Horizontal Radius

The horizontal radius is the bent section of track that forms the curve between the vertical track and the horizontal track on a sectional garage door. The door panels travel straight up the vertical track alongside the opening. Then they curve through the radius and lay flat in the horizontal track overhead. The horizontal radius is the transition between those two travel paths.

This curved piece is attached to the horizontal track at the factory or in the field. It bolts to the flag bracket at the top of the vertical track. Together, the vertical track, horizontal radius, and horizontal track form a continuous guide path for the door rollers.

How radius size affects installation:

The radius size, measured in inches, determines how much headroom the door requires above the opening. A 12-inch radius needs less vertical space than a 15-inch radius. A 15-inch radius allows a smoother, gentler bend. That matters for heavy commercial doors where a tight bend stresses the panels.

Standard residential track uses a 12-inch radius. Low-headroom situations sometimes require a modified horizontal radius that keeps the track closer to the header, or a different hardware package altogether. High-lift track extends the vertical sections higher before the curve, pushing the horizontal track up toward the ceiling.

For example, a standard garage with 12 inches of headroom above the door opening uses a 12-inch radius. The door clears the opening and lays horizontal within that 12 inches of space. A 15-inch radius on the same garage would need at least 3 more inches of headroom clearance.

The horizontal radius is sometimes called the track radius. The terms are used interchangeably in the field.