Cladding & Wall Systems

Cladding is any external wall system hung on or fixed to a structure rather than built up from the ground as masonry: precast concrete panels, metal composite and solid aluminium panels, stone veneer on brackets, terracotta and ceramic rainscreen, fibre cement and render systems on framing, exterior insulation and finish systems (EIFS), insulated sandwich panels, and timber or fibre cement weatherboards. Masonry has its own page. The system is more than the face: it includes the support framing or brackets, fixings, any insulation, the sheathing or sarking behind, cavity barriers, and the joints and flashings that make it weathertight.

Every system manages rain in one of three ways, and the way it manages rain decides how it fails. Face-sealed (barrier) systems stop water at the outer surface and rely entirely on sealant joints; when a joint fails, water is inside with no way out. Most precast of the 1960s to 1990s, early EIFS and much render on sheet are face-sealed. Drained and ventilated (rainscreen) systems accept that water passes the face, and drain it down a cavity to flashings and weep points, with a sealed line behind. Most modern panel, terracotta and weatherboard systems work this way. Mass systems absorb and release water, as solid masonry and thick render on masonry do.

Building class shapes the risk. Apartments carry the combustibility and water-trapping legacy of the 1995 to 2018 period and are the focus of the cladding regimes in all three jurisdictions. Offices carry precast and stone with ageing fixings. Industrial buildings carry sandwich panels whose core type matters more than their appearance. Houses carry weatherboards and render, where the paint and the ground line decide the life.

What shortens life:

• Face-sealed detailing on any system with framing behind it: one failed joint wets the frame with no route out.
• Missing or reversed flashings at window heads, sills, floor lines and parapets; water directed into the wall rather than out of it.
• Coastal and industrial exposure, which consumes coatings and corrodes carbon steel fixings and cut edges.
• Dissimilar metals: aluminium rails on galvanised brackets, stainless fixings in aluminium without isolation, copper runoff.
• Impact at ground level and on balconies, which opens EIFS and render and exposes sandwich panel cores.
• Deferred sealant renewal on face-sealed systems.
• Ground and paving too close to the bottom of weatherboards, render and sheet.

Water trapped behind the face

Face-sealed EIFS, render on sheet and fibre cement without a cavity are only as good as their joints and their window details. When a sill or joint fails, water reaches the sheathing and frame and stays there. Timber frames rot; light steel frames corrode at the bottom track; oriented strand board and plywood sheathing delaminate. The face can look sound for years while the frame behind fails, which is how the leaky building crisis in New Zealand and the EIFS litigation in the United States unfolded.

Fixing corrosion

Precast panels hang on cast-in ferrules, bearing angles and restraint fixings; stone hangs on dowels, cramps and kerf clips; panel systems hang on brackets and rails. Carbon steel fixings corrode where water reaches them. Expanding corrosion cracks the stone or concrete at the anchor and can release a section of panel. Section loss in hidden hangers is the most serious failure mode of heavy cladding because it gives little external warning.

Reinforcement corrosion in precast

Thin precast panels often have little concrete cover over the reinforcement, especially at edges, ribs and returns. Once carbonation reaches the steel, or chlorides from coastal air do, the steel corrodes and spalls the concrete face, usually in lines that follow the bars.

Stone bowing and delamination

Thin marble panels lose strength and bow permanently under repeated heating and cooling (thermal hysteresis), dishing outward or inward. Sandstone and some limestones delaminate when laid face-bedded. Bowed and delaminated stone cracks at its anchors.

Combustibility

Metal composite panels with a polyethylene core, EPS-cored sandwich panels, some high-pressure laminates and timber, foam insulation in cavities, and missing or misplaced cavity barriers can carry fire up and across a façade. This is a design and compliance issue, not a condition issue: an immaculate panel can be the most serious item on the building.

Panel and coating failure

Coated metal panels chalk and fade, then lose coating at edges and cut lines; composite panels can delaminate where skins debond from the core. Sandwich panels corrode from cut edges and fixings, and their cores degrade when wet. EIFS and render crack at sheet joints, around openings and from impact, and lose bond to the substrate.

Weatherboard decay

Timber weatherboards decay where paint fails at end grain, at the ground line, and behind downpipes and gutters; boards cup and split as they cycle wet and dry. Fibre cement boards crack at fixings and lose coating; edges absorb water where unsealed.

From the street and from aerial imagery

• Panel type and joint pattern: wide open joints suggest rainscreen; narrow sealed joints on every panel edge suggest face-sealed.
• Cracked, spalled or rust-stained precast, with staining in lines following reinforcement or at panel corners where fixings sit.
• Bowed stone panels visible in raking light; cracked stone at corners and anchor positions; missing or replaced panels in a different shade.
• Staining below window corners and sills on render and EIFS; cracks running from window corners; patched areas.
• Faded, chalked or peeling panel coatings; rust at sandwich panel laps and cut edges; dented panels at ground level.
• Weatherboards with peeling paint, split boards, decay at ends and at ground line; boards close to or below paving.
• Netting, hoarding or temporary covers on a façade, which mean someone has already found something.

Close up on site

• Soft or bulging render and EIFS when pressed; hollow sound when tapped; cracks at sheet joints.
• Moisture readings and soft spots in framing behind sheet systems, taken at sills, the bottom plate and below windows.
• Movement of stone or precast panels when pushed; cracking at anchor positions; rust bleeding from joints.
• Panel labels or markings on the back of composite panels where a panel can be removed; the core visible at cut edges.
• Cavity barriers present or absent at floor lines and around openings, where a panel can be lifted.

Inside the building

• Damp, mould and swelling at window reveals, at skirtings on external walls and at the base of walls under sills.
• Stained ceilings below parapets and at slab edges; corrosion at exposed light steel framing in plant rooms or ceilings.
• Musty smell in apartments with framed external walls, a common early sign of hidden decay.

In the records

• Cladding audit, fire engineer report, regulator correspondence or registration on a state or national cladding programme.
• Insurance exclusions or loadings referring to the external walls or panel cores.
• Defect claims, expert reports and rectification orders on apartment buildings.
• Repeated leak repairs at the same windows or elevations; sealant renewal history.

Findings are graded by what they demand: safety (can hurt someone now), failure (failed and damaging the building), condition (distress present and progressing), lifecycle (renewal due on age and exposure), deadline (a regulator or ordinance sets the date), check (investigate before sizing works) and nil (cosmetic or stable).

A façade engineer leads on panel and stone systems; a building surveyor can lead on houses and low-rise weatherboard and render. Combustibility is assessed by a fire engineer, and in Britain by an assessment under PAS 9980 for residential buildings in scope.

• Desk review of drawings, product certificates and any audit, to identify the system and its fixings before going on site.
• Close-up survey from rope access or a platform, every elevation over public areas, a representative sample elsewhere.
• Opening up at representative locations: sills and heads of windows, floor lines, parapets and the base of walls on framed systems; panel removal on rainscreen to see brackets, rails, insulation and cavity barriers; fixings exposed on precast and stone.
• Moisture probing of framing behind sheet and EIFS systems at the high-risk points, with probes left in place for monitoring where the wall will not be stripped.
• Concrete testing on precast: cover survey, carbonation depth, chloride content at the depth of the steel.
• Fixing testing: pull-out tests on stone anchors and remedial fixings; section loss measured on exposed hangers.
• Core identification of composite and sandwich panels by sample and laboratory test where records do not settle it.
• Water testing of windows and joints to locate leak paths before remedial design.

The report should state the system and how it manages water, what was found behind it, fixing condition, combustibility status, and remedial scope by elevation with measured extents.

• Local repair: reseal joints, repair precast concrete to a recognised repair standard, replace individual panels and boards, repair render and recoat.
• Fixing remediation: supplementary stainless anchors drilled through panels or stone into the structure; replacement of corroded hangers, which can require panels to be removed and rehung.
• Recladding: removal of the system and replacement with a drained and ventilated system, including new sheathing, membrane and flashings, and frame repair where decayed. This is the usual answer for failed face-sealed systems on framing and for combustible panels.
• Overcladding: a new rainscreen fixed over an existing sound wall, used on precast and masonry where the substrate is sound and the joints are not worth renewing.
• Combustible cladding: replacement with non-combustible panels and insulation, reinstatement of cavity barriers, and interim measures (fire watch, alarms, changed evacuation strategy) until complete.
• Weatherboards: replace decayed boards, seal ends, restore ground clearance, repaint on cycle.

Interactions: recladding carries window, sealant, flashing and balcony work with it; scaffolding or access dominates; on occupied apartment buildings the programme is often elevation by elevation; heritage listing can restrict materials.

Investigation is a lump sum with rates per opening, test and sample. Recladding and overcladding are measured by façade area, with separate lines for windows, flashings and frame repair found on opening up. Fixing remediation is priced per anchor or per panel. Panel replacement and board replacement are rate-based. Access is often the largest single component.

Combustible cladding rectification is a lump-sum project with consultant, approval and interim measure costs, coded as code compliance with its timing driven by the regulator. Recladding of a failed face-sealed system is lifecycle or repairs, with the frame repair a conditional line sized from opening up. The usual register shape is two-part: investigation first, then a conditional works envelope.

• Australia. The National Construction Code requires external walls of Type A and Type B construction to be non-combustible, tested to AS 1530.1, with performance solutions tested to AS 5113. State regimes act on combustible cladding: Cladding Safety Victoria administers rectification of high-risk buildings, New South Wales bans aluminium composite panels with more than 30 per cent polyethylene core on certain buildings under the Building Products (Safety) Act 2017 and runs Project Remediate, and Queensland ran a combustible cladding checklist programme. On strata buildings, cladding is common property; rectification and defect claims sit with the owners corporation.
• United Kingdom. Approved Document B and regulation 7(2) prohibit combustible materials in the external walls of relevant buildings 18 m and over; the Building Safety Act 2022 places duties on accountable persons for higher-risk buildings, creates remediation orders and protects many leaseholders from remediation costs. PAS 9980:2022 sets the method for fire risk appraisal of external walls. The Cladding Safety Scheme and Building Safety Fund fund remediation of eligible buildings; lenders rely on EWS1 forms.
• United States. International Building Code Chapter 14 governs exterior walls, with NFPA 285 testing required for combustible components on most buildings of Types I to IV construction; EIFS follows ASTM E2568. Façade ordinances in New York, Chicago, Boston, San Francisco and others require periodic critical examination of cladding on taller buildings; New York's Cycle 10 runs from February 2025 to February 2029.

• Façade drawings, specifications and product certificates naming each system, panel core and insulation.
• Any cladding audit, fire engineer report, PAS 9980 assessment, EWS1 form, regulator correspondence or order.
• Façade inspection reports and ordinance filings.
• Records of panel replacement, fixing remediation, recladding or overcladding.
• Leak logs, defect claims and expert reports on framed systems.
• Insurance terms referring to external walls.
• Repaint history for weatherboards and render.