In lightweight façade or curtain wall systems, watertightness depends both on the design of the aluminium profile and the accompanying rubber seal. A correctly sized and positioned seal ensures that water, air and noise are kept out, even in the most demanding conditions.
In this article, we will look at how joint geometry, seal compression and drainage channels work together to achieve a watertight and durable façade.
The role of rubber seals in curtain walls
Rubber seals for aluminium windows not only seal the joint between the glass and the profile: they are also responsible for absorbing tolerances, cushioning expansion and conducting water to the outside.
In a curtain wall, the aluminium profile is designed to support the glass without direct contact. The seal is placed between the two, acting as a flexible layer of waterproofing and cushioning. In this way, the assembly withstands thermal movements and vibrations without compromising airtightness or aesthetics.
The most commonly used material is EPDM, due to its excellent resistance to UV rays, rain and temperature changes. There are also co-extruded TPE gaskets, which combine a rigid body and flexible lip for faster installation and uniform closing pressure.
Gasket geometry: more than just rubber
Each type of gasket is designed for a specific function. Three types are mainly used in curtain walls:
- Inner compression gaskets: seal between the glass and the profile from the inside. They compress to absorb tolerances and prevent air leaks.
- External contact gaskets: create the initial barrier against rainwater. Their external lip directs water towards the drainage channels.
- Intermediate or co-extruded gaskets: combine several functions, facilitating assembly and improving durability.
The correct lip geometry and hardness are key. A seal that is too soft will not maintain the necessary pressure; one that is too rigid will prevent the glass from fitting properly and could cause leaks.
Drainage and water pressure
A good lightweight façade design does not attempt to block water 100%, but rather to control its flow. For this reason, the profiles incorporate channels and holes that allow accumulated water to drain to the outside.
The joints help to direct this flow. The outer lip acts as a deflector, while the space between the joints forms a pressure chamber that balances the air and prevents water from penetrating through capillary action.
In this way, even under heavy rain or wind pressure, the system remains watertight and allows water to drain away without seeping inside.
Assembly and tolerances of glass and profile
The correct assembly of the seals is as important as their design. Before installation, the following must be checked:
- Tolerance between glass and profile: this must allow for the correct compression of the seal.
- Cleanliness and alignment: any dust or adhesive residue can prevent a good fit.
- Mitre cut and continuity: the corners must join without gaps or tension.
Poor installation, for example, a stretched seal or a dirty channel, can ruin the entire sealing job, even with top-quality materials.
Materials and maintenance
Rubber seals for aluminium window glass made of EPDM or TPE offer long life and stability against UV rays. It is recommended to check their condition periodically, especially in areas that are highly exposed to the sun or rain.
If the rubber has hardened, cracked or turned white, it is time to replace it. Replacing it in time prevents leaks and maintains the thermal and acoustic performance of the curtain wall.
> More info on gaskets for aluminium windows.
> More info on gaskets for taps.
Do you need rubber seals for your project?
At ISOGOM, we manufacture and extrude rubber seals for aluminium windows and curtain walls adapted to each profile and construction system. We offer solutions in EPDM and TPE with customised geometries, technical advice and quality control throughout the process.
