Spotted These Yellow Circles in a Wall? Here’s What They Actually Do
March 24, 2025
source: Spectrum Concrete USA
When you walk past a construction site or a freshly built concrete wall, you might notice something odd—small yellow plastic circles embedded in the surface. These little discs often catch the eye, especially if you don’t know what they’re for. It turns out they’re part of a construction tool called a plastic snap tie for concrete forms, and they serve an important purpose.
What Is a Plastic Snap Tie?
A plastic snap tie is a fastener used during concrete construction. It holds formwork—temporary molds—in place while workers pour the concrete. The yellow piece that remains visible is the end of this snap tie system.
Concrete can’t support itself when it’s still wet. To give it shape, builders use forms made of wood or metal. Snap ties connect these form panels and keep them from spreading apart under the pressure of the concrete.
What’s the Deal With the Yellow Circle?
The circle is usually called a cone or end cap. It stays behind after the rest of the tie is removed. These cones do several things:
- Act as spacers: They help keep a uniform distance between the form panels, which controls the wall’s thickness.
- Seal holes: They block water and moisture from entering where the metal tie once sat.
- Mark positions: Their bright color makes it easy to find the tie points during finishing work.
How Do Snap Ties Work?
Here’s how the process typically goes:
- Builders set up the wooden or metal forms on both sides of the wall area.
- They insert snap ties through the forms. The yellow ends stick out on both sides.
- Workers pour wet concrete into the space between the forms.
- Once the concrete sets, they snap off the exposed metal part of the tie, leaving the plastic ends behind.
What’s left is a small, round plastic circle flush with the wall surface—neatly spaced and clean-looking.
Do the Yellow Circles Serve Any Purpose Later?
Mostly, their job ends once the concrete cures. However, they also plug the holes where the tie passed through, which helps protect the wall from moisture. In some cases, crews remove the caps and patch the holes, especially for aesthetic or waterproofing reasons. Often though, they leave them in place since they don’t affect the structure.
A Small but Mighty Piece of Construction
These snap tie ends might seem insignificant, but they quietly play a vital role in the early stages of construction. They help shape concrete walls, hold forms in place, and keep everything aligned. Once the job is done, they remain as subtle signs of the work beneath the surface.
So next time you or your child spots those yellow circles in a wall, you’ll know you’re looking at a plastic snap tie for concrete forms. It’s a small reminder of the hidden systems that keep our structures strong and solid.