How to Replace a Worn Door Threshold Strip Yourself

Replacing a worn door threshold strip is a satisfying weekend DIY job that most homeowners can handle with basic tools and a trip to the hardware store. A damaged or missing threshold strip lets in draughts, moisture, and insects — all significant concerns in New Zealand's varied climate — so it's worth sorting promptly. Here's how to do it properly.

What Is a Door Threshold Strip?

A door threshold strip (sometimes called a door bar or threshold seal) is the strip of material fitted at the base of a doorway, bridging the gap between two floor surfaces or sealing the bottom of an exterior door. They come in several types:

• Flat/cover strips – join two floor coverings of similar height (e.g., carpet to timber)
• Ramp/transition strips – bridge surfaces of different heights
• Draught-seal thresholds – exterior doors; include a rubber or brush seal that presses against the door bottom
• Aluminium threshold plates – common on external doors for weather resistance

For exterior doors, a good threshold seal is part of your home's weathertightness — something the NZ Building Code clause E2 (External Moisture) takes seriously.

Tools and Materials You'll Need

• Tape measure and pencil
• Hacksaw or mitre saw (for cutting metal strips)
• Flat pry bar or stiff putty knife
• Drill and appropriate drill bits
• Screwdriver (usually Phillips or flat)
• Safety glasses and work gloves
• New threshold strip (matched to your door width and floor type)
• Appropriate fixings (often supplied with the strip)
• Silicone sealant for exterior applications (a product like Sika Silicone or similar)

Step 1 – Measure Up and Choose the Right Strip

Measure the width of your doorway carefully — measure twice, cut once. Note the height difference between the two floor surfaces and whether the door is internal or external. Take photos of the existing strip and your floor types to the hardware store. Bunnings and Mitre 10 both stock a good range of threshold strips in aluminium, brass, and timber finishes.

Step 2 – Remove the Old Threshold Strip

1. Check whether the strip is screwed, nailed, or glued in place.
2. Remove any visible screws first.
3. Use a flat pry bar or stiff putty knife to gently lever the strip up, working along its length. Take care not to gouge the floor covering.
4. If it's glued, score along the edges with a utility knife before prying to avoid tearing vinyl or carpet.
5. Once removed, clean up any old adhesive, sealant, or debris from the subfloor. A scraper and some mineral spirits usually do the trick.

Step 3 – Prepare the Area

• Check the subfloor or door sill for any rot, swelling, or damage. Exterior sills showing rot should be assessed by a qualified tradesperson before you proceed — hidden moisture damage can be a sign of a larger weathertightness issue.
• If the existing screw holes are stripped, fill them with a timber plug or two-part epoxy filler and allow to cure before re-drilling.
• For exterior thresholds, run a bead of silicone sealant along the sill before fitting the new strip to create a weathertight seal.

Step 4 – Cut and Fit the New Strip

1. Mark your cut line on the new strip using your measurements.
2. Cut aluminium strips with a hacksaw or fine-tooth saw blade; use a mitre saw for timber strips. Always wear safety glasses when cutting metal.
3. Offer the strip up to check the fit before fixing — it should sit snugly between door architraves without forcing.
4. For screw-fixed strips: pre-drill pilot holes to avoid splitting or cracking, then fix with the supplied screws. Don't overtighten — you want the strip snug, not bowed.
5. For adhesive-fixed strips (common on internal carpet-to-hard-floor transitions): apply the recommended adhesive or double-sided tape, press firmly, and allow the recommended cure time before foot traffic.

Step 5 – Check the Door Clearance

Once the new strip is fitted, open and close the door several times. The door should swing freely without dragging on the strip. If it catches, you may need to:

• Adjust the strip position slightly
• Plane a small amount off the door bottom (this is straightforward for timber doors)
• Check whether the door hinges need adjustment

For exterior draught-seal thresholds, the rubber or brush seal should make light, even contact with the door bottom when closed. This is important for meeting Healthy Homes draught-stopping requirements if you're a landlord.

Choosing the Right Sealant for Exterior Thresholds

For any exterior application, use a UV-stable, paintable silicone or polyurethane sealant rated for exterior use. Products from Sika are widely available and trusted in the NZ trade. Avoid standard white bathroom silicone outdoors — it degrades quickly in sunlight.

When to Call a Professional

This is generally a safe DIY job, but call a qualified handyman or tradesperson if:

• You find rot, soft timber, or moisture damage in the door sill or surrounding framing — this may indicate a weathertightness issue requiring proper assessment
• The door frame itself is damaged or out of square
• You need to trim the bottom of a fire door — fire doors are a restricted building element and must not be modified without checking manufacturer specifications
• You're unsure about building consent — most like-for-like threshold replacements are exempt under Schedule 1 of the Building Act, but always confirm with your local council if in doubt
• The job involves structural sill replacement, which may require a Licensed Building Practitioner (LBP)

A skilled local handyman can complete a threshold replacement quickly and correctly. You can find qualified tradespeople in your area at tradedirectory.co.nz.

Sources & Further Reading

• MBIE Building Performance – NZ Building Code
• Tenancy Services – Healthy Homes Standards
• Sika NZ – Sealants and Adhesives
• Bunnings NZ – Door Threshold Strips
• Mitre 10 NZ – Door Hardware
• Licensed Building Practitioners