Fillet Sealant Beads. Putting Mother Nature in a Corner.

OSI proper fillet sealant bead

 

Keeping Mother Nature out of your building envelope requires knowing how its many components function and how to use them. A simple bead of sealant, for example, can be the critical first line of defense in vulnerable areas such as right angle corners. Here, Paul Majka, OSI Application Engineer, takes us on a deep dive into the fillet bead.

 

What are the most common mistakes people make with fillet beads?

Many people are not aware how critical the proper application is for a fillet bead. And the three most common mistakes they make are 1) too small a bead, 2) unbalanced beads and 3) overtooled beads. To effectively seal a right angle corner, a fillet bead has to be at least ⅜” and balanced evenly on each face of the angle. Make the bead to small or apply too much sealant to one side or the other and you create a weak seal. And overtooling simply removes too much sealant from the joint and weakens its ability to perform.

 

When do you use a fillet bead?

You use a fillet bead in a fillet joint, which is formed when two surfaces come together to form a right angle. Sealant is applied to this joint to join the two surfaces in a triangular shape.

 

What makes it a good solution for right angle joints?  

It’s actually the only solution for right angle joint designs. When applied correctly, a fillet bead will withstand the demands of joint movement and adhesion against the cyclical pressures of sun, wind, water, snow and ice. It becomes the primary seal to protect against these elements and provide durability and longevity for the building envelope.

 

 

OSI fillet bead sealant siding installation

 

How do you know you’re looking at a good fillet bead?

A fillet bead is triangular in shape and should be applied to a specific dimension—3/8” wide, ¼” deep on both sides of the joint and 1/8” inch center depth.

  

What's the best way to apply a fillet bead?

Cut the sealant cartridge or tube nozzle at a 45°-degree angle. The nozzle should be cut to expose a 3/8” inch opening. The nozzle is then centered in the right angle joint and sealant is dispensed over the gap and against both surfaces. It’s important that the dispensing of the sealant and movement of the gun are balanced to apply a consistent bead along the length of the joint.

  

How do weather conditions affect it?

If sealant is applied correctly to the fillet joint, the sealant will perform no matter how severe the weather conditions. It will  deliver the required performance against extensive UV, water and wind exposures sustain joint movement capability needed.

 

Learn more about proper sealant application. Get our Best Practice Guide