Flat Roof Insulation Between And Under Joists

A cold flat roof is one where the insulation is between or between and below the roof joists.

Flat roof insulation between and under joists.

The majority of domestic cold flat roofs use insulation between and under the joists. The full version allows any size. Alternatively battens can be secured to the underside of the. A cold flat roof is defined by insulation being installed between and if necessary underneath the timber joists.

As for insulating below the joists an insulating laminate insulation bonded to plasterboard such as celotex pl4000 or a separate rigid pir insulation board finished with a separate sheet of plasterboard can be securely fixed to the joists to provide an internal finish to the roof. Where insulation depth is restricted by the flat roof construction it may be necessary to install the roof insulation between and below the joists to create a cold deck structure. I ve built a timber frame to support a new plasterboard ceiling below the existing one. 1 enter joist details 1 1 span and joist spacing.

Flat roof with asphalt finish with felt boarding insulation. There is only a small gap between this ceiling and a concrete roof cold roof felt covered. A warm flat roof is defined by insulation being installed on top of the roof deck. It is preferred to have the bulk of the insulation between the.

The rule of thumb for foil faced boards like thermapitch tp10 or kooltherm k7 in this scenario is that you can have no more insulation under the joists than you have between the joists. This is used for refurbishment e g. I intend to fill between my joists with foil backed insulation board 75mm with a thin layer of insulation on top of the joists. Technical services online u value calculator.

Here the roof deck is maintained at the. If you put insulation under the decking and between the joists you lower the temperature of the decking and lower the due point thus bringing it closer to the danger point of being in the building. Energy assessments by celotex. Here the roof deck is maintained at the same temperature as the internal conditions hence warm deck roof.

Good question theoretically when building a warm roof the vaper control layer goes on the warm side of the insulation. Between and under joists. The insulation is below the deck but above the plasterboard. Flat roof joist calculator.

Between and over rafters. This demo version is fixed at 1m clear span.