Increasing Roof Rafter Depth For Insulation

Figure the rafter depth needed to provide the desired r value.

Increasing roof rafter depth for insulation.

For future reference here is the cavity depth you need for some common insulation r values. Use cleats the same length as the width of the. Advised i need 50mm air gap for ventilation therefore need to increase depth of rafter by min. It works well to increase the r value and furring strips and then drywall can be applied.

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. Almost there with the old fo. I want to insulate with 50mm celotex or similar then plasterbd skim over. 3 5 inches r13.

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. 9 inches r30. Multiply the appropriate r value times. 6 inches r19.

Rafters are 83mm deep x 63mm wide at 425mm centres. 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. 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. Install a timber stop batten across the rafters as shown in position c with the batten equalling the thickness of the quinn therm insulation.

Attach 1 2 inch wood cleats to both sides of the existing rafter. 12 inches r38. So we extended our rafters with some two by fours giving us the space to increase our ceiling insulation to r30. How to increase rafters for insulation step 1.

For instance if the roof has 2 by 6 rafters and. In any case you will not be able to use your present roofsystem. This gives you a total joist height of 13 inches which.