Aluminium Curtain Wall Glass Replacement: Site Safety, Gaskets and Drainage Continuity

Replacing glass in an aluminium curtain wall is not simply a matter of taking out a broken pane and ordering another pane of the same apparent size. A curtain wall is a coordinated system of mullions, transoms, pressure plates, caps, setting blocks, gaskets, sealants, spandrel zones, flashings and drainage paths. The replacement must fit that system and the building’s approved design intent. It must also be carried out without exposing workers, occupants, passers-by or adjacent finishes to avoidable risk.

This guide is a practical planning framework for Australian and New Zealand projects. It discusses access, exclusion zones, glass identification, removal and handling, gaskets, pressure plates, setting, edge protection, sealants, spandrels, drainage, weatherproofing, compatibility, quality assurance and handover. It does not replace the current National Construction Code (NCC), Australian Building Codes Board (ABCB) guidance, the applicable state or territory requirements, a project specification, a competent glazing contractor’s method statement, or advice from the system designer and a qualified building professional. Confirm the current edition and project application of every referenced document before work starts.

Start with a system investigation

Before anyone dismantles a panel, establish what curtain wall system is present and why the glass is being replaced. Look for project drawings, elevation schedules, glass schedules, maintenance records, previous repair reports, original supplier information and photographs taken before damage. Record the bay, level, elevation, grid reference and orientation. Note whether the defect is a crack, impact breakage, failed insulating glass, delamination, seal failure, water entry, condensation, optical distortion or a suspected frame movement problem. A pane that has failed because of an underlying movement or drainage issue may need more than a like-for-like substitution.

Inspect the visible frame and adjacent bays without disturbing components. Record mullion and transom condition, pressure plate joints, cap condition, gasket continuity, fasteners, sealant interfaces, corner details, spandrel panels, internal finishes and any signs of staining or trapped water. Photograph marks, labels, glass stamps and damaged parts. If the incident involved impact, preserve enough evidence to identify the cause and check whether neighbouring panes or anchors were affected. The investigation should distinguish between replacing a pane within an intact system and repairing a system that is no longer operating as designed.

Define the work boundary

Write the work boundary in plain language. Identify the exact panes, frames, adjacent materials and access equipment included. State what is excluded, such as structural investigation, repainting, replacement of unrelated gaskets, internal plaster repairs or remediation of concealed corrosion. If the boundary changes after opening the frame, stop and obtain a documented instruction rather than improvising. A narrow boundary protects the project from unrecorded assumptions and gives the final handover documents a clear scope.

Access, exclusion zones and worker safety

Access planning should precede glass procurement. The method may involve internal access, a mobile platform, a scaffold, a suspended access system, a boom lift or another controlled arrangement. The selected method must suit the elevation, wind conditions, reach, load, emergency arrangements and protection of occupants and the public. Equipment should be inspected, operated by appropriately trained people and used in accordance with its instructions and the site’s safety plan. Do not assume that an access method used for inspection is suitable for handling a large or heavy pane.

Establish an exclusion zone below and around the work face. Include the possible fall path of glass fragments, tools, pressure plates, caps, suction lifters and packaging. Control doors, paths, loading areas and occupied rooms that could be affected. Use physical barriers, signs and a spotter where necessary, and coordinate with building management so occupants are not directed through the work area. If glass is removed from an upper level, plan for windborne fragments and prevent materials from being placed where they can slide, tip or fall. The zone should remain controlled until the opening is secured and all loose components have been accounted for.

Prepare a rescue and emergency plan before work begins. It should cover a cut injury, a dropped object, access-equipment failure, sudden weather change, a pane that becomes unstable, and discovery of damaged structure. Confirm communication arrangements, first-aid resources and the location of safe storage for removed glass. Work should stop when conditions exceed the limits identified in the risk assessment, when visibility is inadequate, or when the team cannot maintain control of the pane and the surrounding area.

Protect people and the building

Protect internal floors, joinery, blinds, furniture, air-conditioning grilles and occupied spaces from dust, fragments and sealant residue. Use temporary screens only when they do not conceal a hazard or obstruct escape routes. Keep the opening weather-resistant between shifts. Do not leave a partially dismantled bay exposed to rain or wind without a planned temporary closure. Protect finished aluminium from scratches and avoid placing tools directly on visible caps or sills. Separate removed glass from reusable components and mark damaged parts so they cannot accidentally return to service.

Identify the replacement glass correctly

Visual appearance alone is not enough to identify replacement glass. Confirm the pane’s make-up, orientation, thickness, dimensions, edge condition, safety-glazing status, coating position, tint, colour, spacer, cavity arrangement, laminated interlayer where applicable, obscuration, manifestation and any required markings. Check whether it is monolithic, laminated, toughened, heat-strengthened, insulating glass or a combination. Identify whether the glass forms part of a vision panel, a spandrel panel, a fire or smoke-related assembly, an acoustic build-up, a balustrade-related condition or another specially designed zone.

Use permanent markings, glass stamps, records and controlled measurement. A stamp can help, but it does not by itself establish that a pane is suitable for the project. Measurements should account for the actual rebate, clearances, setting arrangement and gasket compression required by the curtain wall system. Confirm the measurement method with the system supplier or an experienced glazier. Do not infer a safe thickness, load capacity or performance classification from the size of a pane or from the fact that a similar pane was previously installed.

Apply the applicable glass safety requirements. In Australia, AS 1288 provides a central reference for the selection and installation of glass in buildings, while AS 2208 concerns safety glazing materials in building applications. The NCC and relevant ABCB provisions may also affect safety glazing, human impact locations, barriers, fire-related construction and other building conditions. In New Zealand, consult the current New Zealand Building Code, accepted solutions and verification methods, and relevant NZS 4223 guidance for glazing in buildings. The project designer or building consent authority may require additional documentation. Use the current standards, not an undated supplier summary.

Remove and handle the damaged pane

Before releasing restraints, assess whether the pane is stable. Cracked laminated glass may retain fragments but can still move unexpectedly. Damaged insulating glass may have sharp exposed edges. Toughened glass can fail suddenly if disturbed. Set up a controlled sequence for removing caps, pressure plates, gaskets and setting blocks. Mark components as they come off, record their orientation and keep fasteners with the relevant bay. Do not lever against a fragile glass edge, force a pressure plate that is still restrained, or cut a gasket without first confirming whether it is intended for reuse.

Use suitable glass-handling equipment for the pane and the access conditions. Check suction lifters, lifting frames, straps and protective pads before use. Clean contact surfaces so the lifting equipment can grip, but do not use cleaning products that leave a film. Keep hands clear of pinch points and maintain a clear instruction between the people controlling the pane. Carry and lower glass in the orientation specified by the handling plan. Store removed panes upright on stable, padded supports where they cannot slide, tip or contact hard edges. Broken glass should be contained and disposed of under the site’s waste and safety procedures.

After removal, inspect the rebate and frame. Look for displaced setting blocks, crushed gaskets, corrosion, distortion, blocked weep paths, failed joints, loose fasteners, debris and damage to coatings. Check whether the pressure plate is straight and whether its screw holes or fixing points remain sound. Record concealed conditions with photographs. Clean only as far as the approved method allows; aggressive scraping or solvents can damage coatings, thermal breaks, finishes and compatible sealant surfaces.

Gaskets, pressure plates and edge protection

Gaskets are functional components, not decorative strips. Confirm whether the system uses internal and external wedge gaskets, co-extruded seals, vulcanised corners, spliced lengths or a specified profile with a particular hardness and material. A gasket that looks similar can have the wrong bite, height, compression or compatibility. Reuse should be permitted only when the gasket is undamaged, resilient, clean, correctly identified and allowed by the system information. Brittle, stretched, cut, permanently compressed or contaminated gaskets should not be treated as serviceable.

Install gaskets in the correct direction and sequence. Avoid stretching a gasket into the opening because it may shrink back and create a gap. Form corners in accordance with the system detail rather than forcing a square bend into a profile that requires a prepared joint. Keep drainage slots and pressure-equalisation routes clear. Gasket ends should meet using the specified joint arrangement, and any corner treatment should match the system supplier’s detail. Do not apply unapproved adhesive, lubricant or sealant to make a poor fit appear secure.

Pressure plates transfer restraint through the intended line of the system. Inspect the plate for distortion, corrosion, damaged threads and missing fasteners. Refit it in the correct orientation and use the specified fixing sequence and tightening approach. Over-tightening can crush gaskets, distort the frame or damage glass edges; under-tightening can leave inadequate restraint or allow movement. If a project requires a defined torque, joint treatment or fastener replacement, follow the documented requirement and record the result. Do not invent a torque value or substitute a fastener solely because it appears to fit.

Glass edges need protection throughout installation. Maintain the designed edge clearance and prevent direct contact with aluminium, steel, screws, pressure plates or hard debris. Use approved setting blocks of the correct material and configuration. Keep blocks in their intended positions and do not use random packers to correct a measurement error. If an edge has been chipped, scratched or otherwise damaged, seek a disposition from the responsible technical party before installation. Concealing edge damage under a gasket does not restore the glass’s condition.

Setting, alignment and spandrel zones

Setting supports carry the pane in the way intended by the curtain wall design and help maintain edge clearances. Confirm the support locations, block material, bearing arrangement and compatibility with the glass and sealants. Set the pane without forcing it into a distorted opening. Check sightlines, joints, level, plumb and relationship to adjacent panes before final restraint. A visually aligned pane can still be incorrectly supported, so the installer should record the setting method and any approved adjustment.

Spandrel areas require particular care because they can conceal opaque glass, insulation, back pans, fire-stopping, slab-edge interfaces and other non-vision elements. Do not replace a spandrel pane with vision glass or change an opaque build-up without confirming the design consequences. Maintain the intended cavity, insulation, ventilation, fire and weather details. If the replacement exposes a slab edge, back pan, bracket or fire-stopping element, stop and obtain direction. The opening should not be used to relocate services or alter a fire or smoke compartment.

Sealants and weatherproofing continuity

Sealant is part of a joint design, not a universal repair paste. Identify each joint’s function: weather seal, air seal, bedding, end dam, corner treatment or another interface. Confirm the sealant type, primer requirement, substrate preparation, movement capability, cure conditions and compatibility with glass coatings, gaskets, powder coatings, anodised finishes, membranes and adjacent sealants. Follow the manufacturer’s current technical data and the project specification. Do not mix sealant brands or chemistries in a joint without documented compatibility.

Remove failed sealant to the extent required by the repair detail without damaging the substrate. Clean and dry the joint using approved materials. Keep backer materials and bond-breakers in their intended position, and avoid three-sided adhesion where the joint design requires two-sided movement. Tool the sealant to provide continuous contact and a neat, serviceable finish. Sealant should not bridge drainage openings, block pressure-equalisation paths, cover weep slots or trap water behind a pressure plate. Respect the cure time before exposing the joint to movement or water.

Weatherproofing continuity is best considered as a path. Trace the outer seal, pressure-equalised cavity, inner air seal, sill drainage, end dams, transom intersections, mullion joints and interfaces with adjacent construction. A new pane can be correctly glazed yet still leak if a nearby joint is open or a drainage path is blocked. Where water testing is proposed, define the method, location, equipment, duration, acceptance criteria and authority before testing. A local test is evidence about the tested area under the stated conditions; it is not automatically proof of whole-facade performance.

Drainage continuity and condensation awareness

Curtain wall cavities commonly rely on controlled drainage and pressure equalisation. Keep weep holes, slots, channels, end dams and outlet paths open. Remove glass fragments, gasket offcuts, sealant tails, dust and packaging before closing the pressure plate and cap. Check that a replacement gasket has not folded across a drainage route. Ensure the sill and transom interfaces are assembled as shown in the system details. Do not drill new holes or create an improvised outlet without approval, because an unplanned opening can compromise pressure management, corrosion protection or adjacent materials.

Drainage checks should include the areas above and below the replacement, not only the pane itself. Look for staining, wet insulation, salts, mould, corrosion and evidence of repeated water entry. Condensation may arise from indoor humidity, thermal bridges, air leakage or a changed glass configuration, and it should not automatically be labelled a leak. Record observations and refer complex condensation or moisture problems to the appropriate building-envelope professional. The repair should preserve the intended separation between water-shedding surfaces, drainage cavities and internal air seals.

Replacement compatibility and evidence boundaries

A replacement is compatible only when the complete assembly remains suitable for its intended location. Compatibility includes glass type, dimensions, weight, edge clearances, support, coatings, gaskets, pressure plates, sealants, drainage, movement, thermal behaviour and relationship to adjacent construction. It can also include fire, smoke, impact, acoustic, energy and safety requirements where those requirements apply. A supplier’s statement about a glass product does not automatically certify the installed curtain wall configuration.

AS 2047 may be relevant to windows and external glazed doors, while AS 4284 is a key reference for the testing of building facades and curtain wall assemblies. These standards should be applied according to their scope and the project’s design and testing brief. AS 4666 may be relevant where the project addresses the maintenance or assessment of insulation and related building-envelope performance. None of these references should be treated as permission to claim a rating that has not been documented for the actual assembly.

For New Zealand work, coordinate the replacement with the New Zealand Building Code, the current acceptable solutions or verification methods, NZS 4223 guidance for glazing and any project-specific façade or window requirements. NZS 4211 and other relevant New Zealand documents may apply depending on the product and project scope. The exact applicability should be confirmed by the designer, supplier and consent authority. Australian and New Zealand guidance is not interchangeable by assumption, even where the physical curtain wall appears similar.

Keep evidence boundaries explicit. Manufacturer literature can describe a product or system; a project calculation can address a particular building; a laboratory test can cover a stated specimen and procedure; an on-site inspection can record visible workmanship; and a water test can cover the area and conditions actually tested. Do not combine these evidence types into a broader certification claim without the responsible professional’s basis. Do not invent wind pressures, water pressures, thermal values, acoustic values, fire ratings, certifications, guarantees, prices or dimensions.

Quality assurance and inspection records

Use a hold-point plan. A pre-start hold point confirms the approved work method, access, exclusion zone, replacement identification and weather conditions. A removal hold point confirms that the pane is safe to release and that concealed conditions have been recorded. A frame-preparation hold point confirms cleanliness, gasket condition, drainage and pressure-plate suitability. A glazing hold point confirms glass orientation, edge protection, setting blocks, alignment and restraint. A sealant hold point confirms preparation, joint continuity and cure requirements. A final hold point confirms caps, gaskets, drainage, cleaning and records.

Record the pane location, date, personnel, glass identification, supplier documents, batch or traceability information where available, component replacements, sealant details, photographs and any deviations. Record who inspected each hold point and what was accepted, rejected or referred. If a deviation is accepted, retain the written disposition rather than relying on a verbal instruction. The record should identify unresolved items and the person responsible for closing them.

Inspect from appropriate internal and external viewpoints. Check for glass damage, visual defects, coating orientation, gasket roll, pressure-plate continuity, cap engagement, open joints, sealant voids, contamination, uneven sightlines, blocked drainage and damage to adjacent finishes. Confirm that temporary protection has been removed without disturbing the repair. If testing is specified, retain the test method, equipment information, location, result and limitations. A failed test should trigger investigation of the path, not a cosmetic application of more sealant.

Handover and maintenance information

Handover should provide more than a statement that the pane was replaced. Include marked-up location information, photographs before and after work, the glass identification, relevant supplier documentation, installed component details, sealant product and cure information where required, inspection records, test records, approved variations and outstanding maintenance actions. State what was inspected and what was outside the repair scope.

Explain cleaning and maintenance requirements to the building owner or facilities team. Identify products or methods that could damage coatings, gaskets or sealants. Provide instructions for reporting new cracks, fogging, staining, loose caps, failed gaskets or recurring water entry. Maintenance personnel should know that weep paths and joints must not be sealed, painted or obstructed during later works. Keep the records with the building’s façade maintenance information so a future repair team can understand the assembly rather than repeat the original investigation.

Frequently asked questions

Can a broken curtain wall pane be replaced with glass that looks the same?

No. Appearance is only one identification factor. Confirm the glass construction, safety status, dimensions, edge conditions, coatings, cavity or interlayer, support requirements and project performance obligations. The correct replacement must be compatible with the complete curtain wall assembly and its documented design.

Should the old gasket always be reused?

No. Reuse depends on condition, identification, resilience, cleanliness and the system requirements. A stretched, brittle, cut, permanently compressed or contaminated gasket should be replaced with the specified compatible profile. Never use sealant or adhesive as an unapproved substitute for a correctly fitting gasket.

How can a repair team avoid blocking drainage?

Map the drainage and pressure-equalisation paths before dismantling. Keep weep holes, slots, channels, end dams and sill outlets clear of fragments, gasket offcuts and sealant. Inspect the path before closing the pressure plate and cap, and include drainage in the final quality checklist.

Does a local water test prove that the whole curtain wall is weatherproof?

No. A local test provides evidence about the tested area, method and conditions. It does not automatically establish the performance of every bay, joint or elevation. Define the test scope and acceptance criteria in advance, and investigate failures through the complete water-management path.

Is AS 2047 by itself enough for a curtain wall replacement?

Not necessarily. The applicable requirements depend on the project, system, location and scope. Curtain wall and façade testing may involve AS 4284, while glass safety and material requirements may involve AS 1288 and AS 2208. NCC and ABCB provisions, project specifications and professional advice also matter. Use each document within its proper scope.

What should be retained for handover?

Retain the pane location, glass identification, supplier information, photographs, component and sealant records, inspection approvals, test evidence, approved deviations and maintenance instructions. Also record limitations, exclusions and any unresolved issue. This makes a later inspection safer and prevents unsupported performance claims.

Conclusion

Successful aluminium curtain wall glass replacement is a controlled building-envelope repair. It begins with identifying the system and defining the work boundary, then protecting people and the building through planned access and exclusion zones. It continues with verified glass identification, controlled removal, sound edge protection, correct setting, compatible gaskets, disciplined pressure-plate installation, carefully prepared sealants and uninterrupted drainage. Spandrel zones, adjacent joints and concealed conditions must be treated as part of the assembly, not ignored because the visible pane has been changed.

The strongest handover is evidence-led and modest in its claims. It records what was installed, inspected and tested, identifies what was outside scope, and keeps NCC, ABCB, AS 4284, AS 2047, AS 1288, AS 2208, AS 4666 and relevant New Zealand guidance in their proper context. With that discipline, a replacement can restore a damaged opening while preserving safety, weather management and future maintainability.

Aluminium Curtain Wall Glass Replacement: Site Safety, Gaskets and Drainage Continuity