Description
A roof insulation material that breathes as well as it insulates
Most rigid roof insulation forces a choice: get the thermal performance you need, or keep the roof build-up breathable enough to avoid trapping moisture in old timber, lime-rendered walls or a period conversion. Expanded cork insulation board is one of the few materials that does not force that trade-off. Pressed from cork-oak granules using nothing but the tree's own natural resin as a binder, it insulates, dampens sound and lets a roof structure manage moisture vapour the way it was built to — which is exactly why timber-frame builders, eco-renovators and conservation-minded roofers keep specifying it on jobs where foil-faced foam board is the wrong answer.
Each board is cut to a full 1000 x 500mm and supplied in factory packs, so an order maps directly onto the area you are covering rather than a guessed quantity of loose sheets. Use it between and over rafters on a warm or cold pitched roof, as a breathable overlay on a flat roof deck, or anywhere a natural, vapour-permeable insulant needs to sit alongside timber, lime or masonry without introducing a vapour barrier the rest of the build-up cannot cope with.
Key benefits
- 100% natural expanded cork – no added chemical binders, resins or blowing agents
- Vapour-permeable construction that supports breathable, moisture-safe roof and wall build-ups
- Low thermal conductivity (λ 0.037–0.040 W/m·K) for genuine year-round thermal performance
- Naturally flame-resistant, rot-resistant and dimensionally stable – no chemical fire retardants added
- Doubles as an effective acoustic and anti-vibration layer, useful under living roofs and habitable loft conversions
- Fully recyclable and biodegradable at end of life, harvested from cork oak bark without felling the tree
Suitable applications
Pitched and flat roof insulation between/over rafters, breathable warm-roof and cold-roof build-ups, timber-frame roof and wall sarking, insulation retrofits on solid masonry and lime-rendered buildings, acoustic decoupling under roof terraces and living roofs, and any application calling for a natural alternative to PIR or PU foam board.
Specification
| Pack | Board size | Boards per pack | Coverage | Thermal conductivity |
|---|---|---|---|---|
| 10mm | 1000 x 500mm | 30 | 15m² | λ 0.037–0.040 W/m·K |
| 40mm | 1000 x 500mm | 8 | 4m² | λ 0.037–0.040 W/m·K |
| 50mm | 1000 x 500mm | 6 | 3m² | λ 0.037–0.040 W/m·K |
Frequently asked questions
Is cork board a like-for-like swap for PIR or PU foam board?
Not quite – cork is vapour-permeable where PIR is not, so it belongs in a breathable build-up rather than a sealed warm-roof system. For a foil-faced, high-performance warm-roof board, see our PIR Insulation Board instead; for a breathable timber-frame alternative closer to cork's own performance profile, see our Wood Fibre Sarking & Insulation Board.
Can it be fixed directly to solid masonry?
Yes, using a lime-based adhesive mortar rather than a cement- or gypsum-based product, so the wall keeps its ability to breathe. A registered installer or your building control adviser can confirm the right fixing spec for a listed or solid-wall building.
Does it need a separate breather membrane over the top?
On most pitched roof build-ups, yes – pair it with a Breathable Roofing Membrane above the rafters to shed any incidental moisture while still allowing the structure to dry.
How many boards will I need?
Measure the total area in square metres and choose the thickness pack (or combination of packs) whose coverage meets or slightly exceeds it – the table above gives the exact coverage per pack for each thickness.
Is it treated with any chemical fire retardant?
No – cork's fire resistance is a natural property of the material itself, not an added treatment. No specific fire test certificate is quoted here; ask us for the manufacturer's datasheet if your project has a formal fire-rating requirement.
Ordering & installation guidance
Order the pack size that matches your measured area in square metres. Boards can be cut on site with a fine-tooth saw or bread knife to fit around rafters, joists and services. For a complete breathable roof build-up, pair Cork Insulation Board with our Breathable Roofing Membrane as an over-rafter layer, or compare it against our Wood Fibre Sarking & Insulation Board if a timber-fibre board suits your build-up better. For sealed warm-roof applications where vapour permeability is not required, our PIR Insulation Board offers higher thermal performance per millimetre.
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