What is oak?
The Wood Guide · The wood register
Broadleaf wood · referenceOak
Not a passing fashion. For centuries the choice for the sturdiest structures, the finest furniture and the most durable floors — and not without reason.
- Quercus robur · Quercus petraea
- 670–760 kg/m³ — heavy
- Class 2 · 15–25 years outdoors
Pedunculate oakQuercus robur
Oak in brief
Hardness, natural toughness and a pronounced grain — that combination makes oak one of the most reliable wood species you can choose.
Oak does not bend easily under load, resists scratches and dents, and moves less than softwood when humidity changes — provided it has been properly dried and worked. The end grain, with its growth rings and rays, is the signature of this species: no other European wood is so recognisable.
To be honest: we do not build our garden furniture in oak — for that we use teak, acacia and other hardwood. Oak is here because you come across it everywhere and it deserves a proper explanation. We do, however, have wood oil in a dark oak colour for anyone after that shade.
- Botanical
- Quercus robur, Quercus petraea
- Colour
- light brown to honey brown, darkens over time
- Density
- 670–760 kg/m³ (at 12% moisture)
- Hardness
- 6,490 N (European) · 6,050 N (American)
- Outdoors
- class 2 — 15–25 years (heartwood)
- Maintenance
- oiling, or simply letting it age
- Price range
- investment
Fair is fair: oak is full of tannic acid — combined with iron or rain it can turn black. Galvanised or stainless steel fittings are no luxury with oak.
Three species that matter in the trade
The genus Quercus has more than five hundred species worldwide. Three are relevant to the timber industry — and they differ noticeably.
| Species | Scientific name | Characteristics | Uses |
|---|---|---|---|
| European oak | Quercus robur, Q. petraea | Dense, hard, pronounced grain, durable | Furniture, floors, building structures |
| American white oak | Quercus alba | Slightly softer than European, lighter shade | Furniture, joinery, wine barrels |
| Red oak | Quercus rubra | Reddish shade, fast-growing, coarser grain | Furniture industry, interior panels |
For a closer look at the difference between European and American oak, read what is oak, European and American.
Physical and mechanical properties
Oak scores well on almost every technical measure. For those who take materials seriously.
| Physical | Value |
|---|---|
| Density (12% moisture) | 670–760 kg/m³ |
| Janka hardness, European | 6,490 N |
| Janka hardness, American | 6,050 N |
| Radial shrinkage | 4% |
| Tangential shrinkage | 7.7% |
| Mechanical | Value |
|---|---|
| Modulus of elasticity | 11,700 N/mm² |
| Bending strength | 88 N/mm² |
| Compressive strength | 52 N/mm² |
New techniques
The sector does not stand still. Three developments worth knowing about.
Thermal modification
Oak is heated to 160–230 °C, without chemicals. The result: more stable, more moisture-resistant wood with a deeper colour.
Engineered oak
Thin layers of solid oak on a stable core. Less wood per product, while keeping the authentic look.
New coatings
Ultra-thin protective layers that make the wood water-repellent and scratch-resistant without masking its natural appearance.
What you can do with oak
Few wood species are so versatile: from heavy load-bearing structures to fine cabinetmaking.
Building and construction
Beams, trusses and timber-frame structures, cladding and roof structures, floors and stairs — solid or as parquet.
Furniture and interiors
Dining tables, chairs and cabinets, beds, kitchens and worktops, doors and window frames.
Wine barrels
American white oak is the standard in the wine world: its tannin structure contributes to the ageing process.
Shipbuilding
Historically the backbone of the European fleet, and still used today for wooden vessels.
Musical instruments
For specific parts of percussion and string instruments.
An oak stores CO₂ throughout its growing life, and a long life as furniture or flooring extends that storage. Solid oak lasts for decades, which greatly lowers its footprint per year, and at the end of its life it can be composted or used as biomass. When buying, ask where the wood comes from — a supplier who is clear about that tells you more than a label.
Tannic acid: the black stains explained
Anyone who has ever fixed an oak tabletop with ordinary screws knows the phenomenon.
Oak contains a high level of tannic acid, also called tannins. That tannic acid reacts chemically with iron to form iron tannate: a dark, almost black compound. Rainwater running over an iron screw in oak draws that colour into the board — and you will never get it out again.
Use stainless steel, aluminium or brass fixings for anything that goes into oak. The same advice applies, by the way, to acacia, which is also rich in tannic acid.
Maintaining oak
Oak asks for little, but doing nothing is not a strategy either. A simple routine is enough.
| Use | Method | Frequency |
|---|---|---|
| Indoor furniture | Dust, clean with a slightly damp cloth | Weekly to monthly |
| Oak floors | Vacuum, mop with a neutral product | Weekly |
| Outdoor uses | Clean thoroughly, treat with oil or stain | Yearly |
For outdoor work in oak, the same principles apply as for other wood you want to keep in colour — the approach is set out in our maintenance guide.
Frequently asked questions about oak
Is oak suitable for outdoor use?
European oak reaches durability class 2 — moderately durable to durable — and can be used outdoors, provided you treat it every year with a suitable oil or stain. In direct contact with the ground or in permanently damp conditions it needs more intensive maintenance.
Why does oak turn black in contact with metal?
Because of its high tannic acid content. It reacts with iron to form iron tannate, an almost black compound. Use stainless steel, aluminium or brass screws and fixings, and the problem does not exist.
What is the difference between red oak and white oak?
Red oak (Quercus rubra) has a reddish shade, a coarser grain and open pores, which makes it less water-resistant. White oak (Quercus alba) has tyloses in its vessels — small cell structures that seal the pores — which makes it denser, more water-resistant and better suited to barrels and outdoor work. More in European and American oak.
How long does solid oak last?
With proper maintenance, easily 50 to 100 years, and historical examples last for centuries. The key lies in protection against prolonged moisture and periodically treating the surface.
Do you sell oak garden furniture?
No. We make our garden furniture in pressure-treated softwood and in hardwood such as teak, acacia and meranti. Oak is in The Wood Guide because it is one of the best-known wood species and you come across it everywhere — not because we sell it.
Comparing oak
Oak is one of the twelve species in our register. If you are looking for garden furniture with comparable solidity, take a look at hardwood.
Have a question about your project? Just ask — we're happy to help.
Quercus robur — Sten Porse, CC BY-SA 3.0 · Quercus — Olivier Lemoine, CC BY-SA 3.0 · Quercus — William Warby, CC BY 2.0 · Photo via Wikimedia Commons: Quercus robur — AnRo0002, CC0