Insulation

Rockwool over the top of insulation board?

Philip Semple 17/12/2025 - 7.57 AM

To save time I've had a builder come in to put 50mm insulation boards under the subfloor. They've used 2 x 25mm boards to make up the thickness but they do not sit flush with the top of the joists. Even though the insulation benefits will be negligible I was thinking of topping up the gaps with rockwool to sit flush with the underside of the floorboards. The insulation boards are wedged tight so it would be hard to raise them higher. After that the laminate will go onto with a vapour barrier underlay. Does that seem acceptable? Thanks

PDH Insulations Ltd

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St Helens

It’s an option Phillip but really you would be better with the haRd board insulation being flush with your floorboards as they are a better product Pdh

Answered17 December 2025

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