A broken stair tread is more than just an eyesore, it’s a serious safety hazard. Fortunately, repairing a cracked or damaged tread is a relatively straightforward DIY project. In the video above, This Old House general contractor Tom Silva reveals his quick and effective method for repairing a cracked wooden stair tread to get your stairs back in shape.
Assessing the Stair Tread Damage
Before beginning the repair process, it’s important to evaluate the extent of the damage to determine the best course of action.
Determining If Repair Is Possible
In many cases, you can fix a cracked or split tread without replacing the entire board. But if the damage is severe or there’s wood rot, replacement might be necessary. Carefully inspect the tread for any signs of extensive decay or structural weakness.
When To Replace Instead of Repair
We recommend replacing the tread if:
- The wood is soft, spongy, or shows signs of rot
- Multiple large cracks or splits are present
- The tread shows signs of warping or is no longer level
- Previous repairs have failed
Gathering Tools and Materials to Repair Stair Treads
To repair a broken stair tread, you’ll need the following tools and materials ready before you begin:
- Drill/driver
- Tapered drill bit
- Carpenter’s glue
- Glue syringe
- Hammer
- Hand file
- Layout square
- Tapered wooden dowels (matching the wood species of your stairs)
- Clean cloth
Step-by-Step Repair Process for a Broken Wooden Stair Tread
Follow these steps to fix your broken stair tread:
1. Drilling Holes for the Dowels
Start by drilling three holes into the edge of the cracked stair tread using a tapered drill bit. This bit should match the diameter of the wooden dowels you’ll be using. To create straight, level holes, Silva follows this process:
- Mark the center points for your holes along the edge of the tread.
- Use a layout square to align your drill perpendicular to the tread surface.
- Drill slowly and steadily, maintaining consistent pressure.
2. Applying Glue to the Crack
Once you’ve drilled the holes, it’s time to apply glue to the crack:
- Gently pull on the front edge of the tread to open the crack slightly.
- Use a glue syringe to inject the carpenter’s glue into the crack.
- Wiggle the tread to work the glue down into the crack. Be sure to confirm that you’ve gotten full coverage before moving on.
3. Inserting and Securing the Dowels
With the glue in place, you can now insert the dowels:
- Apply a generous amount of glue to each dowel.
- Insert the first dowel into one of the drilled holes.
- Use a hammer to tap the dowel firmly into place.
- Repeat this process for the remaining two dowels.
4. Cleaning Up Excess Glue
After inserting all the dowels, use a clean, damp cloth to wipe away any excess glue that has squeezed out. Be thorough—you want to create a clean finish once the glue dries.
5. Filing Down the Dowels
The final step is to file the dowels flush with the tread surface:
- Allow the glue to dry completely according to the manufacturer’s instructions.
- Use a hand file to carefully file down the ends of the dowels.
- Work slowly and check your progress frequently to avoid over-filing.
Additional Tips for a Strong Repair
To make sure your repair is strong, follow our best practices:
- Select dowels that match the wood species of your stairs.
- Lightly sand the repaired area after filing to smooth any rough spots and blend the repair.
- Apply wood filler or putty to cover small gaps or imperfections, then sand again.
- If you plan to refinish the stairs, do so after the repair for an even finish.
When To Call a Professional
While repairing a broken stair tread is usually a manageable DIY project, there are times you might need professional help. We recommend calling a pro if:
- Multiple treads are damaged or unstable.
- The underlying structure of the stairs is compromised.
- You’re uncomfortable working with power tools or carpentry.
- The repair involves load-bearing elements of the staircase.
In these cases, consulting with a licensed carpenter or contractor is the best way to guarantee the safety and integrity of your stairs.
