---
title: "OSB — density, melting point and properties"
description: "OSB has a density of 640 kg/m³ (600–680). Melting point, strength, conductivity, what it is used for, and whether it floats, rusts or is magnetic."
url: https://atoneplace.net/material/osb/
site: "At One Place"
---

# OSB

**Density of OSB: 640 kg/m³ (600–680)**

0.64 g/cm³ · 40.0 lb/ft³

Large wood strands laid in aligned layers and pressed with resin, designed as a cheaper structural replacement for plywood and rated for the same sheathing jobs. It is made from fast-growing small-diameter timber that could never be peeled into veneer, which is the economic point. Its weakness is water at the edges: OSB swells irreversibly when soaked and does not recover its thickness on drying, so cut edges on site need sealing.

## Properties

- **Density:** 640 kg/m³ (600–680) — 0.64 g/cm³
- **Young's modulus:** 5 GPa
- **Floats in water:** Yes
- **Magnetic:** No

## What it is used for

- Roof, wall and floor sheathing
- I-joist webs
- Site hoarding and temporary flooring
- Packaging cases and pallets

## How it compares

*Water is 1,000 kg/m³. Anything with a shorter bar than water floats in it.*

- air: 1.2 kg/m³
- expanded polystyrene foam: 20 kg/m³
- rigid polyurethane foam: 40 kg/m³
- OSB: 640 kg/m³
- Water — the float line: 1,000 kg/m³
- tungsten: 19,250 kg/m³
- gold: 19,300 kg/m³
- platinum: 21,450 kg/m³

*Water is 1,000 kg/m³. Anything below that floats.*

| Material | Density | Relative to water |
| --- | --- | --- |
| rigid polyurethane foam | 40 kg/m³ | 0.04× |
| expanded polystyrene foam | 20 kg/m³ | 0.02× |
| air | 1.2 kg/m³ | 0.00× |
| OSB ← | 640 kg/m³ | 0.64× |
| platinum | 21,450 kg/m³ | 21.45× |
| gold | 19,300 kg/m³ | 19.30× |
| tungsten | 19,250 kg/m³ | 19.25× |

## Does it rust?

OSB contains no iron, so it cannot rust. Whether it degrades depends on the material, not on oxidation.

## Is it magnetic?

OSB is not a metal and has no ferromagnetic response.

## Common questions

### What is the density of OSB?

640 kg/m³ (600–680), or 0.64 g/cm³.

### Does OSB float?

Yes. At 640 kg/m³ it is less dense than water's 1,000.

### Is OSB magnetic?

OSB is not a metal and has no ferromagnetic response.

## Related pages

- [Does OSB float?](https://atoneplace.net/does-it-float/osb/)
- [Pine](https://atoneplace.net/material/pine/)
- [Plywood](https://atoneplace.net/material/plywood/)
- [MDF](https://atoneplace.net/material/mdf/)
- [White oak](https://atoneplace.net/material/white-oak/)
- [Red oak](https://atoneplace.net/material/red-oak/)
- [Balsa](https://atoneplace.net/material/balsa/)
- [Spruce](https://atoneplace.net/material/spruce/)
- [Western red cedar](https://atoneplace.net/material/cedar/)

## Sources

- Typical range compiled from manufacturer specifications — At One Place (/about/)