Quick answer: PIR insulation is not generally banned in Wales. The rules depend on the building type, height, where the insulation sits in the construction and the fire classification required for that project.
PIR is still widely used in suitable roof, wall and floor build-ups. Where a project has a defined fire requirement, use the exact product and tested construction specified for the job rather than assuming all PIR boards have the same fire performance.
PIR insulation is not banned for normal building use
Welsh Building Regulations do not impose a blanket ban on PIR insulation. The main restrictions apply to combustible materials in certain external-wall applications and taller residential buildings.
That is different from saying PIR cannot be used in roofs, floors, internal walls or other suitable constructions.
External-wall rules are stricter on taller buildings
Wales introduced restrictions on combustible materials in the external walls of certain buildings over 18m, and the rules were tightened again from 20 December 2025 to set additional limits on certain combustible products in residential buildings with a storey between 11m and 18m.
For current requirements, refer to Approved Document B for Wales and the current Welsh Building Regulations guidance for the project.
PIR does not have one universal fire rating
Reaction-to-fire performance belongs to the exact product, including its formulation and facings. Do not assume a generic fire classification from the words “PIR insulation”.
Wern-Wood sells PIR by specification rather than brand, and the manufacturer supplied can vary. Where a fire classification is required, use the technical data or Declaration of Performance for the actual board being installed.
Fire performance belongs to the complete construction
A wall, roof or floor is assessed as a complete build-up. Plasterboard, cavities, membranes, framing, insulation and other layers can all form part of the required fire performance.
Do not create a fire-rated construction by combining individual products that each mention fire performance. Follow the tested or specified system for the project.
Can PIR be used in a normal house?
Yes, PIR can be used in suitable domestic roof, wall and floor constructions where the product and complete build-up meet the relevant requirements.
If the project has a specific fire requirement, building-control condition or external-wall restriction, check that requirement before choosing the insulation.
Shop PIR insulation
For standard thermal-insulation projects, browse our PIR insulation range or shop rigid PIR insulation board.
For a comparison with mineral wool, read PIR vs Mineral Wool Insulation.
