Strong Flat Roof Rafters

To cut roof rafters start by fixing the stair gauges on your framing square to the dimensions of your pitch.

Strong flat roof rafters.

Spacing your 2 4 shed rafters at 24 on center limits the width of your roof. As a general rule roofs that have a high human occupancy rate should be framed with rafters every 16 structures such as sheds or barns can be frames with rafters every 24 again make sure to consult local codes. For heavy loads 2x4s can span up to 5. Long ago engineers learned they could add greatly to the strength of a roof by inserting compression members within the frames.

For light load roofs 24 o c. Live load is weight of furniture wind snow and more. Measure the thickness width and length of the rafters in your home and purchase one piece of framing lumber of the same size for every two rafters in your attic. 1 ft 0 3048 m.

But the rafters must resist bending flexion where they are relatively weaker. Most roof framing is 24 on center and you can still build sheds up to 14 with 2 4 rafters at 24 on center. As the load goes up for snow in northern climates or for heavy roofing material like tile the span length decreases. Corbett grace their parents and even their kids are learning a lot about the many ways a few right many wrong to build a high performance home.

Once you ve marked the lines use your pencil to draw the diagonal length on the rafter. Next set the framing square on top of the rafter beam and use a pencil to trace the outside edge of the framing square s tongue. 2 are indicated below. Measure and cut each piece of framing lumber into two boards measuring one third and two thirds the length of your rafters.

According to the american wood council the maximum span for rafters is about 30 feet and that s with a relatively low load of 20lbs per square foot. 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. Live load 20 lbs ft 2 956 n m 2. 2 4 rafters can span up to 7.

Dead load weight of structure and fixed loads 15 lbs ft 2. These dimensions take into account a snow load of 9 07 kilogram per square foot psf. 1 psf lb f ft 2 47 88 n m 2. 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.

Such trusses are not hard to make. So the rafters must be made of two by sixes two by eights or even bigger stock. Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no. If your project had a rafter length of 8 or less a safe and strong method is to use 2x8 framed 16 on center.