How to Replace a Door Threshold in 9 Steps

How to Replace a Door Threshold in 9 Steps

Replacing a door threshold is a manageable DIY project that can be completed in approximately two hours, making it an accessible task for homeowners with moderate skill levels. A door threshold serves as a critical barrier between your home’s interior and exterior, protecting against water infiltration, drafts, and pest entry. Over time, thresholds can become damaged, rotted, or warped, necessitating replacement. This comprehensive guide walks you through each step of the threshold replacement process, from initial measurement to final sealing.

Project Overview and Requirements

Before beginning your threshold replacement project, it’s important to understand the scope and requirements involved. This project is rated as moderate difficulty, requiring some skill to properly measure and match the old threshold’s shape on the new one. The estimated cost for materials typically ranges from $70 to $100, depending on the threshold material and dimensions. However, the actual time investment can vary significantly if underlying structural issues are discovered during the removal process.

Timing Considerations

It’s advisable to start replacement work early in the day to allow sufficient time for addressing any problems that may emerge once the old threshold is removed. A seemingly straightforward two-hour project can extend into a full day’s labor if you encounter a rotten subsill, punky joist ends, or a termite-riddled rim joist. These underlying structural issues must be addressed before installing the new threshold to ensure long-term durability and prevent future damage.

Essential Tools and Materials

Gather the following tools before beginning:

– Reciprocating saw with wood-cutting blade (at least as long as the old threshold is deep)- Flat pry bar (also called a pry bar)- Hammer and chisel- Jigsaw or circular saw- Handsaw- Square (framing or combination square)- Measuring tape- Rubber mats or knee pads- 120-grit sandpaper- Cedar shingles for shims- Expanding foam sealant- Borate solution (such as Bora-Care)- Deck paint or spar varnish- Wood block

Step-by-Step Threshold Replacement Process

Step 1: Prepare Your Work Area

Begin by removing the storm door and any weatherstripping attached to the threshold. You’ll spend considerable time kneeling on the outside of the house during this project, so prepare your work area by placing rubber mats on the porch or investing in a quality pair of knee pads. This preparation protects your knees and makes the extended work period more comfortable.

Step 2: Measure and Prepare Replacement

Accurately measuring the old threshold is crucial for selecting the correct replacement. Measure the length, width, and thickness of the existing threshold and have a replacement with a similar profile ready before beginning removal. The new threshold should be approximately one to two inches longer than the distance between the door casing’s outside edges. This extra length allows you to trim it for an exact fit after installation.

Step 3: Remove the Old Threshold

With your reciprocating saw equipped with a wood-cutting blade at least as long as the old threshold is deep, slice across the wood in two places, approximately ten inches from each jamb. Hold the blade so its teeth are nearly parallel to the surface, carefully watching the blade’s tip to avoid cutting the flooring. Stop sawing as soon as you feel the blade cut through the threshold. Allow the blade to stop moving completely before lifting the saw from the kerf to prevent splintering.

Step 4: Pry Out the Exterior Board

Insert a flat pry bar between the threshold and the subsill, then carefully pry upward on the center section. If possible, wiggle the ends away from the jambs, or split them with a hammer and chisel, removing them piece by piece. Exercise patience and finesse throughout this step rather than using brute force, as aggressive removal can damage the door stops at each end.

Step 5: Inspect and Treat the Subsill

Pry off the toekick, which is the exterior board below the threshold, and thoroughly probe the wood underneath for signs of decay. If you discover any rotten wood, it must be replaced before proceeding. Once any damaged wood is addressed, spray the entire subsill area with a borate solution like Bora-Care to prevent future rot and repel termites. This treatment is essential for protecting your home’s structural integrity.

Step 6: Lay Out the Notch for the New Threshold

The ends of the new threshold must be notched to fit around both door jambs, creating a “horn” that extends under the casing. First, measure the width of the right-hand casing. Hook your measuring tape on the threshold’s back right-hand corner and transfer that measurement to the threshold’s back edge. Next, measure the width of the jamb and stop, hook the tape on the same corner, and transfer this measurement to the end of the stock. Use a square to draw perpendicular lines from each mark until the lines intersect, creating your cut line.

Step 7: Cut Out the Notches

Cut along the layout lines using a jigsaw or circular saw. If using a circular saw, finish the cuts with a handsaw for precision. To mark the cuts for the left-hand notch, measure the width of the opening from jamb to jamb, then hook the tape on the cut-out notch and transfer that measurement to the threshold’s back edge. Mark the width of the jamb and stop on the threshold’s left end, join the marks with a square, and cut out this notch as well.

Once both notches are cut, trim the horns flush with the edges of the casing. Sand the threshold with 120-grit paper and spray it with borate solution to provide protection before installation.

Step 8: Install the Threshold

Slip the notched threshold into position under the door stops, then carefully nudge it into place by tapping a hammer against a wood block pressed against the threshold’s edge. Change the block’s position regularly so neither end of the threshold advances too far ahead of the other. When the threshold is tight to the subfloor, slide pairs of cedar shingle shims under the center and both ends of the threshold, but not under the horns. Arrange the shims so the thin end of one rests on the fat end of the other. This arrangement allows you to tap on the fat end and lift the threshold without tilting it.

When the threshold is tight against the door stops and casing, snap the shim ends off flush with the subsill using a hammer and chisel.

Step 9: Seal with Foam and Finish

Squirt expanding foam sealant under the threshold to hold it in place and plug any remaining air gaps. Immediately reinstall the toekick under the flashing, pressing it tight against the underside of the threshold, then screw it to the subsill. Run a bead of sealant between the threshold and each door stop to prevent water infiltration. Finally, protect the wood by applying deck paint or several coats of spar varnish for long-lasting weather protection.

Essential Tips for Success

Protect Your Knees: Invest in quality knee pads or use rubber mats to protect your knees during this kneeling-intensive project.

Check for Underlying Damage: Always inspect the subsill, joists, and surrounding wood for rot or termite damage before installing the new threshold.

Use Proper Shims: Cedar shingle shims are ideal for threshold installation as they can be easily tapped into place and trimmed flush.

Be Patient with Removal: Avoid aggressive removal techniques that could damage door stops or surrounding trim.

Seal Thoroughly: Proper sealing with expanding foam and caulk is crucial for preventing water infiltration and maintaining energy efficiency.

Common Issues and Solutions

Frequently Asked Questions About Threshold Replacement

Q: How long does threshold replacement typically take?

A: Most threshold replacements can be completed in approximately two hours, though discovering structural issues like rot or termite damage can extend the project to a full day.

Q: Can I install a new threshold over the old one?

A: It’s not recommended to install a new threshold directly over the old one, as this can create uneven surfaces and drainage issues. The old threshold should be completely removed and the subsill inspected before installing the new threshold.

Q: What type of wood is best for a replacement threshold?

A: Oak and hardwood thresholds are popular choices due to their durability and resistance to wear. The replacement threshold should match the profile of the original for proper fit and function.

Q: Should I use expanding foam or caulk for sealing?

A: Both are important. Expanding foam is used under the threshold to hold it in place and seal large gaps, while caulk is used around the edges where the threshold meets the door stops and casing for a finished appearance and additional weather protection.

Q: What is a door threshold horn?

A: The horn is the extended portion of the threshold that runs under the door casing on each side. It prevents water from running behind the casing and provides a finished appearance.

Q: How do I know if my threshold needs replacement?

A: Signs that replacement is needed include visible rot, warping, gaps between the threshold and door, water stains, or difficulty opening and closing the door.

Q: Can a homeowner with basic skills complete this project?

A: Yes, threshold replacement is rated as moderate difficulty and is achievable for homeowners with basic DIY skills. The key is taking time to measure accurately and follow each step carefully.