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Floor Insulation

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 SteicoFlex flexible wood fibre insulation 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 Ampatop Aero breather membrane between the joists to support the SteicoFlex batts.

The joints in the Ampatop Aero membrane don’t need to be taped unless you have significant airflow beneath the floor. If so, use the Ampacoll INT air tightness tape.

When calculating the amount of Ampatop Aero 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 SteicoFlex 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 Ampatex Sinco VCL membrane to make the structure air tight and to prevent any condensation formation. Ensure all the joints and edges are taped with the Ampacoll XT tape if the surfaces are smooth or the Ampacoll BK 535 tape if on to masonry.

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

Solid Floors

For solid floors, UdiTHERM  or Beltermo Kombi square edge wood fibre boards are laid to the required depth over a concrete slab and DPC, staggering joints between the layers. We recommend using the Ampatex Sinco 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.

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