Flat Roof Insulation Above And Between Joists

Refurbishing an existing timber joisted flat roof which has no insulation.

Flat roof insulation above and between joists.

It is also suitable for retrofit with a substantial renovation of the roof. Set the quinn therm qrfr ply insulation boards onto a wide 30mm bead of vapour resistant sealant applied to the upper surface of all the joists and cross noggins. Flat roof detail masonry cavity wall flat roof insulation above and between joists. Flat roof detail examples.

The insulation is below the deck but above the plasterboard. By majority the rule of thumb is that in a domestic house not flats approximately a third of the total thermal performance of insulation can be placed below the deck with two thirds above. Flat roof detail masonry cavity wall flat roof insulation above and between joists. This method of insulation can also be used to upgrade the thermal performance of an existing roof without affecting the waterproofing system.

Bs 5250 2011 the british standard for the control of condensation in buildings does not recommend installing insulation between timber joists as well as above the deck. The roof itself is therefore kept warm. The following images provide examples of flat roof details. A cold flat roof is defined by insulation being installed between and if necessary underneath the timber joists.

Good question theoretically when building a warm roof the vaper control layer goes on the warm side of the insulation. Warm deck insulation 1. Here the roof deck is maintained at the. A warm flat roof is defined by insulation being installed on top of the roof deck.

The loft space can be used as a habitable room. 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. This is used for refurbishment e g. Parapet detail masonry cavity wall flat roof with parapet insulation.

An over and between rafter insulation solution can be a feature of a new build project. How to install insulation in a flat roof with timber deck insulated above the joists. Celotex polyisocyanurate pir foam insulation boards are easy to cut and handle. A warm roof is defined as being when the all or the majority of the insulation is above the joists or deck.

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. 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.