Roof Rafter Support

Continuing on from part 3.

Roof rafter support.

Rafter ties resist the forces caused by gravity loads that would otherwise cause the roof to pancake and push out the sidewalls. Simpson strong tie offers a diverse line of hangers to handle almost any application with top flange concealed flange and field skewable and slopeable options. Rafter ties are required by code unless the house is designed so that the walls or a structural ridge beam carries the full load of the roof. By upper third here we mean one third of the length of the rafter from ridge to top plate.

Usually trusses are put 24 inches apart. Let s consider a basic gable wood roof framing design. In large buildings where heavy trusses are used the purlins are continuous members that rest. As each truss is put up on top of opposite walls it must be put up straight and supported while the next truss is put up.

Floor beam span tables of residential structural design we will now look at roof rafter and beam design. Use this table to determine the maximum lengths of ceiling joists based on species of lumber joist spacing and joist size. Before you cut your boards you ll need to measure the width of your building and calculate the exact length of each rafter. Joist hangers are designed to provide support underneath joist hangers are designed to provide support underneath the joist rafter or beam to provide a strong a connection.

In small roofs purlins are inserted between the rafters and nailed through the rafters. Purlins purlins are used in roof construction to support corrugated sheet metal if it is used or to support the sheathing of roofs framed with trusses. Here we have a wood framed gable roof. Ozco 56638 laredo sunset 2 inch hv rafter clip 10 per pack 4 8 out of 5 stars 27 mitek usp structural connectors jl26 face mount joist hanger light capacity 20 gauge g90 galvanizing finish steel 2 x 6 joist dimensional hangers 50 count.

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. A collar tie is a horizontal roof rafter compression connector that is located in the uppermost third of the span of a pair of opposed sloped or gable roof rafters. 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. To hold them up until the decking of the roof is placed on top a 12 foot 1 inch by 4 inch piece of lumber is used.

Rafter spans can be extended slightly beyond what the rafter tables suggest when there is a cantelever extending beyond the supporting wall. 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.