Kingspan Kooltherm K3 Floorboard Underfloor Insulation
25mm - R1.10 (12 boards per pack, 34.56 m²)
$778.50
Sale price
$778.50
Regular price
$865.00
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Kingspan Kooltherm K3 Floorboard Underfloor Insulation
$778.50
Sale price
$778.50
Regular price
$865.00
GST inclusive
This size is on sale. Sale items are not included in the Opening Offer order discount. Offer details
How many do you need?
Measure the wall, ceiling or roof area and take about 10% off for studs, joists and purlins.
You need
Which covers
Total
Dispatch: Most orders are processed the same day. Metro delivery: Usually 1–3 business days. We do our best to get most items out on the next business day.
Delivery to VIC and NSW: $55 in metro Melbourne and metro Sydney, $99 in the outer ring around both cities, $149 anywhere else in the two states · Local pickup from Epping, VIC by arrangement · Shipping details
Kingspan Kooltherm K3 Floorboard is a rigid phenolic floor insulation board, R1.10 at 25 mm and R2.30 at 50 mm, made by Kingspan at Somerton in Victoria. It goes under a concrete slab on ground, or over the slab beneath a screed with hydronic heating.
Which thickness
Kingspan's 7 Star guide for Victoria and New South Wales uses the 50 mm board in its slab on ground and suspended timber floor examples. On a real job, the energy rating or the designer's floor calculation sets the thickness.
A product R-value, not the floor's
R1.10 and R2.30 are product R-values for the board alone. What the finished floor achieves depends on the slab and the ground or sub-floor space below it, and Kingspan points to NCC 2022 Specification 39 or CIBSE Guide A Section 3.5 to work it out. Keep the board off bare subsoil and out from under point loads and foundations, slab thickenings included.
Packs and coverage
Boards are 2400 x 1200 mm and come in Kingspan's full packs: 12 boards of 25 mm covering 34.56 m², or 6 boards of 50 mm covering 17.28 m². Both thicknesses are stocked.
On site
Lay a polythene DPM of at least 300 micron first. Loose-lay the boards break-bonded with the joints lightly butted, then cover them with polythene of at least 125 micron, laps of 150 mm taped, so wet concrete cannot get into the joints. Wet boards should not be used, so keep packs covered. Avoid solvent adhesives containing methyl ethyl ketone. Full figures are in the table below.
Technical data
Kingspan technical data sheet (PDF)Sizes stocked
| Thickness | Product R-value | Board size | Boards per pack | m² per pack | Product code | Supply |
|---|---|---|---|---|---|---|
| 25 mm | R1.10 | 2400 x 1200 mm | 12 | 34.56 m² | 100000065289 | Stocked |
| 50 mm | R2.30 | 2400 x 1200 mm | 6 | 17.28 m² | 100000065291 | Stocked |
Thermal
| Declared product R-value at 23 °C, 25 mm | R1.10 |
|---|---|
| Declared product R-value at 23 °C, 50 mm | R2.30 |
| Thermal conductivity, 25 mm board | 0.023 W/m.K at 23 °C (insulant 25 to 44 mm) |
| Thermal conductivity, 50 mm board | 0.022 W/m.K at 23 °C (insulant 45 mm and over) |
| Conductivity test standard | AS/NZS 4859.1:2018 / ASTM C518-2017 |
| Total R-value of the floor | Calculated for the construction, to NCC 2022 Specification 39 or CIBSE Guide A Section 3.5 |
These are product R-values for the board alone. The floor's total depends on the slab and the ground or sub-floor space below it.
Fire
| Early fire hazard (AS 1530.3:1999) | Spread of Flame Index 0, Smoke Development ≤ 3 |
|---|---|
| Smoke obscuration (Kingspan specification clause) | Tested smoke obscuration of not more than 100 m²/kg |
Vapour and moisture
| Water vapour | Resistant to the passage of water vapour |
|---|---|
| Water Vapour Transmission (ASTM E96 Part B - 2016) | > 35 MN.s/g |
| Vapour control layer over the boards | Polythene sheet of at least 125 micron / 500 gauge, overlaps 150 mm and taped |
Loads and limits of use
| Compressive stress (AS 2498.3:1993) | Typically exceeds 120 kPa at 10% compression |
|---|---|
| Floor screeds | Un-reinforced screeds can be used over it in most applications |
| Heavy floor loads | Refer to Kingspan Technical Services, 1300 247 235 |
| Point loads and foundations | Not to be placed under direct point loads or foundations, including slab thickening |
| Subsoil | Not for direct contact with subsoil, must be used over a DPM |
| Solvents | Core is not resistant to some solvent-based adhesives, particularly those containing methyl ethyl ketone |
Material and handling
| Core | Fibre-free rigid thermoset closed cell phenolic |
|---|---|
| Facings | Tissue based facing on both sides (glass tissue) |
| Blowing agent | Zero ODP and low GWP |
| Board size | 2400 x 1200 mm (2.88 m²) |
| Packaging | Labelled packs, shrink-wrapped in polythene |
| Storage | Inside a building, or stacked clear of the ground under an opaque polythene sheet or weatherproof tarpaulin |
| Cutting | Fine toothed saw, or score with a sharp knife, snap over a straight edge and cut the facing on the other side |
| Made in | Australia, at Kingspan's Somerton plant in Victoria |
Boards that have got wet, are damaged or have touched harsh solvents or acids should not be used.
Compliance
| Standards | NCC and AS/NZS 4859.1:2018 compliant |
|---|---|
| Installation | AS 3999:2015 Bulk Thermal Insulation Installation and AS 3000:2018 Wiring Rules |
| Management systems | ISO 9001:2015, ISO 14001:2015, ISO 45001:2018, ISO 50001:2018 |
| EPD | EPD-IES-0014111:002 (International EPD System, EPD Australasia), valid until 12 December 2029 |
| Warranty | 10 years against manufacturing defects from installation, residential and commercial, subject to the Kooltherm warranty terms (KIAU0190) |
The warranty needs installation by a qualified tradesman to Kingspan's instructions and is not transferable.
Fitting notes
Build the foundations to DPC level, using a thin sand blinding over rolled aggregate if a level surface is needed. Lay a polythene damp proof membrane of at least 300 micron (1200 gauge) over well compacted aggregate, with the joints well lapped and folded, and bring it up the walls far enough to meet or form the DPC. Loose-lay the boards break-bonded with the joints lightly butted. Where two layers are needed, offset them so the joints do not line up. Cover the boards with polythene of at least 125 micron (500 gauge), with 150 mm overlaps taped, to keep wet concrete out of the joints and act as a vapour control layer. Where K3 is also used vertically at the slab edge, the DPM goes on its outside face. Protect the boards from foot and barrow traffic with scaffold planks or similar while the slab goes in, and let the slab and screed dry before laying the floor finish. Cut with a fine toothed saw, or score with a sharp knife, snap over a straight edge and cut the facing on the other side. Install to AS 3999:2015 and AS 3000:2018.
Figures are taken from the Kingspan data sheet for Kooltherm K3 Floorboard, KIAU0054 Issue 11, September 2023. Pack quantities are from Kingspan's VIC and NSW 7 Star guide, KIAU0216 Second Issue, February 2025, the facing material from the Kooltherm safety data sheet KIAU0179, the EPD details and production site from EPD-IES-0014111:002 and the warranty from KIAU0190 Sixth Issue, April 2024. The manufacturer document is linked above. Kingspan can change specifications without notice, so check the current sheet before specifying on a job.
Common questions
Does K3 go under the slab or on top of it?
Either. Kingspan's data sheet shows it below a concrete slab on ground, laid over a DPM, and above the slab under a screed with hydronic underfloor heating. Un-reinforced screeds can be used over it in most applications, but ask Kingspan Technical Services first where floor loads will be heavy.
What R-value do I actually get?
Kingspan declares R1.10 for the 25 mm board and R2.30 for the 50 mm board at 23 °C. Those are product R-values for the board alone. The total for the floor depends on the slab and the ground below it, and Kingspan points to NCC 2022 Specification 39 or CIBSE Guide A Section 3.5 for the calculation.
How much does one pack cover?
Each board is 2400 x 1200 mm, or 2.88 m². A pack of 25 mm holds 12 boards and covers 34.56 m². A pack of 50 mm holds 6 boards and covers 17.28 m².
Can it sit straight on the ground or under the footings?
No to both. Kingspan says the board is not for direct contact with subsoil and must be laid over a DPM of at least 300 micron (1200 gauge) polythene. It must not go under direct point loads or foundations, including slab thickening.
Do the boards need polythene over them before the pour?
Yes. Kingspan's instructions call for a polythene sheet of at least 125 micron (500 gauge) over the boards, with 150 mm overlaps taped. It stops wet concrete running into the board joints and acts as a vapour control layer.
Can I use K3 in a suspended timber floor?
Kingspan's VIC and NSW 7 Star guide shows 50 mm K3 between the joists of a suspended timber floor, and its residential floor flyer draws the board between timber floor joists on 25 x 25 mm timber support battens. The K3 data sheet does not give a fixing method for that use, so check the detail with Kingspan Technical Services on 1300 247 235.
Which adhesives can I use with it?
Avoid solvent-based adhesives, particularly those containing methyl ethyl ketone, because Kingspan says the core is not resistant to them. The core does handle short-term contact with petrol and most dilute acids, alkalis and mineral oils, but clean any spill off before the boards go down.
What warranty does it carry?
Kingspan warrants Kooltherm K3 against manufacturing defects for 10 years from installation, for residential and commercial work. The terms require installation by a qualified tradesman to Kingspan's instructions, and the warranty is not transferable.
Cannot see your question? Ask our team and we will get you an answer.
Answers use the Kingspan data sheet for Kooltherm K3 Floorboard (KIAU0054 Issue 11, September 2023), Kingspan's VIC and NSW 7 Star guide (KIAU0216 Second Issue, February 2025) and residential floor flyer, and the Kooltherm product warranty (KIAU0190 Sixth Issue, April 2024).
