ⓘ We are closed from Thursday 28th September 12pm & will re-open Monday 2nd October.  All orders & enquiries will be processed & responded to on the Monday.






UKFR Inverse Logo.png

Celotex PIR Insulation Boards

Keep your home as warm and energy efficient as possible.

From the leading and reputable brand Celotex, our range of PIR insulation boards is designed with low-emissivity foil, offering the best thermal insulation solution. They will keep your home better insulated and can be easily installed on the roof, walls, floors, ceilings or anywhere else requiring proper insulation.

Browse our Celotex insulation range below and benefit from fast delivery from our UK branches.

Sizes and Board Type


Buy Celotex Insulation

Celotex is a high-performance polyisocyanurate insulation board offering excellent thermal insulation. With a low thermal conductivity of 0.022 W/m.K, it is an ideal choice to reduce energy bills and improve the energy efficiency of buildings.

Our range is simple and uncomplicated; with each sharing dimensions of 2400mm x 1200mm, only differing in thickness size.

Celotex TB4000 PIR Insulation Board thickness: 20mm, 25mm, 30mm, 40mm.

Celotex GA4000 PIR Insulation Board thickness: 50mm, 60mm, 70mm, 75mm, 80mm, 90mm, 100mm

Celotex XR4000 PIR Insulation Board thickness: 120mm, 150mm

Celotex XR4000 PIR Insulation Board Pallets thickness: 110mm, 120mm, 130mm, 140mm, 150mm, 165mm, 200mm

Please note this will depend on stock availability. If we currently do not have the thickness you seek in stock, please get in contact with us and a member of our team will be happy to assist.

Why should I use a Celotex PIR insulation board?

Celotex is a game-changing brand for insulation, providing many benefits whilst remaining relatively thin compared to other sources of insulation. Some of these benefits include:

  • Excellent Thermal Performance - thermal conductivity of 0.022W/m.K reduces required thickness for target U-value
  • High-Performance Facer - low emissivity foil facing improves achievable U-value in sealed cavity air spaces
  • Easy Installation - they are lightweight & rigid making them easy to cut down to size, transport, handle and fit.
  • Cost-saving - excellent thermal performance reduces your energy consumption
  • Certified - Celotex TB4000 has been assessed by the BBA as fit for use in defined roof, wall and floor applications if installed, used and maintained as set out in the certificate. It has also achieved a BRE Green Guide Rating of A.

Insulation boards are designed to retain heat within the structure of your home to ultimately keep you warmer when you need it most.

It is important to note that Celotex PIR insulation, alongside similar brands, has a fire-resistance rating of Euroclass F - meaning it will combust easily when reacting to a fire. If you require fire-resistant insulation, check out our A1 classified wool insulation which includes glass and mineral wool.

What are Celotex PIR insulation boards used for?

PIR insulation is suitable for a wide variety of building applications and construction projects including:

Pitched Roof

  • Between and Under Rafters
  • Loft Insulation
  • Between and Over Rafters
  • Between Rafters
  • Pitched Roof Sarking

Flat Roofs

  • Balconies and Terraces
  • Between and Under Joists

Internal Walls

  • Partition Walls
  • Cavity Walls
  • Basement Walls
  • Masonry Walls
  • Exterior Walls
  • Timber Frame Walls

Ground Floors

  • Block & Beam Floor
  • Concrete Slab Floor
  • Upgrading Concrete Slab Floors
  • Suspended Timber Floors

Trusted supplier

UK Flat Roofing is a proud and trusted UK supplier of PIR insulation boards, serving happy and returning customers across the country. With nationwide delivery from a variety of branches, you’ll receive fast delivery if you place your order before 12 pm. With over 35 years of experience, our team has seen it all and is knowledgeable in a wide range of flat roof systems.

If you need any help with your order or have a question about a project, get in touch with us today via Whatsapp or drop us an email at sales@ukflatroofing.com.





Celotex insulation boards are made from polyisocyanurate (PIR) foam and have a foil facing on each side. Created by combining polyisocyanurate resin with a blowing agent, it creates a chemical reaction, making the foam insulation. This foam is placed between two emissivity aluminium foil facings and can be cut down to size to suit a variety of building projects including roofs, walls, and underfloor heating.

All of the boards are the same PIR boards. The codes refer to the thicknesses.

  • TB4000 is 20mm to 40mm
  • GA4000 is 50mm to 100mm
  • XR4000 is 110mm to 200mm

The thickness of insulation required will depend on many factors including the U-value required, the size and shape of the building element, and the type of insulation being used. Many online calculators can help you determine the appropriate thickness for your project; alternatively, don’t hesitate to get in contact with us and we will be happy to assist.

Celotex insulation boards have a Euroclass rating of F, which is considered the worst rating in terms of combustibility. However, it’s important to note that poor Euroclass ratings do not mean the material is unsuitable for home use.

The rating simply means it will not stop the spread of fire, so using fire-resistant materials in conjunction with Celotex PIR insulation products is ideal.

Celotex is a great alternative to Kingspan PIR insulation products.

Yes! All insulation needs a vapour barrier which should be installed on the warm/internal side of the insulation.

R-value measures how resistant a material is to heat flow; the higher the R-value, the greater the thermal resistance of the material.

U-value measures the rate heat flows through a building element, such as a wall, floor, or roof; the lower the U-value, the more effective the building element is at preventing heat loss or gain.

Insulation boards are easy to cut down but must be done safely to avoid damage. When cutting to size, use a fine-toothed saw or sharp knife, snapping the board over a straight edge and cutting the facing on the other side.