How to Replace an Exterior Door Threshold: 8 Steps That Keep Water Out
To replace exterior door threshold parts the right way you need to do more than swap one strip for another. You remove the old piece and check the sill under it for rot. You fit a new piece that slopes away from the house. Then you seal it so water cannot sneak underneath. Most homeowners finish the job in under two hours with basic tools and about $25 to $50 in materials. A pro charges $100 to $300 for the same work.
Most guides stop at "unscrew it and screw in the new one." That works only if the sill below is sound. This guide adds the parts that other pages skip. You will learn how to tell a threshold from a sill and how to read the damage. You will also see how to measure and how to fix a door that binds after the swap. Use the steps in order and you will not have to do the job twice.
Quick Answer: How to Replace an Exterior Door Threshold
Here is the whole job in eight lines. Each step gets its own section below.
- Diagnose. Find out whether you need a new threshold or a new sill.
- Pick the type. Match the material and height to your door.
- Measure. Check the width between the jambs and the depth of the sill.
- Remove the old threshold. Cut it in two if it is stuck.
- Check the sill. Probe for rot and dry it out or repair it.
- Fit the new threshold. Cut it to size and test it in place.
- Seal and fasten. Caulk the underside and drive the screws without overtightening.
- Adjust the door. Set the sweep or bottom seal so the door closes tight.
Threshold or Sill: Know What You Are Replacing
People use the words as if they meant the same thing. They do not. Angi explains the difference clearly. The sill is the structural base of the doorframe. It rests on the foundation or porch deck or slab. The threshold sits on top of the sill between the door jambs. It slopes to drain water away from the door. Angi calls the threshold the first line of defense against the elements.
That difference decides your repair.
- Worn or cracked threshold with a sound sill below. Replace only the threshold. This is the job in this guide.
- Soft or rotted sill. The sill needs repair or replacement first. A new threshold on a bad sill fails in a season or two.
- Daylight showing under the door. The sweep or the threshold height may be off. You may not need a new threshold at all.
Signs Your Threshold Needs Replacing
You do not need a new threshold every time a door sticks. Look for these signs.
- Cracks or splits in a wood threshold
- A metal threshold that is bent or dented
- Rust or corrosion on the aluminum
- Water pooling inside the door after rain
- A draft you can feel on your ankles
- Daylight under the door with the door closed
- A rubber insert that is torn or missing
- Loose screws that will not hold
- A soft spot when you press with a screwdriver
If the wood feels soft or crumbles the damage may reach the sill. Check before you buy anything.
Step 1: Diagnose Before You Buy
Close the door and look at the bottom edge from inside. Turn off the lights if you can. Light leaking under the door means the seal has failed. The cause may be the sweep and not the threshold.
Then press a flat screwdriver into the wood at the corners of the threshold and into the sill if you can see it. Sound wood resists. Rotted wood gives way. Check the spots where water collects such as the ends near the jambs.
Angi advises you to check the frame and subfloor for rot or damage after you remove the old threshold. Do this early so you buy the right parts.
Step 2: Pick the Right Threshold Type
Thresholds come in a few common materials. Each has trade-offs.
| Type | Strengths | Weak points | Best for |
|---|---|---|---|
| Oak or hardwood | Classic look and sturdy | Can rot if not sealed | Painted or stained wood doors |
| Extruded aluminum | Resists rot and lasts long | Can dent and conduct cold | Most entry doors |
| Adjustable aluminum | Sets height with screws | Costs more | Doors with uneven gaps |
| Composite or fiberglass | Will not rot | May cost more | Wet or coastal areas |
HomeTips notes that classic thresholds are made of durable hardwoods such as oak and that newer ones are extruded aluminum including adjustable models. Home Depot lists exterior thresholds in wood or metal.
Check three things before you buy.
- Width. It must match the opening between the jambs.
- Depth. It must cover the sill and tuck under the door.
- Height. It must clear the door bottom and the floor inside.
Take the old threshold to the store if you can. Match the profile.
Step 3: Measure Twice
Home Depot says to measure the opening between the outside edges of the door casing. Mark the new threshold at that length. Many exterior thresholds need notches so the ends fit around the jambs.
Use this checklist.
- Measure the width at the front edge and the back edge. Doorframes are rarely square.
- Measure the depth from the outside edge of the sill to the inside floor.
- Measure the height of the door bottom above the sill.
- Write the numbers down before you cut.
Angi notes that exterior thresholds usually need only one straight cut. Notches are more common on interior pieces. Check your own piece against the old one.
Tools and Materials You Will Need
Gather everything before you start. Angi and Home Depot list similar items.
Tools
- Pry bar and putty knife
- Tape measure and pencil
- Hacksaw or tin snips for metal or a handsaw for wood
- Jigsaw or reciprocating saw if the old piece is stuck
- Drill and bits
- Screwdriver
- Caulk gun
- Rubber mallet
- Plane for trimming a wood piece that binds
Materials
- New threshold
- Exterior sealant caulk
- Screws that suit the threshold
- Construction adhesive if the new threshold calls for it
- Replacement door sweep or gasket if yours is worn
Safety
- Safety glasses
- Work gloves
- Dust mask when you cut or sand
Metal cuts leave sharp edges. Wear gloves and file the cut ends smooth.
Step 4: Remove the Old Threshold
Open the door fully. If you can lift the door off its hinges the work is easier. Many people leave it hung and work around it.
- Strip off any trim or old sealant. Run a putty knife along the edges.
- Remove the screws from an exterior threshold. Home Depot says to cut the old one out with a back saw or reciprocating saw and then pry the pieces loose if it is stuck.
- Cut a stuck piece in the middle. Pull each half out toward the center.
- Pull out nails or screws left in the sill.
- Scrape off old caulk and adhesive.
Take care not to saw into the flooring. Home Depot warns about this. Angi advises you to use a putty knife and pry bar carefully to avoid damaging the flooring.
Step 5: Check and Repair the Sill
This is the step most guides skip. A new threshold on a wet sill will trap moisture. Clean the area. Sweep out the dust. Probe the sill with a screwdriver in several spots.
If the sill is dry and sound: Wipe it clean and let it dry. Move to the next step.
If the sill is damp but sound: Find the water source first. A leaking door bottom or a gutter that drains at the door may be the cause. Dry the wood fully before you install anything.
If the wood is soft in a small area: Surface rot can often be dug out and repaired with a wood filler made for exterior use. Follow the product directions. Let it cure fully.
If the sill is rotted through or crumbling: The sill must be replaced. This is a larger job that may include cutting out the damaged section and fitting a new piece. Angi describes the process in broad terms. You remove the threshold and cut out the damaged sill and then notch and fit a new one. If the rot reaches the framing or the subfloor call a carpenter.
HomeTips notes that replacing is usually better than repairing rotted woodwork because it is easier and lasts longer. Judge by how far the damage goes.
Do not skip this step. A threshold that sits on rot will fail again.
Step 6: Dry-Fit the New Threshold
Place the new threshold on the sill without caulk. Check the fit.
- Does it sit flat with no rocking?
- Does it slide under the door stops?
- Does the front edge slope away from the house?
- Does the door clear the top of the threshold?
Home Depot says the threshold should slope slightly away from the house so water does not pool at the doorway. A level or flat threshold holds water against the door.
If a wood piece binds under the door use a plane to trim it. Take off a little at a time. Remove material from the top edge and not the bottom. If an aluminum piece is too high use an adjustable model or a lower profile.
Mark the final position with pencil.
Step 7: Seal and Fasten
A good seal keeps water out and a poor one invites rot. Follow this order.
- Lift the threshold out.
- Run a continuous bead of exterior sealant on the sill along the back edge and under where the threshold will sit. HomeTips suggests silicone caulk. Home Depot says to caulk the back edge.
- Set the threshold back into position.
- Press down firmly so the sealant spreads.
- Drive the screws. Angi says exterior pieces are screwed down and warns against overtightening the screws.
- Countersink the screws so the heads sit flush. HomeTips advises countersunk screws.
- Caulk where the threshold meets each door stop and jamb.
- Wipe away excess caulk with a damp cloth.
Angi advises letting the caulk cure for 24 to 48 hours before heavy use. Avoid washing the area or slamming the door during that time.
Use screws made for the material. Stainless or coated screws resist rust. Aluminum thresholds often come with their own screws.
Step 8: Adjust the Door Sweep and Test the Seal
A new threshold changes the gap at the bottom of the door. The sweep or door bottom may need adjusting.
- Close the door and check the gap with a piece of paper. The paper should drag slightly.
- Look for daylight under the door.
- Adjust an adjustable threshold with the set screws.
- Replace a worn sweep or gasket. HomeTips says new gaskets usually press into a groove. Buy an exact replacement.
- Check that the door latches without force.
Do a water test. Run a hose gently along the base of the door from outside. Check inside for any water after five minutes. Look at the corners.
If the door binds or sags after the swap you may have a hinge problem. Our guide on how to fix a sagging door walks through hinge and frame fixes.
How Long Does It Take to Replace an Exterior Door Threshold?
Angi says about 30 minutes of work in its table and under an hour in the intro. Home Depot rates the job at under two hours and intermediate skill. Plan for one to two hours the first time. A stuck piece or a rotted sill adds time. Caulk needs 24 to 48 hours to cure.
Cost to Replace an Exterior Door Threshold
Costs are low. These numbers come from Angi.
| Item | Cost |
|---|---|
| DIY materials | $25 to $50 |
| Pro labor and materials | $100 to $300 |
| Typical DIY savings | $100 to $300 |
Angi says exterior jobs cost more than interior ones because they need waterproofing and weatherproofing. Marble bathroom thresholds are among the most expensive.
Extra costs show up if you find damage. A rotted sill or damaged framing costs more to fix. Angi does not give a price for sill repair and neither do the other pages we reviewed. Get a written quote from a carpenter if you find rot. For a wider view of project costs see our home renovation cost guide.
DIY or Hire a Pro?
Most people can do this job. It is rated intermediate but needs only hand tools. Hire a pro in these cases.
- The sill is rotted through
- The frame is out of square
- You are unsure you can waterproof the joint
- The door is a heavy steel or fire-rated unit
- The threshold is marble or tile
Angi recommends a handyman for marble thresholds and for exterior work if you doubt your waterproofing. Our DIY home improvement guide shows which jobs a careful beginner can do.
Common Mistakes When You Replace an Exterior Door Threshold
These errors cause most failures.
- Skipping the sill check. Rot under a new threshold keeps spreading.
- Using too little sealant. Water finds the smallest gap.
- Installing it flat or sloped toward the house. Water runs inside.
- Overtightening screws. Angi warns against this. It can crack the threshold or bow it.
- Forgetting the door sweep. The old sweep may not match the new height.
- Cutting into the flooring. Use a pry bar with care.
- Using interior caulk outside. Pick exterior sealant.
- Rushing the cure time. Give caulk the full 24 to 48 hours.
When the Draft Continues After the Swap
Sometimes a new threshold does not stop air. Check these causes.
- The weatherstripping on the jambs is worn.
- The door slab is warped.
- The sweep is the wrong size.
- The threshold is set too high or too low for the door.
- Gaps remain at the ends where the threshold meets the jamb.
Re-caulk the ends and replace the weatherstripping first. Our guide on how to reseal windows covers the same sealing basics and our page on how long caulk takes to dry helps you plan the cure.
Threshold Care for a Small or Tiny Home
Small homes and tiny houses often have a single exterior door. A failed threshold lets water into a small floor area fast. Many tiny homes sit on trailers or piers where wind and rain hit the door hard. Check the threshold each spring and fall. Reseal the ends if the caulk cracks. If you are planning a compact home our tiny house cost guide shows how small repairs fit a yearly budget.
Frequently Asked Questions
How do I replace an exterior door threshold?
Remove the old threshold and check the sill for rot. Cut the new piece to length and test the fit. Seal the underside with exterior caulk and screw it down without overtightening. Then adjust the sweep and test the seal.
How much does it cost to replace an exterior door threshold?
Angi lists $25 to $50 in materials for DIY and $100 to $300 for a pro. Exterior jobs cost more than interior ones because of waterproofing.
How long does it take to replace an exterior door threshold?
Plan for one to two hours. Angi lists about 30 minutes to under an hour of work. Home Depot says under two hours. Caulk needs 24 to 48 hours to cure.
What is the difference between a door sill and a threshold?
The sill is the structural base of the doorframe. The threshold sits on top of it and slopes to drain water away. Angi explains this difference.
Do I need to remove the door to replace the threshold?
Not always. You can work around a hung door. Removing it gives more room and makes it easier to cut and fit the piece.
Which direction should the threshold slope?
It should slope slightly away from the house so water drains outward. Home Depot gives this advice.
What should I do if the sill is rotted?
Dig out small soft areas and repair them with exterior wood filler. Replace the sill if the rot goes deep. Call a carpenter if the framing or subfloor is damaged.
Why does my door still leak after a new threshold?
Check the sweep and the weatherstripping. Check the gaps at the ends of the threshold. Make sure the threshold slopes away from the house and is sealed on the underside.
Final Thoughts on How to Replace an Exterior Door Threshold
To replace exterior door threshold parts well you need to look below the surface. Check the sill. Fit the new piece with a slope away from the house. Seal it well and give the caulk time to cure. Most people finish in an afternoon for $25 to $50.
Do the sill check and the water test. They take ten minutes and save you from redoing the work. If you find deep rot or a frame that is out of square bring in a carpenter.
Thinking of replacing the whole door instead? See the door replacement cost for entry and patio doors.
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