Door Sill vs. Threshold: What’s the Real Difference?

Are you trying to fix a drafty door but confused by “sill” vs “threshold”? You’re not alone.

This guide provides a clear, visual explanation, enabling you to diagnose issues, purchase the appropriate parts, and approach the project with confidence.

What’s at the Bottom of a Door? (Anatomy Diagram)

From the subfloor up, you’ll identify the sill (the foundation of the frame), the threshold (the sealing cap), the door panel with a sweep, and the jambs on the sides.

Key parts in a right-to-left, cross‑section view:

• Subfloor
• Door Sill — “The Foundation” of the door frame; may be wood, composite, or integrated with a sill pan
• Door Threshold—The seal that sits on top of the sill; adjustable or fixed
• Door Panel & Door Sweep—The sweep compresses on the threshold to block drafts/water
• Door Jambs—Vertical frame members that meet the sill at the bottom corners

How Do “Sill” and “Threshold” Compare?

The sill is a structural frame member; the threshold is a replaceable wear-and-seal surface.

Do Interior Doors Have Sills?

No—interior doors typically do not have a sill. What you see on the floor is a threshold or transition strip.

• Interior doors: The strip between rooms (e.g., bathroom tile to hallway wood) is a threshold/transition, not a sill.
• Materials vary: wood, marble/stone, or metal. Its jobs are level change, finish transition, and a minimal draft barrier (not weatherproofing).

Why Does the Distinction Matter for Homeowners?

It determines what you replace, how much it costs, and who should do the work.

• Diagnosing Problems
  • Soft, spongy wood under the threshold? Likely a rotted sill (serious; investigate leaks and flashing).
  • Visible dents, loose screws, or poor contact with the door sweep? Likely the threshold (simple fix or adjustment).
• Purchasing Parts
  • Draft under the door? Start with an adjustable threshold or replace the worn one. Also inspect the door sweep and weatherstripping.
  • Sill components are typically part of the door unit; you rarely buy a “sill” alone unless rebuilding the frame.
• Project Scope
  • Replace threshold: ~1 hour DIY with basic tools.
  • Replace sill: Advanced job—often involves removing the door unit, adding a sill pan, and reframing. Hire an experienced contractor.

Pro tip: If you observe moisture damage, add or upgrade a sill pan flashing to protect the new sill and threshold from future leaks.

Mini decision flow:

1. Draft only when the door is closed. → Adjust or replace the threshold and door sweep.
2. Water staining or softness at corners → Inspect sill and flashing; plan a pro repair.
3. Threshold screws are maxed out, but there is still a gap. → Replace the threshold with a taller/adjustable model; confirm the sweep condition.

What Types of Replacement Thresholds Can You Buy?

Most homeowners choose between a simple saddle, a bumper‑seal style for tighter closure, or an adjustable threshold for a perfect fit.

• Saddle Threshold
  • A solid, gently arched profile.
  • Best for durability and simplicity; fewer parts to fail.
• Bumper Seal Threshold
  • Adds a raised vinyl or rubber “bumper” that the door face presses against.
  • Great for an improved air/water seal.
• Adjustable Threshold
  • Features screws to raise/lower the cap to meet the door sweep perfectly despite settling.
  • Ideal for stopping drafts without rehanging the door.

Tip: Pair a new threshold with a fresh door sweep for the best seal. Confirm outswing vs. inswing orientation before buying.

Conclusion: Now You’re the Expert

The sill is the structural base of the door frame; the threshold is the replaceable sealing cap you walk over. With the right vocabulary, you can diagnose issues faster and buy the correct parts.

Next step: Is your threshold worn out? Follow our step‑by‑step tutorial: How to Replace a Door Threshold.