Warm Flat Roof Insulation Between Joists

This demo version is fixed at 1m clear span.

Warm flat roof insulation between joists.

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. The full version allows any size. In a warm flat roof additional insulation should not be used between the roof joists. Alternatively battens can be secured to the underside of the joists and gmw fitted between these in much the same way as between the main roof joists.

Whether you re looking to insulate at joist level for a cold roof where joist depth can be an issue or above the roof deck where overall roof height may need to be considered if a warm roof construction is desired. Insulation is placed in between the joists underneath the roof surface above. Both these variants require different approaches to insulation which will be covered in this guide. Flat roof with asphalt finish with felt boarding insulation.

The vapour control layer is above the decking but below the insulation. Good question theoretically when building a warm roof the vaper control layer goes on the warm side of the insulation. 1 enter joist details 1 1 span and joist spacing. Probably ok in a limited area but keep to minimum above the wall head to improve sound insulation.

Cold deck roof a cold deck roof is where the insulation is placed between the joists rafters or in between the ceiling joists in the case of a pitch roof. The insulation can be adhered mechanically fixed or loose laid. The underside of the rafters in this case will need to be finished with a suitable vapour control layer vcl and plasterboard to provide a suitable internal finish to the roof. For this reason i would prefer to have insulation between the joists as with a cold flat roof construction.

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 joist calculator. Flat roof insulation. No ventilation is required for these types of roofs.

But as we are pushing head height our dormer meets the roof ridge right at ridge level so any vents and building regs seem to require a lot of them will be a little too exposed in my opinion. In a warm pitched roof it is acceptable to put a limited amount of insulation between the rafters depends on thermal resistance of this layer. How to install insulation in a flat roof with timber deck insulated above the joists. A warm deck roof is where the insulation is placed on top of the rafters joists and the roof covering is then placed over the insulation.

Warm deck insulation 1.