Increasing Roof Rafter Depth For Insulation

Rafters are 83mm deep x 63mm wide at 425mm centres.

Increasing roof rafter depth for insulation.

12 inches r38. It works well to increase the r value and furring strips and then drywall can be applied. I want to insulate with 50mm celotex or similar then plasterbd skim over. 6 inches r19.

Lay quinn therm qr insulation boards above the rafters butted tightly against the stop batten and supported on both sides by the rafters. Attach 1 2 inch wood cleats to both sides of the existing rafter. 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. 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.

How to increase rafters for insulation step 1. For instance if the roof has 2 by 6 rafters and. Use cleats the same length as the width of the. 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.

Almost there with the old fo. This gives you a total joist height of 13 inches which. After a bit more destruction and dust it is time to look at how we increased the rafter depth in preparation for the insulation. Figure the rafter depth needed to provide the desired r value.

So we extended our rafters with some two by fours giving us the space to increase our ceiling insulation to r30. 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. Measure the depth of the existing insulation. In any case you will not be able to use your present roofsystem.

9 inches r30. 3 5 inches r13. Multiply the appropriate r value times.