Roof Insulation For 2x4 Rafters

We just had rebuilt repaired the roof of a flat roofed addition to our house due to a roof leak and resulting breakdown and mold problems.

Roof insulation for 2x4 rafters.

If your local building authority has a rafter spacing code you may not space rafters wider than required by code. 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. So at 16 oc each joist is 2 2x4s together. There are some unfinished crawl space areas in the corners on the upper floor.

A drywall sheet is 32 sqft. It s easy to say oh yeah just put 1 2 drywall on your ceiling forgetting that it weighs over 50 pounds. Moving to 16 on center you could span your spf 2x4s up to 6 for heavy loads and 9 for light loads which would still work with a 12 12 gable shed. Install a timber stop batten across the rafters as shown in position c with the batten equalling the thickness of the quinn therm insulation.

Whether there is a real hazard or not depends primarily on your local climate climate zone as well as your shingle color type and shading factors. 2 4 rafters can span up to 7. For light load roofs 24 o c. There is no standard spacing it depends on what size of rafters you want to use and the span of your shed.

Shaded or north facing roof pitches would be the most susceptible but with only 2x4 rafters and likely r13 or less the roof deck runs warmer drier than if it were insulated to current code min. Typical rafter spacing codes will specify a minimum spacing of 16 inches 19 2 inches or 24 inches. They are directly below the roof sheathing and are were insulated with fiberglass batts stapled between the 2x4 rafters. It s already a low ceiling 78 ceiling on the low side and 87 ceiling on the high side.

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. Lay quinn therm qr insulation boards above the rafters butted tightly against the stop batten and supported on both sides by the rafters. Spacing your 2 4 shed rafters at 24 on center limits the width of your roof. The rebuild was done the same way.

Let s say you ve 384 sqft of ceiling to cover. Rafters must be strong enough to hold the roof sheathing and the shingles. If your rafters are only 2x4 either you ve got about 400 sqft or you ve reinforcement load bearing partitions beams somewhere. For standard shed roof rafter spacing see rafter span chart.