Increasing Roof Rafter Depth For Insulation

After a bit more destruction and dust it is time to look at how we increased the rafter depth in preparation for the insulation.

Increasing roof rafter depth for insulation.

It works well to increase the r value and furring strips and then drywall can be applied. Multiply the appropriate r value times. 6 inches r19. So we extended our rafters with some two by fours giving us the space to increase our ceiling insulation to r30.

Advised i need 50mm air gap for ventilation therefore need to increase depth of rafter by min. Lay quinn therm qr insulation boards above the rafters butted tightly against the stop batten and supported on both sides by the rafters. 12 inches r38. 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.

In any case you will not be able to use your present roofsystem. This gives you a total joist height of 13 inches which. Install a timber stop batten across the rafters as shown in position c with the batten equalling the thickness of the quinn therm insulation. Figure the rafter depth needed to provide the desired r value.

Rafters are 83mm deep x 63mm wide at 425mm centres. 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. Use cleats the same length as the width of the. Increase the rafter depth with an i joist deep enough to accommodate appropriate insulation insulate to required r value probably r40 strap the roof for ventilation or go solid eps or spray.

For instance if the roof has 2 by 6 rafters and. Measure the depth of the existing insulation. How to increase rafters for insulation step 1. 9 inches r30.

Almost there with the old fo. For future reference here is the cavity depth you need for some common insulation r values. 3 5 inches r13.