Best Modified Wood for Decking, Cladding, and Siding (2026): Accoya vs Kebony vs Lunawood

Patio Lunawood deck with chairs
Title

In the quest for eco-friendly and long-lasting building materials, modified wood has changed the game. Three brands (all available in Ontario) that come up the most in decking, cladding, and siding conversations are Accoya, Kebony, and Lunawood ThermoWood.

 

This isn’t about picking a single “winner”. It’s about choosing the material that best matches your climate, design goals, and maintenance expectations.

Quick takeaways

  • Want the longest durability warranty and outstanding dimensional stability? Accoya is hard to beat (50 years above ground).
  • Want hardwood-like hardness and a dark-brown look that naturally silvers? Kebony is a top pick (Janka 1618 lb; 30-year rot warranty for many products).
  • Want a chemical-free thermal modification process and a proven ~30-year expected service life for cladding/decking applications? Lunawood ThermoWood is a favourite (Durability class 2; Use class 3; 30-year expected service life via BRE endorsement).

At Composite Deck Shop, we’re here to help you make an informed decision for your next project.

by Alex Krupin (LinkedIn profile)

Founder and Director of Composite Deck Shop

What is modified wood?

Modified wood is still real wood — it’s simply treated to improve durability and stability.

The three most common modification methods in this comparison:

1) Lunawood ThermoWood – Thermally modified wood

Lunawood is made using heat and steam (ThermoWood process) and is suitable for Use class 3 applications (above ground, exposed to weather), and not recommended for direct ground contact.

2) Kebony – Furfurylated wood

Kebony uses a bio-based modification process (furfurylation). Their product documentation emphasises high resistance to decay/fungi/insects and supports long rot-warranty terms (varies by product line and residential vs commercial use).

3) Accoya – Acetylated wood

Accoya is produced by acetylation, a process that modifies the wood from surface to core to improve durability and dimensional stability. Accoya’s technical guide lists Durability Class 1 (EN durability classification) and provides a 50-year above-ground / 25-year in-ground or freshwater durability guarantee (when used and installed per guidance).

Modified wood comparison (Durability, stability, and “what it feels like underfoot”)

Here’s a comparison you can actually use when deciding:

Brand

Modification

Durability / use class

Warranty / service life

Hardness (Janka)

Lunawood ThermoWood

Heat + steam

Use class 3; Durability class 2

Expected service life ~30 years (BRE endorsement)

Spruce/Pine ~1700 N (382 lbf); harder species available in some collections

Kebony

Furfurylation

Designed for high decay resistance

30-year rot/decay warranty (varies by product & use type)

1618 lb (7.2 kN)

Accoya

Acetylation

Durability Class 1; highly stable

50 yrs above ground / 25 yrs in-ground or freshwater (per warranty terms)

4,100 N side / 6,600 N end (ASTM D143)

Important note: “Warranty” and “expected service life” are not the same thing.

  • Accoya and Kebony publish clear warranty terms and durations (with conditions).
  • Lunawood publishes use class/durability class and a BRE-endorsed expected service life for cladding/decking (and also publishes separate warranty info for certain applications/regions).

Visual appeal & maintenance (what happens after 6–12 months outside)

All three products can look stunning on day one — and all three will weather if left unfinished.

Accoya (look + upkeep)

  • Natural colour: light/blonde tone.
  • Will naturally weather/silver outdoors if uncoated.
  • If you’re coating/finishing, end-grain sealing is a key best practice for long-term coating performance.

Kebony (look + upkeep)

  • Natural colour: rich brown tone that fades to a silver-grey patina when left unfinished.
  • For several decking products, Kebony states no finishing is required to maintain warranty.
  • Kebony also notes (for certain deck boards) that end-seal wax is not needed or recommended.

Lunawood (look + upkeep)

  • Natural colour: warm golden-brown tone.
  • Lunawood notes the greying process can become visible quickly (3–6 months) depending on UV exposure and conditions.
  • If you want to maintain the original appearance, Lunawood recommends applying an oil or approved coating, and they give specific coating guidance (including what not to use).
    • Example: Lunawood explicitly says linseed oil is not suitable for ThermoWood because it can enable fungal growth.

Installation best practices (this matters more than people think)

A lot of “material problems” are actually installation detail problems — especially on decks in wet/shaded zones.

Lunawood best practices (vendor guidance)

  • Use stainless steel fastenings.
  • Ensure sufficient ventilation around the boards.
  • Joist spacing guidance: for 26 mm decking, max 450 mm centres; for 40 mm decking, 600 mm centres.
  • Pre-drill when mounting is less than 70 mm from the end of a profile to reduce cracking risk.
  • Lunawood is not recommended for direct ground contact (Use class 3).

Accoya best practices (vendor guidance)

  • Accoya publishes durability and performance data and stresses correct design/installation; their technical guide also includes saltwater notes (OK around saltwater, but not warranted for marine borers in permanent immersion).
  • For coated systems, Accoya’s coatings guidance is clear: seal all end grain with a compatible sealer.

Kebony best practices (vendor guidance)

  • Kebony documentation highlights weathering as normal and not affecting durability; they also provide product-level instructions/claims like “no finishing required to maintain warranty” for certain decking lines.

Cost in 2026 (the honest answer)

Modified wood pricing changes a lot based on:

  • profile/thickness/grade,
  • availability and lead times,
  • exchange rates and shipping.

Best practice: treat any “$ per linear foot” you see online as a ballpark, then request a project quote based on your exact profile, square footage, and fastening method.

Price note (2024 historycal snapshot)

Modified wood pricing changes with profile, thickness, length, grade, and supply. To keep this section useful, we’re showing (1) a brief historical 2024 snapshot as $/lnft (per linear foot) for context, and (2) live pricing for Lunawood via the product cards below.

• Accoya: $7–$9
• Kebony: $9-12
• Lunawood: $3.60-4.50

Available Modified Wood We Carry: Lunawood ThermoWood

At Composite Deck Shop (Ontario and Quebec), we carry Lunawood ThermoWood because it’s thermally modified using only heat and steam (no added chemicals) and is designed for a wide range of uses, including decking, exterior cladding, and interior panelling. 

 

Below are our most popular Lunawood profiles with current “starting from” pricing per linear foot—availability can change quickly, so we recommend confirming stock for your exact profile and quantity:

Sustainability & certifications (what’s actually documented)

Accoya

  • Accoya publishes its 50/25 durability warranty (above ground / in-ground or freshwater).
  • Accoya has been re-awarded Cradle to Cradle Certified® Gold (including material health noted in their announcement).

Kebony

  • Kebony publishes rot/decay warranty language and product documentation; product datasheets show certifications and durability-related specs.

Lunawood

  • Lunawood’s raw materials come from well-managed Nordic forests; they state that in Finland only 75% of annual growth is cut, and four seedlings are planted for each tree cut.
  • Lunawood highlights certifications including PEFC/FSC and Nordic Swan Ecolabel.

Modified wood vs composite/PVC (when to pick what)

If you love real wood feel and you’re OK with natural patina (or periodic oiling), modified wood is a great option. If you want:

  • more consistent colour,
  • less surface maintenance,
  • and predictable long-term appearance, then premium capped composite or PVC can be a better match — especially in shaded/wet backyards.

(Composite Deck Shop carries major composite/PVC lines like AZEK/TimberTech, Trex, Fiberon, and Eva-Last.)

Need help choosing the right material for your backyard?

We can help you compare these options based on your site conditions (shade, trees, moisture, salt exposure, traffic) and your desired look (natural patina vs “stay closer to original colour”).

 

Visit our showrooms in Vaughan, Peterborough, London, or Barrie or call (888) 788-6788.

Have questions?
We have answers!

Q1: What is modified wood?

A: Modified wood is real wood that has been treated to improve durability and stability. Common methods include acetylation (Accoya), furfurylation (Kebony), and thermal modification with heat and steam (Lunawood ThermoWood).

Q2: How long does modified wood last outdoors?

A: It depends on the product and exposure. Accoya publishes a 50-year above-ground durability warranty, Kebony publishes warranty terms up to 30 years for many products, and Lunawood publishes durability/use class guidance plus a BRE-endorsed ~30-year expected service life for cladding/decking applications.

Q3: Which modified wood is the most dimensionally stable?

A: Accoya is known for exceptional stability; their technical guide shows very low shrinkage and documents durability class performance. Lunawood also highlights dimensional stability due to lowered equilibrium moisture content.

Q4: Which modified wood is the hardest (best for heavy traffic decks)?

A: Hardness depends on the specific product/species. Accoya publishes Janka values, Kebony deck board datasheets publish Janka hardness (e.g., 1618 lb for Kebony Clear deck board #2522), and Lunawood’s technical datasheet shows different Janka values by species/collection.

Q5: Do Accoya, Kebony, and Lunawood turn grey over time?

A: Yes. Like most exterior woods, they weather in UV and will develop a silver-grey patina if left unfinished. Lunawood notes greying can be visible within 3–6 months depending on exposure.

Q6: Do I need to oil or stain modified wood?

A: Not for durability in many cases — but if you want to preserve the original colour, a UV-protective oil/coating is typically recommended. Lunawood provides specific coating guidance and notes linseed oil is not suitable for ThermoWood.

Q7: Can modified wood be installed in direct ground contact?

A: Thermally modified Lunawood (Use class 3) is not recommended for direct ground contact. Always follow the manufacturer’s use class guidance for your exact product.

Q8: What fasteners should I use for modified wood decking?

A: As a best practice, use corrosion-resistant fasteners. Lunawood specifically states to use stainless steel fastenings and to ensure sufficient ventilation.

Q9: Modified wood vs composite/PVC — which is lower maintenance?

A: Composite/PVC typically wins on “set it and forget it” appearance and consistent colour. Modified wood offers a premium real-wood feel and can be low-maintenance structurally, but it naturally weathers unless you maintain the surface finish.

In this blog

What is modified wood?

Modified wood comparison

Appearance & Maintenance

Installation Tips

2026 Cost

Sustainability

Modified wood vs composite/PVC

FAQ