Oak vs. Ash vs. Merbau: Which Timber Tread Is Best for Your Stairs?

Choosing the best timber supplier for stair treads is not simply about selecting the hardest or most attractive timber. For Australian homes and building projects, the right choice depends on where the stairs are located, expected traffic, exposure to moisture and weather, the appearance you want, the timber grade, tread dimensions, support conditions and the finish being applied.

In this guide to oak vs ash vs merbau stair treads, we compare three popular hardwood options and explain where each makes the most sense. European Oak and European Ash are primarily suited to protected interior applications, while Merbau is a particularly practical option when greater natural durability is required for exposed conditions.

Oak stair treads

Oak stair treads are a popular choice for contemporary and traditional interiors. European Oak combines a distinctive grain with good hardness, a warm appearance and considerable finishing flexibility.

European Oak typically ranges from pale yellow-brown to light brown, with a relatively open texture and characteristic grain. This makes oak timber stair treads suitable for projects where the staircase is intended to become a visible design feature rather than simply a functional element.

For homeowners and builders, one of the main advantages of Oak is its versatility. It can be left with a natural appearance or stained and finished to complement timber flooring, cabinetry and other interior elements.

Benefits of Oak Stair Treads

• Appearance: Oak has a recognisable grain pattern that adds character without overwhelming an interior.

• Hardness: European Oak is commonly reported at around 5.5–6.0 kN on the Janka hardness scale, providing good resistance to everyday indentation and wear.

• Interior suitability: European Oak is widely used for flooring, joinery and staircase applications.

• Finishing flexibility: Oak can be stained, polished or finished to achieve different visual effects.

• Design versatility: Its combination of colour and grain works across traditional, transitional and contemporary interiors.

Oak is therefore a strong contender when appearance, versatility and finishing options are priorities. It is particularly well suited to indoor hardwood stair treads where the timber is protected from prolonged exposure to weather.

Ash Stair Treads

Ash stair treads offer a lighter and more linear appearance than many Oak products. European Ash is generally pale in colour and has a pronounced, straight grain that can create a clean and contemporary staircase.

European Ash is also a hardwood with a Janka hardness commonly reported at around 6 kN, placing it in a similar general hardness range to European Oak.

For projects where a lighter staircase is preferred, ash timber stair treads can provide a distinctive natural appearance while retaining the character of real hardwood.

Benefits of Ash Stair Treads

• Appearance:-  Ash has a lighter base colour and prominent grain, making it suitable for bright and contemporary interiors.

• Hardness-: Its hardness is broadly comparable with European Oak, although actual performance varies according to grade and product specification.

• Interior suitability:- Ash is commonly used for flooring and interior timber applications.

• Finishing flexibility:- Its light colour provides flexibility when choosing clear or coloured finishes.

• Grain definition:- Its pronounced linear grain can create a clean architectural appearance.

The key consideration is application. Ash timber stair treads are primarily an internal option. Victorian Ash, for example, is described as having moderate above-ground durability and is best suited to interior applications including staircases.

If you are deciding between Oak or Ash for stairs, the choice will often come down to appearance, grain preference and the requirements of the project rather than a major difference in hardness.

Merbau Stair Treads

Merbau stair treads, also known as Kwila, occupy a different position in this comparison. Merbau is a dense tropical hardwood recognised for its natural durability and suitability for demanding external conditions.

Urban Treads lists Merbau as Durability Class 1 above ground and Class 3 for in-ground contact, with a seasoned density of approximately 830 kg/m³ and a Janka hardness of around 8.6 kN.

This combination of density, hardness and natural durability makes Merbau particularly relevant when timber stairs are exposed to outdoor conditions.

Benefits of Merbau Stair Treads

• Durability:- Merbau provides substantially higher natural durability for exposed applications than European Ash or European Oak.

• Hardness:- Its higher Janka rating provides good resistance to indentation and everyday mechanical wear.

• Appearance:- Freshly cut Merbau can range from yellowish or orange-brown through to deeper reddish-brown tones as it ages.

• Outdoor suitability:- Merbau is widely used where timber needs to withstand outdoor exposure.

• Versatility:- Depending on the product specification and installation, Merbau can be considered for both internal and external applications.

This makes Merbau external stair treads a logical option for decks, verandahs and other exposed stair applications where natural durability is important.

Merbau does have practical considerations. Its natural oils can affect finishing, and it may cause staining or bleeding around surrounding materials if it is not properly prepared and sealed. The final specification should therefore consider the timber, finish, fixing method and exposure conditions together.

Oak vs Ash vs Merbau: Key Differences

There is no universal winner in the Oak vs Ash vs Merbau comparison. Each species is suited to a different set of requirements.

Durability

Durability is one of the biggest differences between these three timbers.

European Oak and European Ash are generally better suited to protected interior applications. Merbau has significantly higher natural durability for above-ground exposure, making it better suited to external environments.

Hardness and Wear

Merbau has the highest Janka hardness of the three options discussed. Oak and Ash are broadly similar in hardness.

However, hardness should not be treated as a complete measure of stair performance. Tread thickness, span, support, timber grade, installation, moisture conditions and finish also influence how a staircase performs over time.

Appearance and Grain

Oak generally provides a warm and established hardwood appearance with distinctive grain character.

Ash is lighter and typically has a more pronounced linear grain, making it particularly suitable for contemporary interiors.

Merbau has a deeper and richer colour range, generally moving from yellowish or orange-brown tones towards deeper reddish-brown as the timber ages.

Indoor vs Outdoor Suitability

For protected internal stairs, both Oak and Ash can be suitable choices when the product specification meets the requirements of the project.

For exposed external stairs, Merbau generally has the strongest case of these three species because of its natural above-ground durability.

Maintenance

Maintenance requirements depend on the staircase environment, finish, exposure and traffic.

Interior Oak and Ash stairs generally require maintenance appropriate to the applied finish and level of household traffic. Exterior Merbau stairs are exposed to moisture, sunlight and changing weather conditions, so the finish and maintenance regime need to be selected accordingly.

Cost

There is no reliable rule that one of these species will always be the cheapest option. Stair tread pricing can vary according to timber species, grade, dimensions, thickness, finish, manufacturing requirements and supplier.

For a meaningful price comparison, compare like-for-like tread specifications rather than comparing species alone.

Moisture and Dimensional Movement

All timber responds to changes in moisture content. Timber can gain or lose moisture as environmental conditions change, which can cause dimensional movement.

For internal stair projects, appropriate acclimatisation and installation conditions should be considered, particularly where the building environment differs significantly from the timber's supplied moisture content.

For external stairs, the exposure conditions, drainage, detailing, fixing method, finish and natural durability of the timber all need to be considered.

Which Timber Is Best for Indoor Stairs?

For the best timber for indoor stairs, European Oak and European Ash are both strong choices when their appearance and product specifications suit the project.

Choose Oak if you want:

• A warm and established timber appearance.

• Distinctive grain character.

• A versatile base for staining and finishing.

• A staircase that complements traditional or contemporary interiors.

• A natural hardwood appearance that works well with other interior timber elements.

Choose Ash if you want:

• A lighter overall appearance.

• Strong, linear grain definition.

• A clean and contemporary aesthetic.

• A hardwood suitable for protected interior applications.

• A brighter alternative to the warmer tones commonly associated with Oak.

The better choice for indoor hardwood stair treads is therefore often aesthetic rather than simply structural. Both can produce excellent internal timber stair treads when correctly graded, manufactured, installed and finished.

One factor that should not be overlooked is moisture movement. Timber responds to changes in humidity by gaining or losing moisture, which can cause dimensional movement. Appropriate acclimatisation should therefore be considered before fabrication and installation where building conditions differ significantly from the timber's supplied moisture content.

Which Timber Is Best for Outdoor Stairs?

For the best timber for outdoor stairs, Merbau generally has the strongest case of these three species because of its natural durability.

Outdoor stairs face conditions that internal stairs do not, including rain, humidity, sunlight and repeated changes in moisture content. Selecting timber with appropriate natural durability is therefore critical.

Merbau is rated Class 1 for above-ground exposure in Urban Treads technical data. This makes it a strong candidate for Merbau outdoor stair treads and other external applications where exposure conditions are demanding.

However, "outdoor" does not automatically mean that every Merbau tread is suitable for every installation.

The actual product grade, dimensions, tread thickness, support, fixing method, drainage, finish and exposure conditions all matter. For an exposed staircase, check the complete tread specification rather than selecting timber species alone.

How Should You Choose Between Oak, Ash and Merbau?

Use this decision framework when comparing timber species for stair treads:

1. Start with location - Internal stairs can accommodate a broader range of timber species. External stairs require greater attention to natural durability and exposure.

2. Consider appearance -  Oak generally gives a warmer hardwood look, while Ash provides a lighter and more linear appearance. Merbau offers deeper brown and reddish tones.

3. Consider traffic -  Higher hardness can help resist indentation, but tread construction, timber grade and finish remain important.

4. Check the specification -  Confirm timber grade, tread thickness, dimensions and support requirements before ordering.

5. Consider moisture exposure -  Internal and external stairs have different moisture requirements and environmental risks.

6. Choose the finish carefully -  The coating must be appropriate for the timber and the environment in which the staircase will be used.

7. Plan for maintenance -  Interior and exterior timber stairs have different maintenance requirements, particularly where moisture and sunlight are involved.

8. Compare like-for-like pricing -  Consider grade, dimensions, thickness, finish and manufacturing requirements when comparing costs.

Remember that stair safety is not determined by timber species alone. Stair geometry, structural design, fixing, tread dimensions and slip resistance also need to be considered.

Urban Treads specifically identifies regulatory requirements, strength, durability and stair geometry as important design considerations.

Conclusion: Which Timber Tread Is Best?

The answer to Oak vs Ash vs Merbau stair treads depends on the application.

For indoor stairs, European Oak is an excellent all-round choice if you want warmth, grain character and finishing flexibility. European Ash is a strong alternative if you prefer a lighter appearance and prominent linear grain.

For outdoor stairs, Merbau is generally the more suitable choice because of its significantly higher natural durability and hardness for exposed applications.

Ultimately, the best hardwood for stairs is not necessarily the hardest species. It is the timber whose durability, appearance, grade, dimensions, finish and intended environment match the staircase.

If you are still comparing your options, our guide to where to buy premium hardwood stair treads in Australia explains what to look for in a specialist supplier, including timber selection, dimensions and product quality.

Before ordering timber treads, discuss the application, span, support conditions and finishing requirements with your staircase professional or timber supplier. Urban Treads can help you assess the available tread options and choose a specification suited to your project.

FAQs

Is Oak or Ash better for stair treads?

Both can be suitable for internal stair treads. Oak generally offers a warmer and more characterful appearance, while Ash tends to provide a lighter look with pronounced linear grain.

The better choice depends primarily on your preferred appearance, product specification and interior design.

Is Merbau better than Oak for outdoor stairs?

For exposed outdoor applications, Merbau generally has the advantage because its natural above-ground durability is substantially higher than European Oak.

Merbau is rated Class 1 above ground in Urban Treads technical data.

What is the most durable timber for stairs?

Of these three options, Merbau has the highest natural durability for above-ground exposure and the highest Janka hardness.

However, durability should always be assessed against the actual installation environment and product specification rather than the species name alone.

Are Oak stair treads suitable for Australian homes?

Yes. European Oak is widely used in Australian interior flooring and staircase applications. It is particularly suitable where the stairs are protected from weather and the desired result is a warm, natural timber appearance.

Are Ash stair treads suitable for outdoor stairs?

Ash is primarily suited to protected interior applications in the context discussed in this guide. For exposed outdoor stairs, Merbau generally offers a more suitable combination of natural durability and hardness.

Are Merbau stair treads suitable for indoor stairs?

Merbau can be used in different applications depending on the specific product and project requirements. Its high hardness and rich colour can make it an option for interior applications, although European Oak and European Ash are more directly positioned for protected interior applications in this comparison.

Which is harder, Oak, Ash or Merbau?

Based on the Janka hardness figures used in this guide, Merbau is the hardest of the three at approximately 8.6 kN. European Ash is around 6 kN, while European Oak is commonly reported around 5.5–6.0 kN.

Hardness is useful for comparing resistance to indentation, but it should not be treated as a complete measure of structural stair performance.

What should I consider when choosing timber stair treads?

Consider the stair location, exposure to moisture, timber species, grade, tread thickness, span, support, finish, expected traffic and maintenance requirements.

Correct design and installation are just as important as choosing the timber species.