Oak Wooden Windows - Premium Standard, Class 2

Oak Wooden windows – Class 2 Durability and Noble Appearance

European oak (Quercus robur) has the best natural durability of any European species in our range and the most expressive appearance under translucent stains. It is also one of the heavier species at 675 kg/m³, one of the harder at 4,980 N Janka, and has a higher thermal coefficient at λ 0.18 W/m·K compared to the standard European species in our range. These three facts define when oak is the right choice – and when it is not.

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Oak wood

Density 675 kg/m³

One of the heaviest standard species

Janka 4,980 N

One of the hardest standard woods

Durability Class 2

Best European durability

One of the Heaviest and Hardest European Hardwoods in our Range

Oak offers unmatched hardness and natural durability among European species. At 675 kg/m³ and 4 980 N Janka, it is the reference for high-traffic entrance doors and sill surfaces. Its λ 0.18 W/m·K sits at the upper thermal limit of our range, so specifying oak is always a balance between mechanical performance, aesthetic presence and energy efficiency.

Technical Data – European Oak

Property

Value

Density

675 kg/m³

Janka Hardness

4,980 N

Bending Strength

97.1 MPa

Modulus of Elasticity

10.6 GPa

Compressive Strength

46.3 MPa

Radial Shrinkage

4.7 %

Tangential Shrinkage

8.4 %

Volumetric Shrinkage

13 %

Thermal Conductivity (λ)

0.18 W/m·K

Natural Durability Class

2 (durable)

What these figures mean for joinery: an oak sash is significantly heavier than spruce (405 kg/m³) or meranti (480 kg/m³), and the hardware is sized accordingly. λ 0.18 W/m·K gives a higher Uf, so the final Uw may sit at the upper nZEB limit. Janka 4 980 N makes oak well suited to high-traffic entrance doors and sill surfaces. Class 2 durability gives a sensible safety margin for delayed maintenance. Radial shrinkage of 4.7% is close to meranti, so laminated oak profiles stay stable.

Performance in Windows

Oak offers a unique combination of mechanical strength, natural beauty, and genuine durability.

1

Thermal

λ 0.18 W/m·K is the highest in our standard range, so the oak frame Uf is higher than spruce (0.11 W/m·K) or meranti (0.13 W/m·K). nZEB compliance is achievable, though at the upper limit. Exact Uf and Uw values are supplied on request for PHPP.

2

Hardness

Janka 4 980 N means oak covers high-traffic thresholds, internal sills and heavy-use doors without visible marking. After years of use, the difference from spruce (1,680 N) or meranti (2,460 N) is unmistakable.

3

Finish

Under translucent stains, oak’s coarse grain, medullary rays and olive-brown tones are unmatched in our range. An opaque RAL finish hides the grain completely, so choosing oak for an opaque finish is a purely technical decision driven by hardness and durability.

Long‑term Performance

Oak’s Class 2 durability and high tannin content call for straightforward, well-understood care.

Natural Durability

Class 2 means untreated oak lasts longer than softwoods. A finish is still recommended, but the safety margin for delayed maintenance is significantly better than spruce or pine.

Tannin Management

The Remmers finish in 4+ layers blocks oak tannin. Our hardware is stainless steel or anti‑corrosive. The only precaution: installers must use stainless or galvanised screws in any raw wood left exposed after cutting.

Maintenance

10‑year cycle with light cleaning and re‑coating. The Remmers finish is formulated to work with tannin‑rich hardwoods. Oak is durability Class 2, and a maintained finish extends that considerably.

Lamination in 3+ layers neutralises the natural tendency of oak to warp. A well‑finished laminated oak profile is dimensionally stable and behaves predictably alongside other laminated species.

Advantages of Oak

Advantages

  • Natural Durability Class 2 – the most rot‑resistant European species in our range
  • Janka 4 980 N – well suited for high‑traffic thresholds and sills
  • Incomparable appearance under translucent stains – coarse grain, medullary rays, warm tones
  • High weight gives entrance doors a sense of solidity and substance
  • Standard stock species – no extended lead time, available on all main series

Disadvantages

  • λ 0.18 W/m·K – the highest thermal coefficient in the range, raises Uf above all other species
  • Heavier sashes – more stress on hinges; hardware must be verified for large sizes
  • Tannin can react with ordinary iron – stainless steel or anti‑corrosive hardware is mandatory
  • Higher cost compared to softwoods – reflects the lower yield of grade‑I wood from oak logs
Request a Quote for Oak Joinery

Comparison with Other Essences

How European Oak compares to the key alternatives in our joinery range.

Oak vs Spruce

Spruce wins on thermal performance (λ 0.11 against 0.18) and on cost. Oak wins on hardness (4 980 against 1 680 N), durability (Class 2 against 4) and appearance. For opaque nZEB projects, spruce is the logical choice; for a visible-grain, high-traffic solution, oak is unmatched.

Oak vs Meranti

Meranti is thermally better (λ 0.13). Oak wins on hardness, durability, and grain character. Dark Red Meranti can approach oak visually, but the European grain and solidity of oak remain a different tier for traditional projects.

Oak vs Scots Pine

Scots pine is thermally far superior (λ 0.13) and cheaper. Oak wins on hardness, durability, and visual presence. For an opaque‑finished window where thermal budget matters, pine is better. For a statement entrance door, oak is the answer.

Appearance and Colour

Heartwood is light to medium brown with an olive tint, varying noticeably from batch to batch. Sapwood is pale and not always sharply defined. The coarse, uneven grain and large medullary rays create a unique character – silvery streaks in radial sections, fine dots in tangential cuts. Under translucent stains, oak is the most expressive species in our range. Under opaque RAL paint, the appearance is identical to any other wood.

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  • Profil stratificat Stejar
  • Profil + textura + structura Stejar
  • Structura microscopica Stejar
  • Textura lemnului Stejar

Availability & SM WOOD Execution

Key Details

  • Standard stock species – available on IV68, IV78, IV92, D68, D78, D92, and internal doors.
  • Lead time 8‑12 weeks – identical to softwoods, no additional delay for the species itself.
  • FSC not mandatory (IUCN least concern); available on request.
  • Price reflects low yield of grade‑I wood from oak logs – the customer pays for the essence itself.
Contact us for Oak availability

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

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

Oak is the right choice when:

  • The main entrance door needs high traffic resistance and a sense of solidity.
  • Windows with visible oak grain are part of the architectural language (traditional, historic, natural‑material design).
  • Internal sills or thresholds require the maximum wear resistance in the standard range.
  • The client wants the best European durability in the range, accepting the thermal trade‑off.

Oak is NOT the right choice when:

  • The project demands the lowest possible Uw for nZEB or PHPP – spruce or pine are thermally superior.
  • Budget is the primary constraint – softwoods meet the functional requirement at a lower cost.
  • The finish is RAL opaque – the oak grain disappears, leaving only the thermal penalty.
  • Very large sashes are required – the extra weight stresses hinges, even though hardware is sized accordingly.

Frequently Asked Questions

Yes. Natural Durability Class 2 means untreated oak lasts much longer outdoors than softwoods (Class 4). A finish remains recommended, but the tolerance for delayed maintenance is far superior.

The production yield is low – a proportionally smaller amount of grade‑I wood is obtained from an oak log. The cost reflects the raw material, not a markup.

Yes. 2,000+ RAL colours are available. With an opaque finish the oak grain is hidden – the choice of oak is then purely technical, for hardness and durability.

No – the Remmers finish in at least 4 layers blocks the tannin. Our hardware (Roto, Simonswerk, Hoppe) is stainless steel or anti‑corrosive. Installers must use stainless or galvanised screws in any raw wood exposed after cutting.

No. Radial shrinkage (4.7%) is close to meranti (4.1%) and lower than pine (5.2%). Lamination in 3+ layers neutralises warping in oak just as it does in any of our species – we never manufacture windows from simple solid wood.

λ 0.18 W/m·K is the highest in our range, so the oak frame Uf is higher than spruce or meranti for the same profile. Exact PHPP values (Uf, Uw, Ug, g-value, psi-spacer) are provided on request for your configuration.

Contact and Quote

SC SM WOOD PRODCOM SRL – manufacturer of laminated wooden windows and doors, including European Oak joinery from standard stock.
Floresti, Ferma 9, Hala 8A, 407280, Cluj

  • www.smwoodprodcom.ro
  • European Oak windows and doors – in stock, 8‑12 week delivery
  • Laminated wood IV78/IV92 series – complementary profiles
  • FSC certified wood available on request
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