Increasing Roof Rafter Depth For Insulation

For example if the existing joists are two by eights which are 7 5 inches deep you can add two by six boards which are 5 5 inches deep.

Increasing roof rafter depth for insulation.

Almost there with the old fo. It works well to increase the r value and furring strips and then drywall can be applied. 12 inches r38. Use cleats the same length as the width of the.

Rafters are 83mm deep x 63mm wide at 425mm centres. In any case you will not be able to use your present roofsystem. Each inch of batt type insulation provides an r value of 3 1 to 3 5 and loose insulation provides 2 9 to 3 7. Attach 1 2 inch wood cleats to both sides of the existing rafter.

6 inches r19. This gives you a total joist height of 13 inches which. Measure the depth of the existing insulation. Multiply the appropriate r value times.

After a bit more destruction and dust it is time to look at how we increased the rafter depth in preparation for the insulation. How to increase rafters for insulation step 1. Install a timber stop batten across the rafters as shown in position c with the batten equalling the thickness of the quinn therm insulation. For future reference here is the cavity depth you need for some common insulation r values.

Lay quinn therm qr insulation boards above the rafters butted tightly against the stop batten and supported on both sides by the rafters. For instance if the roof has 2 by 6 rafters and. You may want to consider applying a rigid polyisocyanurate insulation typically r7 to 8 per inch on the bottom of the rafters after installing baffles continuous from eave to peak and batt insulation between the rafters. I want to insulate with 50mm celotex or similar then plasterbd skim over.

Advised i need 50mm air gap for ventilation therefore need to increase depth of rafter by min. Figure the rafter depth needed to provide the desired r value. 3 5 inches r13.