Curtain walling is a specialist system. It is designed, supplied and installed by specialist contractors, and questions about the system itself belong with them. Around it, though, there are sealant joints that building owners and facilities teams still need to understand. This is a general guide to those joints. It is not advice on designing, installing or repairing a curtain wall.
Where sealant sits on a glazed facade
On most glazed facades, sealant appears in a few places:
- perimeter joints, where the frame meets the surrounding structure
- joints at copings, sills and flashings where sealant is the specified fix
- interfaces with other cladding, brickwork or render
- joints within the system itself, which are the system supplier’s responsibility
The perimeter joint is the one owners most often deal with in maintenance. It closes the gap between two different elements that move in different ways.
Why perimeter joints work hard
A glazed facade and the frame of a building expand and contract at different rates. Aluminium, glass, concrete and steel all respond differently to heat and sunlight. The perimeter joint has to take that movement every day. It also faces rain, wind pressure and ultraviolet light. Joint width must suit the expected movement and the movement capability of the sealant, and the depth is usually controlled with a backing rod. Our guide to joint width, depth and backing explains why this matters.
Compatibility matters
Sealants used near glazing have to be compatible with the materials they touch. That includes gaskets, insulating glass unit edge seals, coatings and other sealants. An incompatible product can stain, soften or break down a neighbouring material. Acetoxy silicones, the ones that smell of vinegar as they cure, can attack some metals and stone, so neutral-cure sealants are normally used on building joints. If a joint sits close to the system, check with the curtain wall supplier before choosing a product. Many specifications refer to BS EN 15651, which has separate parts for facade and glazing sealants (see BS EN 15651 in plain English).
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Signs worth reporting
From the ground, from inside, or from a window cleaning cradle, look for:
- sealant that has pulled away from one face of the joint
- splits running along the middle of the bead
- chalky, hard or cracked surfaces on sunny elevations
- staining on glass or stone below a joint
- water marks on internal finishes near the frame
Our guide to sealant failure types helps you describe what you are seeing. Leaks at frames can come from several sources, so a wet reveal does not always mean the sealant is at fault.
Who to call for what
Keep roles clear. Issues with glazing units, gaskets, internal drainage or the system’s own seals go to the curtain wall supplier or a specialist facade contractor. Sealant joints where frames meet the structure are a more general sealant task. Our facade and window perimeter sealing work covers those perimeter joints. It does not include curtain wall installation or structural glazing. If you’re unsure which side of that line a problem falls, send photos and we’ll say whether it is something we can help with.
Records worth keeping
Keep the facade’s O&M information, including product data sheets for any perimeter sealants and the system supplier’s maintenance guidance. When a joint is resealed, record the product, colour and date. That history helps whoever looks at the facade next to choose a compatible product.
Quick answers
Can perimeter sealant be replaced without touching the curtain wall?
Often, yes, where the perimeter joint is a separate seal between the frame and the structure. The old sealant is cut out, the faces are prepared and a compatible sealant is installed. If the joint forms part of the system’s weather line, involve the system supplier first.
How often should facade joints be inspected?
There is no single interval. It depends on exposure, orientation, the product and the building’s history. Many owners include facade joints in a planned inspection cycle and look again after storms or any reported leak.
Does access affect the work?
Yes. Facade joints are often at height, and the access method has a big effect on planning and cost. Tell us what access the building already has, such as cradles or anchor points, when you ask for a quote.
Related services
More advice
- Leaks Around Windows on Commercial Buildings
- Sealant Joint Design: Width, Depth and Backing
- BS EN 15651 Sealant Classes in Plain English
- Adhesive, Cohesive and Substrate Sealant Failure
- All advice
This guide is general information about sealant work. It isn’t legal, fire-safety or structural advice; for those, speak to a qualified professional.