When using insulation boards, how are these fixed to the subfloor?

The way the insulation boards are fixed to the subfloor depends on the base type.

On a concrete base, the insulation boards are put down with a suitable flexible tile adhesive. The boards should be laid with staggered joints and once the flexible tile adhesive hardens, the joints should be reinforced with glass fibre tape.

On a wooden subfloor, the insulation boards should be put down with a suitable flexible tile adhesive and as with concrete subfloors, the insulation boards should have staggered joints.

When the adhesive has set, but not necessarily dried completely, the boards should be fixed using wood screws and washers. The insulation boards should be screwed down at 200mm centres, the screw washer fixing needs to be tightened into the board until the screw head is flush with the surface. After, the joints should be reinforced with glass fibre tape.

For more information on installing insulation boards and why you should do it, read our handy guide.