When considering insulating a floor the following guide gives you some insight in to the best methods and materials to use for each area.

Suspended floors

The UdiFLEX wood fibre wool product is the best, all round insulation for this job as it is easy to cut and fits snugly between even the most wonky joists.

Initially we recommend either battening underneath the joists (running perpendicular to the joists) at 600mm centres or, if that isn’t possible, draping the UdiSTEAM Tex 155 breather membrane between the joists to support the UdiFLEX batts.

The joints in the UdiSTEAM Tex 155 membrane don’t need to be taped unless you have significant airflow beneath the floor. If so, use the UdiSTEAM Tex tape.

When calculating the amount of UdiSTEAM membrane allow to come up both sides of each joist as well as along the top and between each joists. E.g If you have 21 joists at 150mm x 45mm and they are at 400mm centres you’d need 21 x (0.150 + 0.150 + 0.045 + 0.355)m or 14.7m per run.

The UdiFLEX wood fibre batts are pressed snugly between the joists. When calculating the amount required, don’t forget to remove the volume of timber in the floor. E.g. Using the above example, although the floor is 8m wide, you only need (8 - (21 x 0.045))m or 7.055m once the joist area is removed.

When considering insulating a suspended floor it is as important to consider moisture flow and air tightness as it is in a wall or roof. With this in mind you need to use the UdiSTEAM 10 plus variable VCL membrane to make the structure air tight and to prevent any condensation formation. Ensure all the joints and edges are taped with UdiSTEAM Elastoflex tape.

The floor is then ready to receive floor boards, chipboard or an engineered floor finish.

Solid Floors

For solid floors, UdiTHERM wood fibre boards are laid to the required depth over a concrete slab and DPC, staggering joints between the layers. We recommend using the UdiSTEAM 10 plus variable VCL membrane over this, for airtightness and to prevent condensation, as above. Once installed you can lay your floating timber floor or a dry screed system, such as Lithotherm underfloor heating tiles.

If you have any questions or if your floor structure is not covered here, please contact us.

 

Thermal and acoustic flexible wood fibre wool insulation - UdiFLEX - Back to Earth
Thermal and acoustic flexible wood fibre wool insulation - UdiFLEX from £23.28
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Square edge wood fibre insulation boards - UdiTHERM SK - backtoearthsupplies
Square edge wood fibre insulation boards - UdiTHERM SK from £3.53
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High density wood fibre underlay board (8mm) - UdiSTEP - Back to Earth
High density wood fibre underlay board (8mm) - UdiSTEP from £2.06
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Variable vapour control layer and airtightness membrane - UdiSTEAM 10 plus - backtoearthsupplies
Variable vapour control layer and airtightness membrane - UdiSTEAM 10 plus £165.08
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Breathable roofing underlay - UdiSTEAM Tex 155 - backtoearthsupplies
Breathable roofing underlay - UdiSTEAM Tex 155 £126.75
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Air tightness tape for membranes (60mm) - UdiSTEAM Tex - backtoearthsupplies
Air tightness tape for membranes (60mm) - UdiSTEAM Tex from £16.45
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Flexible air tightness tape - UdiSTEAM Elastoflex - backtoearthsupplies
Flexible air tightness tape - UdiSTEAM Elastoflex from £15.83
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