PIR Production Challenges, and Price Increases
Unfortunately, further to the recent supply challenges with PIR and Phenolic insulation boards from Celotex, Kingspan, Ecotherm and Recticel, available stock of these product will vary throughout the country.
We will endeavour to source the required stock, however, we may need to mix and match equivalent products from multiple manufactures, suppliers and depots. This may affect the rates; we will of course discuss possible solutions with you before proceeding and will do our best to keep additional costs down.
Specialised insulation boards will be affected more than general application boards, so please allow additional time to process and deliver these orders.
Please allow extended lead times on PIR and Phenolic foam insulation.
Please, always check the availability ‘Star Rating’ that we place against each product line item, though depending on your geographical location, available products may vary from manufacturer to manufacturer.
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Celotex FI5000 Under Floor Heating Insulation - NEW!
Premium performance flooring insulation solution, suitable for concrete slab, beam and block, suspended timber and underfloor heating flooring applications.
Celotex's new FI5000 range of higher specification boards replaces FF4000 Range, and is purpose designed for use in internal underfloor, under-screed, heating applications. These boards have a higher compressive strength value of ≥175 kPa, which exceeds the standard GA4000 board range of (kPa) =≥140, making them more suitable to effectively retain the underfloor heating pipe clips in place, when the screed is poured over the underfloor heating system
Product Applications
Celotex FI5000 is a premium performance flooring insulation solution, suitable for a range of flooring applications including concrete slab, beam and block, suspended timber and underfloor heating applications.
FI5000 is suitable for concrete slab, beam and block, suspended timber and underfloor heating applications. FI5000 provides thermal performance benefits and has been designed with installation efficiency in mind. Featuring a super low lambda of 0.021W/mK, FI5000 achieves compliance to UK Building Regulations with better U-values and thinner solutions.
Celotex FI5000 combines best in class PIR insulation with an innovative composite facer featuring a built-in vapour control layer (VCL), enabling direct screed, without the need for an additional separating layer. FI5000 features an enhanced compressive strength value of ≥175 kPa making it the ideal solution for a range of flooring applications.
Board size: 1200 x 2400mm, Commonly available in thicknesses of 75mm, 100mm and 125mm.
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Click to Buy: Celotex FI5000 Underfloor Heating Insulation Boards - Supersedes FF4000
Procedure: Select products below to see pricing structure | Use product tick-boxes to select required products | Add to Basket
Our Prices are currently being revised – please contact us for the latest prices
1 plus rolls @ £0.14 per lm = £6.35 (£7.62 inc-VAT) per roll
5 plus rolls @ £0.14 per lm = £6.29 (£7.55 inc-VAT) per roll
10 plus rolls @ £0.14 per lm = £6.23 (£7.48 inc-VAT) per roll
15 plus rolls @ £0.14 per lm = £6.18 (£7.42 inc-VAT) per roll
20 plus rolls @ £0.14 per lm = £6.12 (£7.34 inc-VAT) per roll
25 plus rolls @ £0.13 per lm = £6.07 (£7.28 inc-VAT) per roll
Product Advantages
Celotex FI5000 provides thermal performance benefits and has been designed with installation efficiency in mind. Featuring a super low lambda of 0.021W/mK.
Celotex FI5000 combines best in class PIR insulation with an innovative composite facer featuring a built-in vapour control layer (VCL), enabling direct screed, without the need for an additional separating layer.
FI5000 features an enhanced compressive strength value of ≥175 kPa making it the ideal solution for a range of flooring applications.
Ensures minimal downward heat loss into structure
Has a highly resistant composite facer featuring a built-in vapour control layer (VCL), enabling direct screed, without the need for an additional separating layer.
Uses the foam structure to ensure better pipe clip retention
Is easy to cut and install
Future proofs the energy performance of new and existing buildings
Technical Data
Celotex FI5000 Underfloor Heating Insulation Boards
Product Code |
Board dimensions |
Thickness (mm) |
λ Value (w/mK) |
R-value (m²K/W) |
U Value (W/m²K) |
Weight (kg/m²) |
Unit weight (kg) |
Celotex FI5075 |
16 x 1.2 x 2.4 = 46.08m² |
75 |
0.021 |
3.55 |
0.28 |
3.36 |
53.76 |
Celotex FI5100 |
12 x 1.2 x 2.4 = 34.56m² |
100 |
0.021 |
4.75 |
0.21 |
4.32 |
51.84 |
Celotex FI5125 |
9 x 1.2 x 2.4 = 25.92m² |
125 |
0.021 |
5.95 |
0.17 |
5.28 |
47.52 |
Thermal conductivity / Lambda value (W/mK) = 0.021 | Compressive strength (kPa) = ≥ 175 | Dimensional stability (70,90)3 - DS(-20.-)1.
Please Note: R-Value = Thermal Resistance; U Value = Thermal Transmittance Co-efficient; Compressive strength = kiloPascals; Vapour resistance = MegaNewton seconds per gram.
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Celotex TB4025 / US4025 Floor Upstand Rigid PIR Insulation Boards
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Product Code |
Board dimensions
(16 boards per pack)
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Thickness (mm) |
λ Value (w/mK) |
R-value (m²K/W) |
U Value (W/m²K) |
Weight (kg/m²) |
16 Board weight (kg)
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Celotex TB4025 |
16 x 1.2 x 2.4 = 46.08m² |
25 |
0.022 |
1.10 |
0.91 |
0.73 |
33.64 |
New from Celotex ...
US4025 Upstand Insulation for concrete slab and beam & block flooring applications. More information to follow.
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Product Information and Certification
Links to manufacturer's information. Click to download in a separate browser window.
Celotex FI5000 Datasheet | Celotex Flooring Certification | Celotex Handy Guide
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Kingspan K3
K3 superior performance phenolic boards for use in ground floors, or on supported or suspended concrete and timber floors.

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Kingspan TF70
A range of performance rigid PIR boards used for insulation of solid concrete and suspended ground floors

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Celotex TB / XR4000
Celotex TB4000 and XR4000 rigid PIR boards for under-floor heating, floor insulation, and perimeter up-stands.
Product Installation
Celotex FI5000 products can be installed in accordance with these instructions
- Ensure that joist spacing is at no more than 600mm centres and that the dimension of the joist is sufficient to span and accept additional loads. If asphalt weathering is to be used, joists can be at no more than 400mm centres.
- Install the insulation boards, ensuring that the long edges are parallel to the line of the joists. 50mm x 50mm cross noggings can be inserted between joists to support the short edges of the boards.
- Where boards butt together, bed onto twin beads of vapour sealant wide enough to accommodate this arrangement. This completes the vapour control layer (VCL) when combined with each board’s foil facings.
- Lay the boards with the plywood side uppermost and stagger board joints. Leave a gap of approximately 2mm between boards and ensure a minimum 20mm bearing on joists and noggings.
- Fix Celotex FI5000 with corrosion-proof Suretwist Composite Panel helical fasteners at a frequency to suit the design wind load. Refer to BS 6399-2 Code of Practice for Wind Loads. As a guide, 16 fasteners per board will resist a wind load of 2.22 KN/m2 based on a design load of 0.4 KN per fastener.
- Ensure that fixings are no less than 10mm in from the board edge or 50mm from each corner. They can be equally spaced along the supporting joists. Fixings can be long enough to penetrate at least 38mm into the supporting timber.
- Stagger opposing fixings where two board edges share the same joist or noggin.
- Provide a complete insulation envelope by extending the wall insulation board up to the underside of the roof deck.
- Provide a soffit or ceiling below the joists, as the surface of the product is not designed to be used as a decorative internal finish.
- Ensure that the plywood is completely dry before any weathering system is applied.
- Always use a Type 3G felt to BS 747 as a vapour diffusion first layer when using BUR weathering systems. When using a single-ply membrane, additional 12mm plywood has to be applied on top of the Celotex FI5000.
- Temporary protection must be provided for both the insulation and the waterproofing, if significant foot traffic is anticipated either during or after installation.
Falls
- The structure can be designed so that the finished roof has a continuous, smooth and even slope towards the rainwater outlet or gutter. The minimum fall can be 1:80 to avoid ponding water.
Deck stability
- Celotex FI5000 incorporates exterior grade WBP plywood to BS 1203, laminated to the surface. This gives the product excellent strength. Boards can span up to 600mm joist centres to provide a suitable substrate for a variety of weathering systems.
Vapour control layer
- Celotex FI5000 has a built-in VCL due to the foil facers but this is discontinuous at the board joints. In some applications no further attention to moisture control may be necessary.
- Celotex would generally recommend the application of a vapour sealant between the tops of the boards at all edges. This is essential in areas of potentially high humidity.
Pre-installation guidelines for concrete slab floor applications only
- Install a damp proof membrane below the Celotex. This can either be over the top of or below the slab.
- The damp proof membrane must provide continuity with the damp proof course in the surrounding walls.
- Level the surface of the slab; it should be smooth and free of projections.
- If required, use a thin layer of sand blinding on a rough, tampered slab to ensure that the insulation boards are continuously supported. Use scaffold boards or other protection to prevent wheelbarrows and other traffic damaging the insulation.
Installation guidelines for concrete slab and beam & block floor applications
- Cut and fit Celotex US4025 insulation upstand to floor perimeter, to meet a minimum R-value of 0.75 m2K/W. The upstand depth should be equal to the sum of the slab insulation and the screed thickness. The upstand thickness should not exceed the combined thickness of the wall plaster and the skirting.
- Lay Celotex insulation boards across the damp proof membrane.
- They should be break bonded with board joints tightly butted and must be taped to ensure the composite facer maintains the continuous separating layer required. This will minimise the risk of interstitial condensation forming at the slab/insulation interface.
- Lay a proprietary underfloor heating system, generally comprising pipework in coils. Pipe retaining clips may be inserted directly into the Celotex insulation.
- Apply the screed over the Celotex insulation boards to a thickness recommended by the manufacturer of the underfloor heating system (normally 75mm).
- Compact the screed solidly when laid.
- Allow the screed to dry thoroughly before an impermeable surface, such as a vinyl floor finish, is applied. (Consult a specialist flooring contractor.) These recommendations are suitable for normal domestic floor loadings.
- If higher loadings are required it may be necessary to increase the screed thickness and provide reinforcement within the screed. Consult a structural engineer or specialist flooring contractor.
Installation guidelines for suspended timber floor applications
- Install joists in the conventional manner, with solid or diagonal strut bracing as necessary. (NB: diagonal bracing may lead to thermal bridging).
- Fix battens to the sides of the joists to support the insulation and to form a cavity for the underfloor heating, between the insulation and floor boards.
- Use the Celotex Insulation Saw to cut the Celotex FI5000 insulation to achieve a tight fit, then push the boards firmly down between the joists.
- Insulate the gaps between the joists and wall to prevent thermal bridging.
- Lay a proprietary underfloor heating system within the cavity, generally comprising pipework in coils, to the manufacturer’s guidelines.
- Install either chipboard or soft wood floor boarding directly onto the joists.