R30 Roof Rafters

Rafter span tables use these tables to determine lengths sizes and spacing of rafters based on a variety of factors such as species load grade spacing and pitch.

R30 roof rafters.

Here s how to use 3 layers of 2 inch polyiso foam board to meet code and keep your ne. Owens corning r 30 ecotouch pink cathedral ceiling kraft faced fiberglass insulation batt 23 3 4 in. Visit the roof framing page for more information on cutting roof rafters and visit the roof pitch calculator for determining rafter lengths based on rise and run. I 39 m stapling the bats between two 2x8 rafters and the attic roof.

If you re using fiberglass insulation you need thicker wall or ceiling cavities to fit insulation with a higher r value. Better than spray foam thermal break and relatively consistent r 30. R30c and r38c are available in both kraft faced and unfaced. And owens corning ecotouch high density insulation products are designed specifically for these rafters.

If insulation is allowed to bunch against the inside slope of the roof between the rafters air will be blocked before it can traverse the attic. For instance if the roof has 2 by 6 rafters and you want r 30 insulation which is standard in many communities you can add a 2 by 4 which will give you an 9 inch rafter space. By installing high density 8 inch fiberglass batt insulation the rafters will then meet an r 30 roof insulation standard. If you re framing a gable roof on a new house or building a shed or even a doghouse with a gable roof you ll need to cut a number of roof rafters.

R30 needs 9 inches. 39 installing r30 bat insulation 2x8 rafters compress insulation fit. The rafters in cathedral ceilings are usually made of 2 in. Before you cut your boards you ll need to measure the width of your building and calculate the exact length of each rafter.