What Is Thermally Modified Ash?

Thermally modified ash is a hardwood that undergoes a specialized heat-treatment process. During thermal modification, the wood is heated to high temperatures in a controlled, oxygen-free environment without the use of chemicals.

This process changes the wood's cellular structure, making it more dimensionally stable and significantly more resistant to moisture, decay, and insects.

The result is a durable hardwood with improved outdoor performance while maintaining the natural beauty of ash.

Key Benefits

• Excellent dimensional stability
• Increased resistance to rot and insects
• Chemical-free modification process
• Sustainable and environmentally friendly
• Attractive rich brown color

What Is Ipe?

Ipe, often referred to as Brazilian Walnut, is an extremely dense tropical hardwood native to Central and South America.

It has earned a reputation as one of the most durable decking materials available because of its natural resistance to weather, insects, decay, and heavy wear.

Its exceptional hardness makes it suitable for demanding outdoor applications, although its density also makes installation more challenging.

Key Benefits

• Exceptional durability
• Naturally resistant to insects and decay
• Extremely hard surface
• Long service life
• Premium appearance

Appearance Comparison

Both woods offer beautiful natural aesthetics, but their appearance differs considerably. Thermally modified ash features warm golden-brown to chocolate-brown tones with a straight, consistent grain pattern. Over time, it develops an elegant silver-gray patina if left untreated.

Ipe has a darker appearance, ranging from olive-brown to deep reddish-brown. Its grain is tighter and more varied, giving it a luxurious, exotic look.

Durability and Weather Resistance

Durability is one of the biggest factors when selecting exterior wood. Ipe is naturally among the most durable hardwoods in the world. Its dense fibers provide excellent resistance to moisture, insects, fungi, and harsh weather conditions.

Thermally modified ash achieves impressive durability through its heat-treatment process. While it may not be as naturally dense as ipe, thermal modification greatly enhances its ability to withstand outdoor environments.

For residential decks, siding, pergolas, and cladding, thermally modified ash provides excellent long-term performance.

Dimensional Stability

One of the biggest advantages of thermally modified ash is its dimensional stability. Because the heat-treatment process reduces the wood's ability to absorb moisture, it experiences less expansion, contraction, warping, and twisting during seasonal weather changes.

Although ipe is highly durable, it can still experience some movement due to moisture because it has not undergone thermal modification.

Maintenance Requirements

Both materials require relatively low maintenance. Thermally modified ash can be cleaned periodically and optionally treated with UV-protective oil to preserve its original brown color. Without maintenance, it naturally develops a silver-gray finish.

Ipe also benefits from occasional oiling if maintaining its rich dark color is important. Otherwise, it too will weather into a gray patina over time.

Sustainability

Sustainability has become an increasingly important consideration for homeowners, architects, and builders.

Thermally modified ash is generally regarded as the more environmentally responsible choice because it uses responsibly harvested hardwood and improves durability without chemical preservatives.

Ipe can also be sustainably sourced when certified by responsible forestry organizations, but concerns over tropical hardwood harvesting make sourcing especially important.

Installation

Installation requirements vary considerably. Thermally modified ash is easier to cut, drill, and fasten using standard woodworking tools.

Due to its exceptional hardness and density, ipe usually requires pre-drilling and specialized fasteners, increasing both labor time and installation costs.

Cost Comparison

Thermally modified ash generally offers a more affordable solution while still providing premium outdoor performance.

Ipe is typically more expensive because of its density, imported origin, and higher installation costs. Although the upfront investment is greater, many homeowners choose ipe for its extremely long lifespan.

Best Applications

Which Wood Should You Choose?

Choose thermally modified ash if you want a sustainable, dimensionally stable, attractive hardwood that offers excellent outdoor performance with easier installation and a more budget-friendly price.

Choose ipe if your priority is maximum durability, extreme hardness, and a premium tropical appearance, and you are comfortable with the higher material and installation costs.

Both woods are excellent choices for outdoor applications, and the right option ultimately depends on your project's budget, environmental priorities, design preferences, and performance requirements.