What Is a Threshold?
A threshold is the horizontal piece at the bottom of an exterior door opening. It supports the door seal, helps block drafts and directs water away from the doorway. A threshold may be made from metal, wood or another durable material. Its height and slope must fit the door, floor and surrounding weatherproofing.
Quick Facts About Threshold
Category
Exterior door component
Used for
Sealing and supporting a doorway
Common confusion
Often confused with the door jamb
Also called
Door Sill, Sill
Often discussed with
Exterior Door Installation
Key Takeaways About Threshold
- The threshold sits beneath the exterior door.
- A sloped surface helps move water away.
- A threshold is not the same as a door jamb.
How Threshold Works
A threshold rests across the bottom of an exterior door opening. The door sweep or bottom seal presses against it when the door closes. This contact limits air movement and helps keep rain from entering beneath the door.
Related glossary terms: Door Jamb, Flashing, Rough Opening.
The threshold must meet the door frame, flooring and exterior surface at the right level. A sloped top sheds water outward. Adjustable parts can help create a close seal when the floor or door sits slightly uneven. The door jamb rises on each side and supports the door, while the threshold spans between the jambs.
Thresholds on Exterior Doors
- Metal thresholds resist wear at busy entry doors.
- Wood thresholds may match a wood door system.
- Sealant closes small gaps along the threshold edges.
Expert Note
When we install an exterior door, we check the threshold against the rough opening, finished floor and door sweep. We also check the slope and edge seals so water can move away from the doorway instead of collecting beneath it.
Threshold in Practice: A Real-World Example
For a new exterior door, the threshold sits across the sill and meets the finished flooring inside. The installer adjusts the seal so the closed door blocks drafts without rubbing against the threshold.
Related Services
Related Terms
Door Jamb
A door jamb is the vertical and horizontal frame that surrounds a doorway and supports the…
Flashing
Flashing is a thin, shaped material that directs water away from roof joints, wall edges, chimneys…
Rough Opening
A rough opening is the framed space in a wall that receives a window or door…
Caulking
Caulking is a flexible sealant applied to joints and gaps around building materials. It blocks drafts…
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