Complete Guide for Home Made Roof Trusses Pro Barn Plans

Complete Guide for Home Made Roof Trusses Pro Barn Plans

Learn how to build your own roof trusses with lumber for a variety of applications. Perfect for clear spans over 20. Framing applications and step by step instructions.

Knowing when and where to use home made roof trusses is of absolute importance. The basic rule of thumb is that home made roof trusses are generally frowned upon by building inspectors. If you are building a project that requires a building permit, then you will not be able to build your own roof trusses unless you are an engineer. Roof trusses are also more trouble than they are worth for anything with a span of less than 20. It is simply easier to stick frame most applications. For buildings like pole barns, workshops, and pavilions that need to remain open in the center there is no better way to do it than with a wooden truss.

Understanding How Roof Trusses Work

The biggest load on aroof truss is in the center; just like it is with most anything else. The rafters meet in the center and have a post or webs directly beneath them. The post transfers the loads from the rest of the web braces to the center apex. The center can not drop without the bottom spreading. The bottom can not spread because it has a chord that spans the width of the truss. This simple design has amazing strength.

Most commercially built trusses use No. 1 pine attached together with metal plates called gang nails. For our purposes we will use No. 2 pine attached together with plywood gussets. Make the gussets from at least 5/8 laminated plywood. 8 x 8 squares work well for joints involving one web. For joints with more than on web make the gussets at least four inches larger for each addition framing member. Use a gusset on both side of the truss at each joint (all joints will be at web intersections). Nail them on with 8d coated nails. These gussets make for very strong connections. but they do not offer much support if the truss is being maneuvered on its side. Too much bending and they will fail.

Building the Trusses Step by Step

Select as smooth and flat a place as possible. A concrete workshop floor is ideal. They can also be built on the ground; just be ready to use live strings instead of popping chalk lines. Pop a chalk line using a non-permanent color such as blue. The line should be at least as long as the span. Mark the ends of the span with a pencil. From these marks, square up a line on each end to four inches. These are known as the plumb cuts for reference. Use a rafter calculator such as the one at BlockLayer.com  to find the length of the rafter. Find the center of the span and mark it on the bottom chord. Mark the rafters by marking two small arcs on the floor measuring the length of the calculated  rafter from the plumb cuts you squared up four inches from the ends of the span.Pop a line from the intersection of the two arcs (the apex) to the center point on the bottom chord. Check this to make sure it is square. Pop lines from the apex to the plumb cuts on each end. Check the angles of the rafters to make sure they are on the proper pitch. The layout should look like the shape of a roof at this point.

Pop an offset line from the bottom line 3 1/2 up. Pop lines from the rafter lines 3 1/2 down. Now is a good time to extend them for the overhangs. The layout of the truss should follow this diagram. It will keep all spans below 10 feet for any span below 30.  For spans greater than this, additional web braces are needed. Just remember, that the longer the span, the more force will be at work on the truss.

This is the most effective layout for most spans up to 30.

Build the first truss to the layout on the floor. Just tack the members together. Make sure all joints occur at a web intersection. Label the parts and use them as patterns. Build one truss at a time by nailing on the gussets with the truss laying right in the layout. Flip the truss over or stand it up to nail the gussets on the other side. Repeat this process until the trusses are finished. Stack them flat if you are not going to use them right away.

Setting and Bracing the Trusses

The first truss is the toughest one. It must be firmly braced in a plumb position no matter what it takes. Long 2 x 4s nailed together to a length of about 22 work well when nailed close to the top of the truss and down to a solid stake in the ground. For applications requiring longer braces, consider guy lines. Tie the trusses together with blocks nailed up as high as possible. Two feet center trusses require 25 1/2 blocks to face nail them. Once about six trusses have been set, permanently brace them for safety. Collapses while setting trusses are always catastrophic and they can even be deadly. Take your time and make sure you know what you are doing before even attempting to set your own trusses. Experienced help and a boom truck will make the job go much smoother.

Trusses themselves have no lateral strength. This why bracing is critical. These braces keep the trusses from bending laterally. The decking or roof battens keep the top chords from bending so there is no need for lateral braces for the top chords. The bottom chords on most applications will have a web intersection about every 10 feet apart; this makes for an ideal place for the lateral braces to run. For example, a truss with thirty feet span will have a bottom chord thirty feet long. Ideally, the chord will be divided into three equal sections of ten feet by two web braces that go to the apex at the ridge. This makes for a good place to have the lateral brace. Two runs of 2 x 4s on the bottom chord will keep the trusses straight and help maximize their strength. On our particular model, the spans  are closer to eight feet and we have an additional web intersection. This design will have three rows of braces.

Closing Thoughts on Wooden Trusses

Trusses are simply the best way to build most roofs. They will maintain their integrity for the life of the building. Just remember that their are dangers inherited with the installation process. Dont forget to use high quality materials and experienced workers and your truss building project will not be so bad!

Learn how to build your own roof trusses with lumber for a variety of applications. Perfect for clear spans over 20. Framing applications and step by step instructions.

Knowing when and where to use home made roof trusses is of absolute importance. The basic rule of thumb is that home made roof trusses are generally frowned upon by building inspectors. If you are building a project that requires a building permit, then you will not be able to build your own roof trusses unless you are an engineer. Roof trusses are also more trouble than they are worth for anything with a span of less than 20. It is simply easier to stick frame most applications. For buildings like pole barns, workshops, and pavilions that need to remain open in the center there is no better way to do it than with a wooden truss.

Understanding How Roof Trusses Work

The biggest load on aroof truss is in the center; just like it is with most anything else. The rafters meet in the center and have a post or webs directly beneath them. The post transfers the loads from the rest of the web braces to the center apex. The center can not drop without the bottom spreading. The bottom can not spread because it has a chord that spans the width of the truss. This simple design has amazing strength.

Most commercially built trusses use No. 1 pine attached together with metal plates called gang nails. For our purposes we will use No. 2 pine attached together with plywood gussets. Make the gussets from at least 5/8 laminated plywood. 8 x 8 squares work well for joints involving one web. For joints with more than on web make the gussets at least four inches larger for each addition framing member. Use a gusset on both side of the truss at each joint (all joints will be at web intersections). Nail them on with 8d coated nails. These gussets make for very strong connections. but they do not offer much support if the truss is being maneuvered on its side. Too much bending and they will fail.

Building the Trusses Step by Step

Select as smooth and flat a place as possible. A concrete workshop floor is ideal. They can also be built on the ground; just be ready to use live strings instead of popping chalk lines. Pop a chalk line using a non-permanent color such as blue. The line should be at least as long as the span. Mark the ends of the span with a pencil. From these marks, square up a line on each end to four inches. These are known as the plumb cuts for reference. Use a rafter calculator such as the one at BlockLayer.com  to find the length of the rafter. Find the center of the span and mark it on the bottom chord. Mark the rafters by marking two small arcs on the floor measuring the length of the calculated  rafter from the plumb cuts you squared up four inches from the ends of the span.Pop a line from the intersection of the two arcs (the apex) to the center point on the bottom chord. Check this to make sure it is square. Pop lines from the apex to the plumb cuts on each end. Check the angles of the rafters to make sure they are on the proper pitch. The layout should look like the shape of a roof at this point.

Pop an offset line from the bottom line 3 1/2 up. Pop lines from the rafter lines 3 1/2 down. Now is a good time to extend them for the overhangs. The layout of the truss should follow this diagram. It will keep all spans below 10 feet for any span below 30.  For spans greater than this, additional web braces are needed. Just remember, that the longer the span, the more force will be at work on the truss.

This is the most effective layout for most spans up to 30.

Build the first truss to the layout on the floor. Just tack the members together. Make sure all joints occur at a web intersection. Label the parts and use them as patterns. Build one truss at a time by nailing on the gussets with the truss laying right in the layout. Flip the truss over or stand it up to nail the gussets on the other side. Repeat this process until the trusses are finished. Stack them flat if you are not going to use them right away.

Setting and Bracing the Trusses

The first truss is the toughest one. It must be firmly braced in a plumb position no matter what it takes. Long 2 x 4s nailed together to a length of about 22 work well when nailed close to the top of the truss and down to a solid stake in the ground. For applications requiring longer braces, consider guy lines. Tie the trusses together with blocks nailed up as high as possible. Two feet center trusses require 25 1/2 blocks to face nail them. Once about six trusses have been set, permanently brace them for safety. Collapses while setting trusses are always catastrophic and they can even be deadly. Take your time and make sure you know what you are doing before even attempting to set your own trusses. Experienced help and a boom truck will make the job go much smoother.

Trusses themselves have no lateral strength. This why bracing is critical. These braces keep the trusses from bending laterally. The decking or roof battens keep the top chords from bending so there is no need for lateral braces for the top chords. The bottom chords on most applications will have a web intersection about every 10 feet apart; this makes for an ideal place for the lateral braces to run. For example, a truss with thirty feet span will have a bottom chord thirty feet long. Ideally, the chord will be divided into three equal sections of ten feet by two web braces that go to the apex at the ridge. This makes for a good place to have the lateral brace. Two runs of 2 x 4s on the bottom chord will keep the trusses straight and help maximize their strength. On our particular model, the spans  are closer to eight feet and we have an additional web intersection. This design will have three rows of braces.

Closing Thoughts on Wooden Trusses

Trusses are simply the best way to build most roofs. They will maintain their integrity for the life of the building. Just remember that their are dangers inherited with the installation process. Dont forget to use high quality materials and experienced workers and your truss building project will not be so bad!


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