Cork is the bark of the cork oak (Quercus suber), a tree grown mainly in Portugal and Spain. The bark can be stripped from the living tree and then grows back; harvesting takes place at intervals of about nine years. The cells of cork are filled with air, which makes the material light, resilient and insulating.
Properties
- Insulating — expanded cork board has a thermal conductivity of roughly 0.040 W/(m·K), comparable with mineral wool
- Resilient — cork springs back after being compressed, which makes it suitable as a vibration and impact sound damping layer
- Moisture tolerant — it absorbs little water and does not rot readily
- Renewable — the tree does not have to be felled to obtain it
Cork products in construction
| Product | Description | Use |
|---|---|---|
| Expanded cork board (ICB) | Cork granulate expanded with steam and bonded by its own resin | Wall, roof and floor insulation |
| Cork granulate | Loose granules | Filling cavities and voids |
| Cork flooring and tiles | Pressed cork with a wear layer | Floor finish |
| Cork rubber and cork strip | Cork bound with rubber | Vibration damping under machinery and screeds |
Using cork in practice
- Floor finish — cork floors feel warm underfoot and deaden footfall noise; in wet areas choose a version with a water-resistant wear layer
- Impact sound — a thin cork layer under a floating screed or laminate reduces impact sound transmitted to the room below
- External insulation — expanded cork board is used as an insulation carrier behind render, including on historic buildings where a vapour-open build-up is wanted
- Cost — cork is more expensive than EPS or mineral wool; the premium over the cheapest insulation can be several times over. Judge whether the additional properties justify the outlay
Note that cork is combustible. Check the reaction to fire class required for the application.
Related terms
- Insulation material
- Thermal conductivity
- Impact sound
- Floating screed
- Vapour open
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