Insulating between rafters for loft conversion

When a loft conversion is planned, choosing the right materials is key to the achievement of a high standard. Use our Ballytherm Loft insulation mini guide for Insulating between rafters for loft conversion.
The properties of Ballytherm insulation boards make them more than suitable to get to it:

  • • Lowest thermal conductivity
  • • Highest strength for the rafters to span
  • • Set in two layers, their reflective surface reduces heat loss
  • • Excellent thermal behavior of roofs

Ballytherm Loft insulation mini guide

Preparing the support

  • •Leave an air space of at least 20 mm between the support and insulation
  • •Make sure the rafters appropriate sections
  • •Fix the battens vertically on the floorboards using screws or nails and aligned with the rafters if possible
  • •Set a horizontal batten at the lower part of the roof skirt
  • •The overlap of the sections must always be provided on a batten
  • •Foresee a bar joist or intermediate batten if necessary (when the overlap falls between two battens)
  • • When a rafter shows an unfitted depth, this can be solved by fixing a lath or batten underneath the sides of the rafter

Extension of insulation 

  • • The extension of the insulation will be performed vertically
  • • Staple the insulation on battens. Always respect the basic rules of placement
  • • Ensure continuity of the insulation at the ridge and at meetings with the vertical surfaces


  • • Set counter battens vertically and aligned with the first ones and nailed or screwed to them through the insulation
  • • Then set the horizontal battens. The distance between axes will fit the type of roof cover appropriately
  • •Set the roof
  • • It is strongly recommended that an air chamber of about 50mm min. is left between the tile and insulation for the roof rafters
  • • Ensure this chamber (on meeting ridges, ridge ends or eaves) gets proper ventilation
  • • Placing a finish should be performed by qualified personnel and in accordance with the current standards and specifications by the manufacturers

More detailed information:
Insulating Above And Between The Rafters
Insulating Between And Below The Rafters
Insulating Loft Conversions

To find out more about loft conversions and insulation contact our team at for more information.

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