Quick answer: for most PIR insulation boards, use a fine-toothed or specialist insulation saw for thicker boards. Thinner PIR can also be scored with a sharp knife, snapped over a straight edge and the facing cut through on the reverse.
Accurate cuts matter because PIR performs best when boards fit neatly together with minimal gaps. If you are cutting boards for a project, shop our PIR insulation board in 25mm, 50mm, 75mm, 100mm and 150mm thicknesses.
Use a fine-toothed saw for thicker PIR boards
A fine-toothed hand saw or specialist insulation saw is the straightforward option for thicker PIR board. Mark the cut clearly, support the board on a flat surface and keep the saw square to the face so the cut does not wander.
Industry guidance identifies a fine-toothed saw as the most common method for PIR, particularly on thicker insulation.
Thin PIR can be scored and snapped with a sharp knife
On thinner boards, a sharp utility knife can be used to score the facing and foam along a straight edge. The board can then be snapped over a straight edge before cutting through the facing on the reverse.
This method avoids sawing through the whole board, but it becomes less practical as the insulation gets thicker.
Use a straight edge to keep cuts accurate
Mark both ends of the cut and use a long straight edge as a guide. PIR is easy to cut, but a saw blade can drift through the thickness even when the line on the top face looks correct.
For boards being fitted between timbers or butted together, check the cut edge before installation and trim it if necessary rather than forcing a poor fit.
Cut PIR in a ventilated area and protect your eyes and lungs
Cutting or drilling PIR insulation can release dust. Work in a ventilated area and use suitable eye protection and a dust mask when cutting boards.
A knife-and-snap method can produce less loose material than sawing, but the correct method still depends on the thickness and the cut you need to make.
Choose the cutting method to suit the board thickness
- Thinner PIR: a sharp knife and straight edge can work well for straight score-and-snap cuts.
- Thicker PIR: use a fine-toothed hand saw or specialist insulation saw.
- Detailed or awkward cuts: mark carefully and use the tool that lets you keep the cut controlled and square.
Shop PIR insulation board
Our PIR insulation range includes rigid insulation board and PIR insulated plasterboard. For standalone rigid boards, shop 25mm, 50mm, 75mm, 100mm and 150mm PIR insulation board.
If you are still deciding whether PIR is the right material, read What Is PIR Insulation?.
