How to Repair or Replace a Damaged Stair Tread

A damaged stair tread — whether it's cracked, rotted, squeaky, or just worn through — is more than an eyesore; it's a genuine safety hazard for your household. The good news is that many stair tread repairs are well within the reach of a confident DIYer with basic carpentry skills. More extensive work, or stairs that form part of a structural system, may need a licensed professional.

Assess the Damage First

Before reaching for your tools, take a good look at what you're dealing with. The type of repair depends heavily on the extent and cause of the damage.

• Surface wear or minor cracks — often repairable with filler, sanding, and refinishing.
• Squeaking treads — usually caused by movement between the tread and the stringer or riser; fixable without full replacement.
• Rot or structural damage — common in older NZ homes, especially in damp climates or where water has been getting in. Full tread replacement is usually needed.
• Broken or split tread — replacement is the safest option.

Also check the stringers (the side supports) and risers (the vertical boards between treads). If these are damaged too, the repair becomes more involved.

Tools and Materials You'll Need

• Pry bar and hammer
• Circular saw or hand saw
• Drill/driver and screws (structural screws, e.g. 75–100 mm)
• Tape measure and pencil
• Sandpaper or orbital sander
• Timber for replacement tread (see below)
• Construction adhesive (e.g. Sika or similar)
• Wood filler or epoxy filler for minor repairs
• Finish of your choice — paint, stain, or clear coat

Choosing the Right Timber

For interior stairs, common NZ choices include pine (radiata), rimu, kwila (merbau), or LVL (laminated veneer lumber). Match the species and thickness to your existing treads where possible — standard tread thickness is typically 32–42 mm for residential stairs.

For exterior stairs, always use a treated timber rated H3.2 or above to resist moisture and decay, in line with good building practice and the NZ Building Code. Check with your local timber merchant at Mitre 10, PlaceMakers, or Bunnings for what's available in your area.

Repairing a Squeaky Tread

Squeaks happen when timber rubs against timber. Here's how to fix it:

1. Locate the squeak by stepping slowly along the tread.
2. From above, drill pilot holes and drive 75 mm structural screws at an angle through the tread into the riser below (toe-screwing).
3. Alternatively, apply a bead of construction adhesive into the joint between the tread and riser, then weight it down overnight.
4. Fill screw holes with wood filler, sand flush, and refinish.

Replacing a Damaged Tread — Step by Step

1. Remove the Old Tread

Use a pry bar to carefully lift the tread. Work from the front edge, being careful not to damage the stringers. If the tread is glued and screwed, you may need to score along the edges with a utility knife first.

2. Clean Up the Surface

Remove any old adhesive, nails, or staples from the stringers. Check the stringers for rot or damage — if they're compromised, stop and consult a carpenter.

3. Cut the New Tread to Size

Measure the width (front to back, called the going) and length carefully. In NZ, the Building Code (specifically NZS 3604 for timber-framed buildings) sets minimum requirements for stair geometry — a going of at least 250 mm and a rise of no more than 220 mm for domestic stairs. Don't change the tread depth when replacing, as this can create an uneven stair that becomes a trip hazard.

4. Fit and Fix the New Tread

• Apply a bead of construction adhesive to the top of the riser and stringers.
• Set the new tread in place, ensuring it's flush and level.
• Secure with 75–100 mm structural screws through the tread into the riser and stringers. Pre-drill to avoid splitting.
• Countersink screws and fill holes.

5. Sand and Finish

Sand the new tread smooth, feathering into any adjacent surfaces. Apply your chosen finish — Resene and Dulux both offer durable floor and stair finishes suitable for high-traffic areas. For a natural timber look, a penetrating oil or polyurethane is popular.

Does This Work Need a Building Consent?

Like-for-like replacement of a single stair tread is generally considered maintenance and is typically exempt from building consent under Schedule 1 of the Building Act. However, if you're altering the stair geometry, replacing multiple treads, or the staircase is part of a structural system, you should check with your local council before starting. Rules can vary, so it's always worth a quick phone call. See MBIE Building Performance for general guidance.

When to Call a Professional

Some stair situations are best left to a qualified carpenter or Licensed Building Practitioner (LBP):

• Structural damage to stringers, newel posts, or balustrades
• Rot that has spread beyond the tread into the framing
• Exterior stairs with significant decay or instability
• Balustrade or handrail work — these have strict height and strength requirements under the Building Code and may require consent
• Any work where you're unsure about the structural integrity of the staircase

A good local carpenter can assess the full picture and ensure the repair is safe and compliant. You can find qualified tradespeople in your area on tradedirectory.co.nz.

Safety Note

Always secure the work area and warn household members that the stair is out of action. Never leave a stair tread partially removed overnight without a clear barrier in place. If the staircase is the only access to an upper floor, plan the work carefully.

Sources & Further Reading

• MBIE Building Performance — Building Code
• Licensed Building Practitioners (LBP)
• BRANZ — Building Research
• Resene — Floor & Stair Finishes
• Bunnings NZ — Timber & Fixings
• PlaceMakers — Timber Products