Installing a door bar (also called a transition strip or threshold bar) between two floors at different heights is a manageable DIY project for most homeowners. The key is choosing the correct type of bar for your height difference and floor materials, then fitting it securely so it lies flat, looks tidy, and won't become a trip hazard.
Why the Right Transition Strip Matters
When two floors meet at a doorway — say, timber floating floor in the lounge and ceramic tiles in the hallway — there's often a height difference of anywhere from a few millimetres up to around 15–20 mm. Without a proper transition strip, you're left with an exposed edge that can chip, crack, or become a genuine trip hazard. Under the NZ Building Code, internal floor level changes can also have accessibility implications, so it's worth getting the finish right.
Types of Door Bar / Transition Strip
Choosing the correct profile is the most important decision:
| Strip Type | Best For | Height Difference |
|---|---|---|
| Flat/Overlap bar | Same or very similar heights | 0–3 mm |
| Reducer/Ramp bar | One floor higher than the other | 5–15 mm |
| T-bar | Same height, gap between floors | 0–3 mm |
| End/Carpet bar | Carpet meeting hard floor | 0–10 mm |
| Stair nosing | Step-down between rooms | 15 mm+ |
For most situations where one floor is noticeably higher than the other, a reducer bar (sometimes called a ramp or slope bar) is what you need. These are widely available at Bunnings and Mitre 10 in aluminium, stainless steel, and timber-look laminate finishes.
Tools and Materials You'll Need
- Tape measure and pencil
- Hacksaw or angle grinder with metal-cutting disc (for aluminium bars)
- Drill and appropriate drill bits
- Hammer or rubber mallet
- Screwdriver
- Safety glasses and gloves
- The transition strip kit (bar + track/channel if required)
- Appropriate fixings (screws and plugs for concrete, or nails/screws for timber subfloor)
Step-by-Step Installation
1. Measure the Doorway
Measure the width of the doorway opening at floor level. Most standard NZ interior doorways are 810–910 mm wide. Cut your transition strip to length using a hacksaw — always cut from the decorative face side upward (or check the manufacturer's guidance for your specific bar material) to avoid chipping.
2. Identify Your Subfloor Type
Know whether you're working over a concrete slab or a timber subfloor — this determines your fixing method.
- Concrete slab: You'll need to drill and plug the floor, then screw the track down. Use a hammer drill with a masonry bit sized to match your wall plugs.
- Timber subfloor: You can screw or nail directly through the track into the timber.
3. Position the Track or Channel
Most reducer bars come with a separate aluminium track that screws to the floor first. Position the track so it sits centred under the door stop (the door's closed position). Mark your fixing holes with a pencil.
4. Drill and Fix the Track
Drill your holes, insert plugs if needed, and screw the track firmly to the subfloor. Check it's sitting flat and won't rock. On a concrete slab, ensure you're not drilling into any in-slab services — if you're unsure about underfloor heating cables or pipes, check your building plans or consult a professional.
5. Snap or Screw the Bar into the Track
Slide or snap the decorative bar into the track according to the manufacturer's instructions. Most modern bars click into place; some require screwing from above. Give it a firm press along the full length to ensure it's seated evenly.
6. Check for Trip Hazards
Run your hand along the bar — there should be no sharp edges or lips that could catch a foot. The ramp should slope gradually from the higher floor down to the lower one. If the bar is rocking or not sitting flush, remove it and re-check the track fixing.
Dealing with Large Height Differences
If the height difference is greater than about 15–20 mm, a standard reducer bar may not be sufficient. In this situation, you may need to:
- Build up the lower floor with a self-levelling compound (products from Ardex or Mapei are well regarded in NZ) before laying the flooring, reducing the step before you install the bar.
- Use a stair nosing profile if the drop is effectively a step.
- Consult a flooring installer for advice on the best approach.
For accessible design — particularly important in rental properties under the Healthy Homes Standards or in homes where mobility is a consideration — minimising floor level changes is always preferable.
Matching Your Finish
Transition strips come in a wide range of finishes. Aluminium bars can be left natural or painted. Timber-look laminate bars are popular for matching floating floors. Take a photo of your floor or bring a sample to Bunnings, Mitre 10, or PlaceMakers to find the closest match.
When to Call a Professional
This is generally a safe DIY task, but consider calling a qualified flooring installer (you can find local professionals on tradedirectory.co.nz) if:
- The height difference is large and you're unsure how to build up the subfloor correctly.
- You're working around underfloor heating — drilling into heating cables or pipes is a serious and costly mistake.
- The existing floors are damaged or uneven and need remediation before a bar can be fitted.
- You're working in a rental property and need to meet Healthy Homes compliance — a professional can confirm the installation is up to standard.
For any electrical underfloor heating work, always use a registered electrician — this is restricted electrical work under the Electrical Workers Registration Board (EWRB) rules and must not be done by an unlicensed person.
