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Roof Framing

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#1 Harlon Suttle

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Posted 21 March 2016 - 12:30 PM

How to add rafter bracing ....need to add a purlin on the bottom of the roof rafter and then a brace member from the purlin to an interior wall ?  Softplan Tech had never heard of this ?  Hmmm pretty common around here....


Thanks in advance for your thoughts



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#2 Steve Haarmann

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Posted 21 March 2016 - 06:09 PM

This is very common framing in my area also.

But it is not a "standard" that can be determined by a formula in SoftPlan.

The purlin locations may vary per the framer and the bracing members must run from the purlin to a bearing wall (which is not defined for SoftPlan).

These are typically framed in my area with 2x6 material. The purlins and braces might be double "L" 2x6's.

An arbitrary formula could be created that used the ridge length times a factor (possibly 2) and called "purlins"

And another arbitrary formula could be created using rafter length times a small factor (1 in 10)  called bracing.


I use the phrase "arbitrary" because they are not based on any "real" framing variables.

They are simply used to estimate extra materials for these framing functions.

#3 Tom Rogers

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Posted 22 March 2016 - 07:35 AM

I agree with Steve.  Also I have used purlins in my vocabulary but in some locations they call them "strong backs".  Either way it is a tough way to call it out or to add it to a material list or rendering automatically.  You have to determine the overall length of roof and the loads applied to it plus find where your load bearing walls are (as for Softplan interior wall you have to create or mark them as bearing in the definition).  And then of course you have to transfer it all the way down to the foundation.  I think an arbitrary formula, like Steve mentioned, can get you close

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#4 Derk Burgers

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Posted 13 February 2019 - 12:02 PM

Has anyone made any headway on this or do you figure them yourself? I'm using some downtime to try to get into Softlist(I'm currently doing all the estimating). I've come across a 2x4 "ribbon" on floor trusses, 2x6 strong backs in the floor trusses, and 2x4 lateral bracing in the rafters that I don't see a way to automatically estimate.

#5 Kevin Rabenaldt

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Posted 13 February 2019 - 05:03 PM

I searched for a way to draw them and came up with workarounds when I create my drawings from the joists plan and rafter plan.  SP calls purlins those members that cross the rafters on the top of the rafters but we too use purlins under the rafters and code calls for maximum rafter span of 12 feet to be braced underneath.  You can easily find this in many framing examples on the internet.  Strongbacks around here are what are used on top of the joists.  If your joist span is more than 8' (I think), a strongback is required.  You can create a symbol out of solids for these, but material formulas no.  But I don't use the material estimates anyway. I have to locate all purlins and bracing back to walls on my roof framing plan.   I did create some 2d symbols to aid in adding in cross sections but usually then require editing to get them properly drawn.

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