Flat Roof Insulation Between And Over Joists

The vapour control layer is above the decking but below the insulation.

Flat roof insulation between and over joists.

This method of insulation can also be used to upgrade the thermal performance of an existing roof without affecting the waterproofing system. Flat roof insulation between and under joists a cold deck flat roof will typically require insulation to be installed between the roof joists to comply with building regulation requirements. The majority of domestic cold flat roofs use insulation between and under the joists. To increase the thickness of your roof insulation layer you can.

You could even buy insulation and floor boards that are already bonded together which makes the job much faster and easier. To protect the roof from the potential of condensation occurring unseen within the construction it s important to remember that the layer of insulation installed over the rafters should as general rule be double the thickness of the insulation layer between the rafters. Learn more about warm roof cold roof construction. 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.

The insulation is immediately below the waterproofing layer. 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. Can insulation be placed between and over flat roof joists. If insulation is placed on top of the flat roof joists and as such the joists are not fastened to the boarding above the depth to breadth ratio of the joists should not exceed a ratio of 4 to 1.

Lay mineral wool between the joists and then fit rigid insulation boards across the joists with floorboards on top. 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.