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Monday, August 12, 2013

Notes Truss Design: Mixing scrap 1x4 and 2x4 material to make 18 foot wide trusses

Trusses are awesome for we "do-it-yourself" people!   What I love most about trusses is that I can use scraps of almost anything to build full sized structures ... all I need is a large quantity of scraps ... and time ... and nails.  My dad once joked about a garage that I built that I had more nails in it than wood ... and if you measured by cost, he was right.  The wood was free, but not the nails.

A YouTube viewer asked about building an 18 foot wide cover out of scrap 2x4 and 1x4 material.  This blog post is to document my thoughts on the subject for the benefit of all.

There are at least two handy ways to use 1x4 material in truss construction.  The 1st, of course you can double it up and use it same as you would 2x4 material, and the 2nd is to use it for reinforcing members that nail onto the outside of the 2x4 material.  Because a picture is worth a thousand words, please view the diagram below:

Click Truss Image to Enlarge
The ziz-zag shaped pieces are 1x4 material nailed onto the larger triangular truss halves which are made of 2x4 material.  The left half of the diagram above is exactly how I would build a truss to span 18 feet.   If the height in the middle of the truss is 3 foot, then each wing can be 9 feet and that will give a standard 4/12 pitch roof.  A 4/12 roof is comfortable to walk on even for metal roofing.   Of course you should select a steeper roof pitch if there is any chance of significant snow accumulations.

The right half of the diagram represents a more general design for wider spans.  To increase strength, nail 1x4 material to both the front and back of the truss.

It is also handy to use material of all the same thickness and then sandwich the joints with pads of scrap plywood:

Of course you could use 1x4 material in this way by doubling it up to match thickness with the 2x4 material.

1 comment:

  1. That was an awesome work James!
    You would be interested to see our work for our RTM home