Façade & External Envelope
Failed Sealants & Joints
Facade sealant and movement joint failure is among the most frequent causes of water ingress in Class 2 buildings. Sealants have a finite service life — typically 10–15 years for polyurethane and 15–25 years for silicone — and must be proactively maintained as part of any building's ongoing maintenance programme. Failures arise from age, UV degradation, incorrect joint design, inadequate substrate preparation and the use of incompatible products. Even minor sealant failure can direct significant volumes of water into the building envelope during rain events.
Common Signs
- Cracking through the sealant body (cohesive failure)
- Sealant debonded from one or both joint faces (adhesive failure)
- Gaps, voids or open joints visible on the facade
- Sealant surface chalking, hardening or UV degradation
- Water staining below joint locations after rain
- Mortar or grout in locations that should accommodate movement
- Sealant over-painted, contaminated or bridging across the joint
Common Causes
- Sealant exceeding its service life without maintenance replacement
- Incorrect sealant product selected for the substrate or movement type
- Absent or incorrectly installed backer rod causing three-sided adhesion
- Joint too narrow or too deep for sealant to accommodate movement
- Substrate surface not primed or cleaned before sealant application
- Sealant applied over old sealant rather than fully removed and replaced
- Joint locations at structural junctions filled with rigid mortar
Risk of Neglect
- Water ingress through open facade joints causing internal moisture damage.
- Accelerating substrate deterioration from repeated wetting and drying behind failed joints.
- Corrosion of embedded fixings, ties and reinforcement from moisture penetration.
- Thermal and acoustic performance degradation from open movement joints.
- Mould growth in wall cavities and internal spaces from ongoing moisture ingress.
- Significant cost escalation if joint failure is not addressed before major substrate deterioration.
- Potential strata liability for water damage to lot owner property from failed common property joints.
Inspection Requirements
- Inspect all facade sealant joints including panel joints, window and door perimeters, movement joints and penetration seals for cracking, cohesive or adhesive failure.
- Assess whether sealant failure is cohesive (split through the sealant body) or adhesive (debonded from one or both sides) — different causes and solutions apply.
- Check sealant joint width-to-depth ratio — the correct ratio is 2:1 width to depth; deep, narrow joints prevent adequate sealant movement and cause premature failure.
- Inspect the presence and condition of backer rod — absence of backer rod results in three-sided adhesion and sealant failure.
- Assess whether movement joints are correctly designed and located at structural junctions, material interfaces and at regular centres across panel systems.
- Check for sealant over-painting, surface contamination or priming deficiencies that reduce adhesion life.
- Identify any locations where inflexible materials (mortar, grout or hard caulk) have been used in movement joint locations.
- Test sealant adhesion by pulling an exposed edge — if the sealant pulls cleanly from the substrate without tearing, adhesive failure is confirmed.
Start Inspection Checklist
Create a project inspection record, add defect locations, upload photos, and save notes for scope writing.
Typical Repair Methodology
Sealant replacement requires complete removal of the existing sealant and backer rod — applying new sealant over old sealant is not acceptable and will result in early failure.
- 01.Prepare a joint sealant schedule identifying all joint locations, widths, depths, substrate types and specified sealant products.
- 02.Erect scaffolding or swing stage to provide safe access to all sealant joint locations.
- 03.Remove all existing sealant from the joints to be resealed using a sharp utility knife, oscillating tool or scraper — avoid damaging the substrate face.
- 04.Remove all backer rod remnants and clean the joint faces with solvent to remove all residual sealant, contamination and bond breakers.
- 05.Inspect joint widths and depths before proceeding — joints that are too narrow or too deep may require modification before resealing.
- 06.Install closed-cell polyethylene backer rod at the correct depth to achieve the specified 2:1 sealant width-to-depth ratio.
- 07.Apply masking tape to both sides of the joint to protect adjacent surfaces and ensure clean sealant lines.
- 08.Prime joint faces with the sealant manufacturer's specified primer and allow to dry — primer selection must match the substrate material.
- 09.Apply the specified sealant (polyurethane, silicone or polysulfide) to the joint in a single continuous pass, tooling immediately to ensure full contact with both joint faces.
- 10.Tool the sealant to a concave profile and remove masking tape before the sealant skins.
- 11.Allow sealant to cure for the manufacturer's specified period before exposing to water or traffic.
- 12.Record all joints completed with photographs, product details, batch numbers and joint dimensions.
Related Repair Systems
- Polyurethane facade joint sealant systems
- Silicone structural and facade sealant systems
- Movement joint design and installation systems
- Sealant primer and preparation systems
- Polysulfide expansion joint systems
Open Repair Systems →