Merbau Wooden Windows - Janka 7620 N, Class 1-2

Merbau Wooden windows – Janka 7620 N, Durability Class 1‑2

Merbau (Intsia bijuga / palembanica) from South‑East Asia delivers 815 kg/m³ density, 7,620 N Janka hardness, and Class 1‑2 natural durability – one of the densest and hardest tropical species in our range. Its high density and hardness make it a mechanically demanding choice, with a thermal penalty: λ ~0.19 W/m·K. Not in stock; made to order with extended lead times.

Request a Free Quote View technical specifications
lemn Merbau
  • Profil stratificat Merbau
  • Profil + textura + structura Merbau
  • Structura microscopica Merbau
  • Textura lemnului Merbau

Density 815 kg/m³

Heaviest in range

Janka 7,620 N

4.5× harder than spruce

Durability Class 1‑2

Maximum rot resistance

One of the Densest and Hardest Tropical Species in our Range

At 815 kg/m³ and 7,620 N Janka, merbau surpasses every other species in our collection on density and hardness. Class 1-2 natural durability places it among the most resistant woods available for exterior joinery. Its signature orange-brown colour, interlocked grain and exceptional rigidity (MOE 15.93 GPa) make it the tropical choice where no compromise on mechanical performance is acceptable. A thermal conductivity of ~0.19 W/m·K demands careful PHPP consideration.

Merbau wood texture

Technical Data – Merbau

Property

Value

Density

815 kg/m³

Janka Hardness

7,620 N

Bending Strength

145.2 MPa

Modulus of Elasticity

15.93 GPa

Compressive Strength

73.4 MPa

Radial Shrinkage

2.9 %

Tangential Shrinkage

4.8 %

Volumetric Shrinkage

8.2 %

Thermal Conductivity (λ)

~0.19 W/m·K

Natural Durability Class

1‑2 (very durable)

What these figures mean for joinery: A Merbau sash weighs nearly double a spruce sash of the same size – hardware must be sized accordingly. MOE 15.93 GPa provides the highest profile rigidity in our range. Radial shrinkage of 2.9% is exceptionally low for such a heavy wood, giving Merbau excellent dimensional stability. The thermal conductivity of ~0.19 W/m·K is among the highest in the compared range and must be accounted for in PHPP calculations.

Performance in Windows

Merbau provides unmatched hardness and durability, albeit with a thermal conductivity among the highest in our range.

1

Thermal

λ ~0.19 W/m·K – among the highest values in the compared range. For nZEB projects with Uw ≤1.0 W/m²K, Merbau on IV92 or D92 can reach the limit, but softwoods are thermally more efficient. Exact Uf/Uw values are calculated on request.

2

Hardness

7,620 N Janka – 4.5× harder than spruce, 1.5× harder than oak. Thresholds, sills, and high‑traffic entrance doors in Merbau remain unmarked even after decades of daily use.

3

Durability

Class 1-2 natural durability – extremely resistant to rot, moderately resistant to termites and good against marine borers. Untreated merbau lasts decades outdoors. In the Romanian climate, with correctly applied industrial finishing, long-term performance depends on the finish and maintenance.

Long‑term Performance

Merbau’s natural durability and outstanding dimensional stability deliver decades of reliable service, with one specific maintenance consideration.

Natural Durability

Dimensional Stability

Radial shrinkage 2.9% – among the lowest in the range for such a dense wood. Tangential 4.8% is better than spruce or oak. Merbau profiles stay straight and tight even with seasonal humidity swings.

Tannin Note

Merbau releases red‑brown tannin when wet, which can stain concrete, stone, or ceramics. Proper drainage details and joint sealing during installation minimise this, but clients must be informed.

Processing note: merbau’s extreme hardness and interlocked grain accelerate CNC tool wear. This higher machining cost is reflected in the final price.

Advantages of Merbau

Advantages

  • Janka 7,620 N – second hardest in our range, after Afzelia (8,230 N)
  • Class 1‑2 natural durability – full resistance to rot, termites, and marine borers
  • MOE 15.93 GPa – the most rigid profile in our range; minimal deflection under load
  • Outstanding dimensional stability – radial shrinkage 2.9%, tangential 4.8%
  • Warm orange‑brown tone with natural lustre – a distinctive tropical aesthetic

Disadvantages

  • λ ~0.19 W/m·K – among the highest in the compared range; penalises the final Uw
  • Weight 815 kg/m³ – hardware must be verified for large sashes
  • Active tannin – red‑brown stains on adjacent stone/concrete when wet
  • IUCN Vulnerable – FSC mandatory for responsible sourcing
  • Higher cost and longer lead time compared to European species
Request a Quote for Merbau Joinery

Comparison with Other Essences

How Merbau measures against the most relevant alternatives in our tropical and hardwood range.

Merbau vs Oak

Merbau wins on hardness (7,620 vs 4,980 N), durability (Class 1‑2 vs 2), and termite resistance. Oak wins on thermal (λ 0.18 vs 0.19 – small margin), cost, and in‑stock availability. For extreme‑traffic doors, Merbau justifies the premium.

Merbau vs Afzelia

Afzelia (835 kg/m³, 8,230 N) is slightly denser and harder, with pure Class 1 durability and acid resistance. Merbau (Class 1‑2) has a warmer orange‑brown appearance. Both are special‑order tropical species; availability often drives the decision.

Merbau vs Accoya

Accoya (λ ~0.11) is thermally far superior. Merbau wins on raw hardness (7,620 vs 4,100 N). For nZEB projects with difficult exposure, Accoya is the thermally smart choice; for maximum hardness on traffic surfaces, Merbau leads.

Appearance and Colour

Freshly cut Merbau displays a vivid orange‑brown hue that matures to a deep reddish‑brown. Yellow mineral flecks are a natural signature of the species. Under translucent stains the colour is warm, tropical, and highly varied between pieces. With opaque RAL paint the appearance is uniform with any other wood.

Availability & SM WOOD Execution

Key Details

  • Made to order – not in stock. Lead times confirmed at quoting due to variable supply from South‑East Asia.
  • Available on IV92, D92 and wood‑aluminium series.
  • FSC certification mandatory – Intsia bijuga is IUCN Vulnerable. Discussed at quoting.
  • Premium pricing; hardware verification for sash weight included at quotation stage.
Contact us for Merbau availability

Price depends on profile, dimensions, and hardware – request a free quotation. For B2B projects we supply complete PHPP data (Uf, Uw, Ug, g‑value, psi‑spacer) upon request.

When Merbau is the Right Choice – and When It Isn’t

Merbau is the right choice when:

  • The main entrance door undergoes extreme daily traffic and must remain unmarked for decades.
  • Class 1‑2 natural durability is a documented requirement for a difficult exposure (marine zone, tropical climate, southern face without roof).
  • Adjacent surfaces are dark or the tannin staining risk is managed through design (drainage, sealing).
  • The budget and extended lead time have been accepted for a premium tropical solution.

Merbau is NOT the right choice when:

  • Strict PHPP or nZEB targets demand the lowest possible Uw – λ 0.19 W/m·K is a real thermal penalty.
  • Adjacent surfaces are decorative concrete, natural stone, or light‑coloured ceramics – tannin staining will be permanently visible.
  • Budget or lead time are the primary constraints – European hardwoods or Accoya offer a better cost/time balance.

Frequently Asked Questions

Active tannin. Rainwater extracts tannin from the wood, which can bleed onto adjacent concrete, stone, or ceramic surfaces, leaving red‑brown marks. This is prevented by careful drainage, correct joint sealing, and complete finishing of the wood. It cannot be eliminated 100% – it is the natural chemistry of the species.

For hardness and natural durability, yes – Janka 7 620 N vs 4 980 N, Class 1‑2 vs Class 2. Thermally they are very close (λ 0.19 vs 0.18). Oak is more accessible from stock and costs less. Merbau requires extra precautions for tannin staining, so the decision depends on the project’s specific wear requirements and exposure.

Legally no, but highly recommended. Intsia bijuga appears on the IUCN Red List as Vulnerable. FSC-certified merbau is available on request, and we discuss its availability for every Merbau order during quoting.

815 kg/m³ vs 405 kg/m³ for spruce – roughly double for the same dimensions. A typical 1000×1200 mm sash on an IV92 profile weighs about 30 kg in Merbau compared to 15 kg in spruce. Our standard Roto hardware covers this load, but verification for the exact size is part of the quotation process.

λ ~0.19 W/m·K is among the highest in the compared range, so the merbau frame Uf is higher than that of spruce or meranti. Exact Uf, Uw, Ug, g-value and psi-spacer values for PHPP are provided on request for the specific configuration.

Contact and Quote

SC SM WOOD PRODCOM SRL – manufacturer of laminated wooden windows and doors, including made‑to‑order Merbau joinery.
Floresti, Ferma 9, Hala 8A, 407280, Cluj

  • www.smwoodprodcom.ro
  • Merbau windows and doors – made to order, premium tropical durability
  • Laminated wood IV92/D92 profiles – complementary series
  • FSC certified wood upon request
CONTACT US