Curtain Wall Gasket Replacement and Maintenance

What curtain wall gaskets do, and why they fail

In most stick and unitised curtain wall systems, the glass is held between an inner and an outer gasket and clamped by a pressure plate under a cover cap. Behind that, drained and ventilated channels carry any water that gets past the outer seal back out through drainage slots. When the gaskets fail, water gets into the frame faster than the drainage can cope with it. Common failures include:

• Shrinkage. Rubber gaskets shrink over time and pull back from the corners, opening gaps at the mullion and transom junctions.
• Hardening and cracking. Sunlight, heat and age make gaskets brittle, so they no longer grip the glass.
• Displacement. Gaskets work out of the frame after glass replacement, thermal movement or poor original installation.
• Loose pressure plates. Fixings relax, the clamping force drops and the gasket stops sealing.
• Blocked drainage. Debris in the channels and slots means water that gets in cannot get out.
• Old patch repairs. Sealant smeared over gaskets can trap water and make the next repair harder.

Typical signs include whistling or draughts, water at mullion and transom junctions, staining on internal sills, gaskets visibly hanging out of the frame, and sealed units misting where they have been sitting in water.

How we replace curtain wall gaskets

• Survey and system identification. We inspect sample bays at close quarters, measure and match the gasket profiles, and check the pressure plates, fixings and drainage.
• Trial bay. On larger elevations we refurbish a sample bay first, so you can see the method and the finish before the full programme starts.
• Remove and renew. Capping and pressure plates come off in sequence, the old gaskets are removed, the rebates are cleaned, and new gaskets are fitted with the corners formed as the system requires.
• Re-clamp and drain. Pressure plates are refixed to the correct clamping force, the drainage slots and channels are cleared, and the capping goes back on.
• Test and record. We water test repaired bays where appropriate and keep a photographic record of each elevation.

Cracked glass or failed sealed units found during the work can be replaced on the same programme. See high-level glass replacement.

Planned curtain wall maintenance

Gaskets cost less to maintain than leaks cost to chase. A planned curtain wall maintenance visit typically covers gasket and seal condition, pressure plate fixings, drainage slots, opening vents and ironmongery, perimeter sealant and glass condition, and ends with a prioritised defect list. It can sit inside a wider planned glazing maintenance programme, or alongside façade cleaning so the access is only paid for once.

Access for occupied buildings

We work from rope access, MEWPs and the building's own suspended access where it has it, and from inside where the system is internally glazed. Work is phased bay by bay, so floors stay occupied and the elevation is weathertight at the end of every shift. See rope access glazing.

Gasket replacement or full refurbishment?

If the gaskets are the main problem and the frame, finishes and glass are sound, targeted gasket replacement is usually the most economical fix. Where drainage, fixings, finishes and sealed units are failing together, a wider curtain wall refurbishment is often better value, and we will tell you which at survey. For perimeter and movement joints, see mastic and sealant replacement. For a leak with no obvious cause, start with glazing leak detection.

What we deliver

• Close-quarters curtain wall survey with gasket profiles matched
• Trial bay on larger elevations
• Outer and inner gasket replacement, capping and pressure plate refix
• Drainage slot and channel clearance
• Water testing of repaired bays where appropriate
• Planned curtain wall maintenance visits and defect schedules

How the work is done

Systems	Stick and unitised curtain walling, pressure-plate and capped systems, glazed screens
Typical defects	Shrunk, brittle or displaced gaskets, loose pressure plates, blocked drainage
Sequence	Survey, trial bay, remove and renew, re-clamp, test, record
Access methods	Rope access, MEWP, building suspended access, internal access
Working hours	Daytime, out-of-hours and phased around occupation
Coverage	London HQ, Midlands office in Radcliffe, Nottingham, UK-wide programmes

Questions we get asked