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Carpentry & Joinery

Under wood board insulation with ply and insulation board

Anonymous user 14/03/2024 - 2.35 PM

Hi, I have very old drafty polished pine floorboards. I am considering lifting the floorboards and fitting rigid insulation board between the joists. I will then cover over with a thin ply as a second layer to stop any draft that may find its way through the insulation board before re-laying my floor boards for final sand/polished. I will ensure that the underfloor vents are not blocked so that I have a through flow of underfloor air but am still concerned about condensation. I would welcome some advice about this and if I should be laying a membrane. Thanks. Aaron.

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2 Answers

HD Design and Build

Rating: 5 out of 5

Herne Bay

No need to insulate between the joists just insulate over the top and tape the joints As long as there is airflow underneath it should not condensate

Answered17 February 2015

Dugey Property

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Andover

HI, you could do this it will insulate well and stop any drafts without raising the finished floor level (FFL) my much (the thickness of the Ply). Airflow underneath the floor is crucial to avoid moisture build up which can lead to range of damp issues.

Answered13 January 2019