What is balsa wood?
The Wood Guide · The wood register
Broadleaf wood · referenceBalsa wood
Botanically a hardwood, in practice lighter than cork. The Spanish word balsa means raft — and that says it all.
- Ochroma pyramidale
- 150 kg/m³
- 18–28 m in a few years
Balsa treeOchroma pyramidale
Balsa in brief
A curiosity with serious uses: the lightest commercially traded wood in the world, and also a core material in wind turbine blades.
With an average dry density of 150 kg/m³, balsa weighs about a third as much as spruce and is even lighter than cork. That comes down to its cell structure: extremely large, thin-walled cells that contain mostly air. So it is not a weak wood, but a wood that weighs almost nothing.
Botanically, balsa is a broadleaf tree. That surprises people, but it shows why the split into hardwood and softwood says nothing about hardness: it is about the botanical group, not the density.
Balsa trees grow to 18–28 metres tall in a few years, with a trunk diameter of 1 to 1.2 metres. That speed makes plantation balsa relatively quick to renew — one of the few tropical species where that argument really holds.
- Botanical
- Ochroma pyramidale
- Origin
- tropical America, today mainly from plantations
- Dry density
- around 150 kg/m³ — the lightest commercial timber
- Modulus of elasticity
- 3.71 GPa
- Growth
- 18–28 m in a few years
- Botanical group
- hardwood — despite its softness
To be fair: balsa is so soft that a fingernail leaves a dent. It is unsuitable for anything that gets handled, loaded or put outside; it is a technical and hobby material, not a furniture wood.
The lightest commercial timber
With a dry weight of around 150 kg/m³, balsa is the lightest commercially traded wood in the world. For comparison: spruce is around 450, oak around 700, azobé above 1000. In water, balsa therefore floats high — life rafts and surfboards owed their buoyancy to it.
Click a chapter or use the arrows · floating depth derived from density, cells and growth schematic.
Why that lightness is useful
Extremely light
Around 150 kg/m³. For comparison: spruce is around 450, oak around 700, azobé above 1,000.
Springy
Despite its softness, a modulus of elasticity of 3.71 GPa — it bends and springs back rather than breaking.
Insulating
All those air pockets make it excellent for sound, heat and vibration insulation.
Buoyant
The Spanish word balsa means raft. Life rafts and surfboards owed their buoyancy to it.
The answer to the most common question: you cannot sit on it. Balsa is too soft and not durable enough for outdoor use. We include it in the register because it shows the extremes of the world of wood, not because we work with it.
Where balsa is really used
| Use | Why balsa | Distinctive |
|---|---|---|
| Model making | Ultralight, easy to cut with a craft knife | The classic use: model aircraft |
| Wind turbine blades | Core material in sandwich construction | Stiffness without weight — the largest industrial market |
| Aviation | Core material in composite panels | Same principle as in turbine blades |
| Water sports | Buoyancy | Surfboards, life rafts |
| Musical instruments | Lightweight parts | Limited, in guitar making |
| Fishing | Lightweight lures | Floats by itself |
The same material children build model aircraft from sits as the core of wind turbine rotor blades. Sandwich construction: two stiff outer skins with a light core in between give stiffness at minimal weight.
Frequently asked questions about balsa wood
Is balsa a hardwood or a softwood?
Botanically, balsa is a broadleaf tree, and therefore a hardwood. The fact that it is the softest wood in the world shows exactly why that classification is confusing: it is about the botanical group, not hardness. See hardwood versus softwood.
Why is balsa so light?
Because of its cell structure: extremely large cells with very thin walls, so the volume consists mostly of air. That gives around 150 kg/m³, against 450 for spruce.
Can balsa wood go outdoors?
No. It is too soft and not durable enough. For outdoor use, look at class 1 or 2.
Is balsa grown sustainably?
Usually, yes: most of it comes from plantations, and the trees reach harvestable size in a few years. That makes it one of the fastest-renewing tropical woods.
Balsa in perspective
The light extreme of the wood register — with azobé at the other end.
Have a question about your project? Just ask — we're happy to help.
Ochroma pyramidale — Joseph Francis, CC BY 2.0 · Ochroma pyramidale — Jonn Leffmann, CC BY 3.0 · Ochroma pyramidale — BrickArt!san, CC BY-SA 2.0 · Photo via Wikimedia Commons: Ochroma pyramidale — David J. Stang, CC BY-SA 4.0