Who this guide is for
- Homeowners planning a new or replacement exterior door
- People who have had water enter at a doorway and want to plan better
- Anyone preparing to brief a door installer or builder
- Owners balancing weather-tightness with accessible thresholds
Why the doorway base is vulnerable
At the threshold, water has the least help from gravity to run away, so wind-driven rain and runoff can pond and find their way in. The detail has to shed water outward while still allowing people to pass over it.
Understanding this tension between weather-tightness and access frames the whole planning conversation.
The sill pan and layered drainage
Beneath the threshold, a sill pan acts as a hidden tray that catches any water that gets past the threshold and directs it back outside, integrated with the wall's weather barrier. The threshold sheds the bulk of the water; the pan is the backup.
You are learning the principle; the pan, flashing and integration are performance-critical professional work.
- A threshold that sheds water outward
- A sill pan as a hidden backup tray
- Drainage that returns water outside
- Integration with the wall's weather barrier
Accessibility versus a raised threshold
A taller threshold keeps water out more easily, while a low or level threshold is easier to walk or wheel over but harder to weatherproof. Planning where your door sits on this trade-off — especially for step-free access — is a key decision.
Capturing your accessibility needs helps a professional balance them with water management.
Exposure and the wider detail
How exposed the door is, whether it is sheltered by a canopy or porch, and how the ground outside drains all affect the threshold detail. A protected door faces less water than one fully exposed to weather.
Noting the door's exposure and what is above and below it helps a professional plan.
Briefing a door installer or builder
Bring your accessibility needs, the door's exposure, and any history of water entry before contacting a door installer or builder.
Let them specify the sill pan, threshold and drainage; your planning keeps the trade-offs clear.
Planning checklist
- 1Understand why the doorway base is vulnerable to water
- 2Learn how the threshold sheds water and the sill pan backs it up
- 3Note your accessibility needs at the threshold
- 4Consider the trade-off between a raised and a level threshold
- 5Note how exposed the door is and any canopy or porch
- 6Observe how the ground outside the door drains
- 7Record any history of water entering at the doorway
- 8Prepare questions on the sill pan and drainage for a professional
Common mistakes to avoid
- Planning the threshold for looks or access without the water detail beneath
- Forgetting the sill pan as the hidden backup against leaks
- Choosing a level threshold without planning how to weatherproof it
- Ignoring the door's exposure and the ground drainage outside
- Assuming the threshold alone keeps water out without a drainage backup
When to involve a professional
- A door installer or builder should specify and fit the sill pan, threshold, flashing and drainage
- Water management at the threshold is performance-critical, so leave the assembly to qualified trades
- For step-free access, balancing weather-tightness and accessibility is a professional design decision
- Threshold detailing varies by door, exposure and location, and a professional should confirm the approach
Frequently asked questions
Questions readers ask about this topic
Why does water get in at the bottom of my door?
The threshold is where water has the least help from gravity to run off, so wind-driven rain and runoff can pond there. A threshold sheds the bulk of the water and a sill pan beneath catches any that gets past, which is why the detail matters.
What is a sill pan?
A sill pan is a hidden tray beneath the threshold that catches water getting past the door and directs it back outside, integrated with the wall's weather barrier. It is the backup behind the threshold and is professional work to fit.
Can I have a level threshold for accessibility?
Level or low thresholds are easier to walk or wheel over but harder to weatherproof, so they need careful detailing. Balancing step-free access with water management is a design decision to make with a professional.
Does a porch or canopy help?
Yes — a sheltered door faces less wind-driven rain than a fully exposed one, which affects the threshold detail. Noting the door's exposure and any canopy helps a professional plan the right approach.
Keep reading