at the opening. The sill flashing is installed, with ends formed and fixings sealed. The frame is set, packed, fixed and checked for level and plumb. The frame’s own drainage is verified. The cladding or render is completed with its specified clearances. The sealant is applied last, to prepared surfaces, in the specified joints only.

Each step depends on the one before it. Flashing installed after the frame cannot be lapped correctly behind it. Membrane installed after the flashing cannot overlap the upstand. Sealant applied before the render is complete will be buried or damaged.

Hold Points Worth Recording

Three inspections catch most problems. The first is the substrate: fall, set-out, condition and cleanliness. The second is the flashing and membrane: continuity, lap direction, end dams, fixings and protection. The third is immediately before lining or cladding closes the detail: weeps clear, cavity clean, frame drainage open.

Photographs at each hold point are the cheapest form of quality assurance available, and they are the only record that survives once the wall is closed.

Sealants: Where They Belong and Where They Do Not

Sealant is a secondary barrier. It manages movement, excludes driven water at a defined joint, and finishes the line. It does not replace a flashing, and it cannot be used to create one.

Joint Geometry and Movement

A sealant joint needs a defined width and depth, a backer rod to control depth and prevent three-sided adhesion, and enough bond-breaker surface to allow the sealant to stretch. Sealant forced into a narrow gap between rigid materials will fail in adhesion or cohesion, usually within a season of thermal cycling.

Where two different materials meet, they move differently. The joint must be sized for that movement, not for appearance, and it must be continuous around the opening rather than interrupted at corners.

The Sealant That Causes the Leak

The most damaging sealant at a sill is the one applied along the front edge, under the frame, or across the weep path. It looks like diligence. It converts a drained detail into a container, and the water it traps finds the path of least resistance into the wall.

Equally damaging is sealant applied over a wet, dusty or contaminated surface, or over an existing sealant of unknown type. Adhesion failures of this kind are rarely visible from outside; they present as damp patches at the internal skirting, sometimes metres from the window.

Drainage: Three Paths and One Exit

Water in a window assembly follows three paths. The primary path is the external face: rain runs down the cladding, across the frame and off the sill. The secondary path is behind the cladding: water that passes the outer skin enters the cavity, lands on the flashing and drains out through the weeps. The concealed path is inside the frame and behind the lining, where water should never travel and where it does the most damage.

A well-designed sill keeps water on the first two paths and gives it one exit. A poorly designed one allows the third path to become the default.

What Blocks the Exit

Blocked exits are usually cumulative. A little mortar on the tray, a sealant fillet at the front edge, a sheet fixed too tight, a weep painted over, and a render bead that closes the gap. Individually each looks minor; together they seal the assembly.

The remedy is inspection at the point of closure, not after the leak appears. Once the wall is finished, restoring drainage usually means removing cladding or lining, which is far more disruptive than clearing a tray before it is covered.

Testing and Verification

Testing confirms that the installed assembly behaves as designed, but it does not replace design. A test on a defective detail either fails or, worse, passes because the test conditions do not represent the exposure.

Laboratory Evidence

Window systems are tested as assemblies under AS 4284, which sets out the sequence for air infiltration, water penetration and structural performance, among other checks. That evidence belongs to the system and its installation requirements. It does not transfer automatically to a different wall type, a different sill detail or a site-modified frame.

Site Water Testing

Site testing applies water to the completed junction under controlled conditions while the interior is observed. It is valuable for verifying workmanship, particularly at corners, end dams and frame-to-wall junctions, and it is the only way to check what was actually built.

Its limits should be understood. A site test samples the assembly rather than proving it, it cannot reproduce every wind-driven condition, and a pass at one location says nothing about the next window. Testing before sealant is complete and again after completion gives more information than a single test at handover.

Diagnosis When a Leak Appears

Diagnosis starts with the water’s route, not with the sealant. Is the leak active only during wind-driven rain, or after rain has stopped? Does it appear at the skirting, the reveal or the frame head? Is the sill tray holding water? Are the weeps clear? Is the render bridging the flashing?

Moisture meters, thermal imaging and borescopes help locate concealed water, and a staged hose test can isolate a zone. The objective is to find the entry point, not to seal the visible symptom.

Renovation and Replacement

Replacement windows in existing walls are the hardest case, because the original flashing is usually absent, damaged or inaccessible, and the new frame must connect to whatever is there.

Opening the Wall

Replacement work should assume that the sill must be exposed. Removing the old frame without opening the cladding usually means the new flashing cannot be lapped behind the wall membrane, and the joint is reduced to a sealant line. Where the wall is rendered or tiled, the opening should be cut back far enough to allow a proper termination and a matching repair.

The substrate must be inspected once exposed. A decayed sill trimmer, a corroded lintel or a saturated base course will not be fixed by a new window, and the opportunity to repair it is available only once.

Retrofit Trays and Surface Detail

Where opening the wall is not possible, a surface-mounted sill tray with formed ends and a drip can be installed over the existing sill, provided it can be lapped into the reveal and sealed at its back edge. This is a compromise: it relies more heavily on sealant, it changes the reveal depth, and it must still drain to the exterior.

Any retrofit must preserve the internal air seal and must not trap moisture between the new tray and the old substrate. Ventilation of the space between them, or a fully bonded approach, is a design decision rather than a default.

Heritage and Rendered Facades

Older masonry facades are often soft, irregular and painted with vapour-closed coatings. A new sill detail should allow the wall to dry inward or outward as it did originally, and should not introduce an impermeable layer that drives moisture into the masonry. Matching the existing profile and finish is part of the work, and the flashing should be as discreet as the performance allows.

The Regulatory Framework: NCC, ABCB and the Standards

In Australia, weathertightness at a window opening is addressed through the National Construction Code, administered by the Australian Building Codes Board. The NCC states performance requirements for external moisture, and the ABCB Housing Provisions provide deemed-to-satisfy detail for housing work. Compliance is demonstrated against the performance requirement, whether by deemed-to-satisfy provisions or by an alternative solution supported by evidence.

AS 2047 and AS 4284

AS 2047 covers windows and external glazed doors in buildings, including the performance and installation expectations for the product. AS 4284 sets out the test methods used to demonstrate that performance in the laboratory. Together they define what a window system can do and how that claim is verified.

Neither standard designs the wall junction. The sill flashing, the membrane termination and the interface with masonry, render, timber or fibre-cement remain project-specific, and the installation instructions that accompany a tested system are part of the evidence chain.

AS 1288 and AS 4666

AS 1288 governs the selection and installation of glass in buildings, including the structural and safety considerations that determine what can be used in a given location. AS 4666 addresses insulating glass units. Both matter at the sill because the glazing rebate is a water path: a poorly seated unit, a damaged edge seal or an inadequately drained rebate delivers water to the sill that the sill was not designed to handle in volume.

New Zealand

New Zealand regulates through the Building Code, with Clause E2 External Moisture setting the performance requirement for walls and openings. E2/AS1 is the Acceptable Solution commonly used for timber-framed buildings, and it sets out the drained cavity approach that sill details must support.

NZS 3604 covers timber-framed buildings, NZS 4223 covers glazing, and SNZ TS 4211:2022 addresses window performance. The principle is the same as in Australia: the product is tested, the installation is designed, and the junction between them is where compliance is either achieved or lost.

Common Failures and How They Present

No end dams. Damp patches at the reveal or the adjacent lining after wind-driven rain, with the sill itself apparently sound.
Reversed laps. Water behind the membrane, often visible as staining at the frame edge or bubbling paint.
Blocked weeps. Standing water on the tray, algae or sediment at the outlet, and leaks that begin after the first heavy storm rather than the first shower.
Sealant across the drainage path. Persistent damp at the internal skirting, worse after cleaning or painting.
Render bridging the flashing. Cracking along the sill line and water tracking behind the render bead.
Penetrated upstand. Fixings through the rear upstand below the water line, producing a slow leak that appears only in prolonged rain.
Missing internal air seal. Condensation and mould at the frame base in cool weather, often mistaken for a leak.

Documentation and Specification Checklist

A sill detail is only as good as the information that reaches site. The following items should be shown or specified, and should be checked at the hold points.

The sill substrate, its fall and its set-out relative to the finished facade.
The flashing material, its continuity, its end treatment and its fixings.
The lap with the wall membrane, including direction and termination.
The position and protection of weeps, and the clearance in front of them.
The frame’s own drainage outlets and their relationship to the flashing.
The cladding or render clearance above the flashing.
The sealant joints, their geometry and the surfaces they bond to.
The inspection and test records required before the detail is closed.

Frequently Asked Questions

What is the difference between a sill flashing and a sill?

The sill is the horizontal member at the base of the window, whether part of the frame or part of the wall. The flashing is the water-shedding layer beneath and behind it that collects and discharges water. A sill can be present without any flashing, which is exactly the condition found in many leaking buildings.

Can a sill flashing be installed after the window frame?

Only in a compromised form. Installing the frame first prevents the flashing from being lapped behind the frame and behind the wall membrane, so the detail depends on sealant at the most vulnerable line. Where the frame is already in place, the usual approach is to remove it, or to accept a surface tray with a reduced level of protection.

Are end dams always required?

Every flashing that collects water needs a defined boundary at its ends, so the principle always applies. How it is achieved depends on the wall type: a folded end in a metal tray, a turned-up membrane saddle in a framed wall, or a closed cavity tray end in masonry. What is not acceptable is relying on sealant alone.

Why do the weeps keep blocking?

Because debris arrives from above and because trades close the openings they find. Mortar, render, sealant, paint and tight cladding all reduce the path. The practical response is to protect the openings during construction, inspect them before the wall is closed, and keep them accessible for maintenance.

Should the joint at the front of the sill be sealed?

Generally not as a continuous bead. Sealing the front edge traps water on the tray and defeats the drainage. Where a joint must be sealed for appearance or air sealing, it should be designed so that it does not block the outlet path, and the decision should be shown on the detail rather than made on site.

Does a laboratory test guarantee the installed window will not leak?

No. Laboratory testing under AS 4284 demonstrates the performance of the system in controlled conditions. The installed performance depends on the wall interface, the flashing, the membrane, the workmanship and the sequencing, which is why site verification and inspection records matter.

How is a leaking sill best repaired?

By finding the entry point rather than sealing the symptom. That usually means exposing the sill, checking the end dams, the laps, the weeps and the frame drainage, and reinstating the detail in the correct order. Sealing the internal lining or painting over the stain leaves the water path intact.

What is different in New Zealand?

The regulatory documents differ, but the physics do not. Clause E2 of the Building Code sets the external moisture performance requirement, E2/AS1 provides the Acceptable Solution for timber-framed construction, and NZS 3604, NZS 4223 and SNZ TS 4211:2022 sit alongside it. The drained cavity and the flashing principle remain the same.

Conclusion

A sill flashing is a small element with a large responsibility. It receives the water that the window and the wall could not exclude, and it decides whether that water leaves the building or enters it. Its performance depends less on the profile than on the continuity of the waterproofing line, the integrity of the end dams, the openness of the weep paths and the order in which the trades worked.

Good practice is not complicated. Set the substrate out with a fall. Install a continuous flashing with formed ends. Lap the membrane over the upstand. Keep the cavity and the weeps clear. Fix the frame without penetrating the water line. Terminate the cladding and render above the flashing. Seal only the joints that should be sealed, and do it last. Inspect at the hold points and keep the records. Those steps apply equally to a masonry apartment building, a rendered house, a timber-framed addition and a fibre-cement facade, and they are what separates a sill that quietly works from one that is opened up within a year.

References

Australian Building Codes Board. National Construction Code 2025, Volume One and Volume Two, including the ABCB Housing Provisions. https://ncc.abcb.gov.au
Standards Australia. AS 2047, Windows and external glazed doors in buildings. https://www.standards.org.au
Standards Australia. AS 4284, Testing of building facades. https://www.standards.org.au
Standards Australia. AS 1288, Glass in buildings – Selection and installation. https://www.standards.org.au
Standards Australia. AS 4666, Insulating glass units. https://www.standards.org.au
Standards Australia. AS 2208, Safety glazing materials in buildings. https://www.standards.org.au
Standards New Zealand. NZS 3604, Timber-framed buildings. https://www.standards.govt.nz
Standards New Zealand. NZS 4223, Glazing in buildings. https://www.standards.govt.nz
Standards New Zealand. SNZ TS 4211:2022, Windows and doors performance. https://www.standards.govt.nz
Ministry of Business, Innovation and Employment. New Zealand Building Code, Clause E2 External moisture, and E2/AS1. https://www.building.govt.nz

Aluminium Window Sill Flashing: Water Management, Weep Paths and Wall Interfaces