Loft Insulation Between Roof Joists

You could even buy insulation and floor boards that are already bonded together which makes the job much faster and easier.

Loft insulation between roof joists.

This involves insulating between and over the wooden joists immediately above the ceiling of your top floor. If the loft is going to be used as living space then the insulation should be placed at rafter level to create a warm roof. Between and under joists. But if you simply fill the spaces between the joists with insulation and then board over the top you won t achieve an adequate depth of loft insulation.

Typically the gap between the joists is either 380mm or 570mm so you will need a width of insulation similar to this so it can fit snugly between the joists. A cold deck flat roof will typically require insulation to be installed between the roof joists to comply with building regulation requirements. Rolls of mineral wool can be used if the joists in your loft are regular. But if you plan to use your loft for storage only then a conventional cold roof option where the mineral wool insulation rolls are placed in between the ceiling joists above the top floor.

To increase the thickness of your roof insulation layer you can. Unless the joists are exceptionally deep there is also likely to be a requirement to install insulation to the underside of the joists as the upper 50mm of joist space is usually required to be left clear for ventilation purposes. Joists are the horizontal beams which make up the floor. The first layer of wool is placed between the joists and then a second layer is placed at right angles which covers the joists and also makes the insulation up to the correct depth of 270mm.