Started by KJones, August 31, 2019, 12:52:58 PM
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Quote from: Reninco on February 25, 2021, 11:43:49 AMThanks for posting the spec sheet.In truss manufacture there are some got-ya's that some designers use as to make the bid "more competitive" as Don_P was referring to. In your case no worries but for the rest of the readers I'll mention the things that one should look for or might be of interest.
Quote from: Don_P on February 27, 2021, 10:19:43 PMReninco, thank you, good explanations.KJones, It looks like .79" horizontal deflection. That means it is possible for the truss to push a long, unreinforced wall out of plumb that amount. To me that is excessive but it is a judgement call. If the truss is resting on a floor then that would be tying the walls together and no worries, if it is over something like a open greatroom I'd try to reduce that horizontal deflection.
Quote from: Reninco on February 28, 2021, 09:06:23 AMI agree with Don_P, I would talk to the designer and mention this concern if you have long walls without any partitions. Also the design is based on peak values which may not be a concern in your location but its best to talk to the designer with this concern. KJones I like the finished look of this style of truss as it always gives more volume to a cabin or house. Your plan specs are about the same as the comments I made for Nate. All wind conditions for your region are considered as is Nates comments. Mechanical fastener is requested etc.
Quote from: Don_P on March 01, 2021, 09:07:42 AMThat horizontal deflection is a judgement call. If both walls are equally "floppy" I try to keep it under around 1/2". This is not a strength issue it is a serviceability problem with no clear cut answers.
Quote from: Nate R on March 01, 2021, 09:46:02 PMI assume you're doing a 10/12 interior slope to accommodate head height in a loft? Maybe drop it to 8/12 or 9/12 as suggested above, but increase the heel height to compensate? This may be a simple design change for the truss designer, and might not be expensive. If you look at my truss design (posted previously/above), they just add a "spreader" wedge between the bottom and top chords to increase the heel height another 3 1/2 inches.
Quote from: Don_P on March 01, 2021, 07:18:17 PMLowering the inside pitch will do the most, the cheapest...
Quote from: Reninco on March 01, 2021, 08:13:44 PMIt costs very little to change on paper and very much to fix after being built.
Quote from: Don_P on March 03, 2021, 07:18:15 PMIf the geometry is acceptable it is a better truss. If you need more headroom can you increase wall height a bit?Take a look at both printouts...Reactions are the same, both are bearing the same loadsNow look at the difference in the forces. By making the truss deeper the internal forces dropped dramatically. Enough that they are now able to use visually graded #2 SPF lumber vs high end machine stress graded much stronger wood in southern pine, and as you noted they dropped a size to boot. I'm seeing 3/8" horizontal deflection, looks fine to me.