Replies

1. 
   stinger | Sep 11, 2005 05:26pm | #1

   I'm not a truss engineer, but I don't believe there is any such thing as a "standard" scissors truss.

   If you want an energy heel, simply specify your desired heel height (12 inches or more is considered "energy") to your truss supplier, and they will doodle away and configure your roof arrangement.

2. 
   Stuart | Sep 11, 2005 06:09pm | #2

   I did a google search on 'scissors truss energy heel' and found the website for the Maple Valley Truss company in Michigan.  These pictures are from their website; I suppose there are probably other truss versions that accomplish the same thing.

   common truss:

   View Image

   raised or energy truss:

   View Image

1. 
   blue_eyed_devil | Sep 11, 2005 08:04pm | #3

   Stuart, in the olden days, all heels were desingned with that 4 1/4" in mind. When the energy shortage hit (79-80), many started focusing on the amount of space in the attic for insulation. The term "energy" heel was born.

   It's possible to have a scissor truss that has a 4" heel or a larger "energy" heel. All truss companies are capable of designing them.

   blue 

3. 
   BossHog | Sep 12, 2005 01:06am | #4

   The pics Stuart posted are pretty good.

   The so-called "energy heel" trusses are more expensive than those with a regular heel. So we don't so many of them around here. I suspect they're more popular the farther north ya go.

   Is that what ya wanted to know, or were you looking for more detail?

   Did you ever notice: When you put the 2 words "The" and "IRS" together it spells "Theirs."
1. 
   MikeSmith | Sep 12, 2005 01:25am | #5

   all of the trusses we use have energy heels... typically  a 12" heel

   and we use a lot of scissors trusses to give cathedral ceilings

   here's a scissors truss on top of a gambrel kneewall

   View Image

   4/12 top pitch... 1/12 bottom pitch..

   rule of thumb for scissors is minimum of 3/12 difference between the pitches

    

   Mike Smith Rhode Island : Design / Build / Repair / Restore

   Edited 9/11/2005 6:26 pm ET by MikeSmith

1. 
   basswood | Sep 12, 2005 02:34am | #6

   Mike, BossHog, and others,Thank you for the helpful info. I was unclear on how those energy heels would work as part of the truss structure. Looks like solid blocking in the truss design between bottom and top chords where they meet at the top plates. I get it now. Looks like the wall sheathing overlaps the energy heel above the top plate. Does this eliminate the need for hurricane clips? Also means you have to have your truss measurements just right to line up energy heals with top plate o/s edges...hmm.

1. 
   MikeSmith | Sep 12, 2005 03:16am | #7

   we tie the heel with the sheathing above the plate...

   that should take care of the clip requirement..

    but we also add some h2.5's on the inside at the plate..

   keeps the BI smilingMike Smith Rhode Island : Design / Build / Repair / Restore

2. 
   BossHog | Sep 12, 2005 04:04am | #9

   "Looks like solid blocking in the truss design between bottom and top chords where they meet at the top plates."

   Not always - Depends on the designer, and how the company likes to do it. Sometimes there's a short vertical web, anda diagonal web coming down to it.

   " Looks like the wall sheathing overlaps the energy heel above the top plate."

   I've only seen that done once or twice. It could be a regional thing, or just the preference of that particular builder/framer.

   " Does this eliminate the need for hurricane clips?"

   I doubt it. You couldn't get enough nails in the end of the truss to do any good.

   "Also means you have to have your truss measurements just right to line up energy heals with top plate o/s edges."

   That may or may not be a big deal. Truss assemblers aren't know for being brain surgeons. and they're only paid slightly more than the kids who flip burgers. So if you order a 30' 0" truss, they might be off a bit or vary from one truss to the next.

   Personally, I wouldn't recommend it. But that's only my opinion
   My Wife asked me how long I was going to be gone on this business trip. I said, "the whole time."

2. 
   BossHog | Sep 12, 2005 04:04am | #8

   "rule of thumb for scissors is minimum of 3/12 difference between the pitches"

   Not necessarilly - I've never heard that before. Must be a regional thing?

   Around here it's typically assumed that the interior pitch is half the outside pitch. But that doesn't always work - It's just a starting point. Depends on the span, loading, and location of the sloped ceiling within the truss.

   I often get people who assume a difference of 2/12 between the top and bottom chords will wotk. While it might at lower pitches, it doesn't at higher pitches.

   The relative angle between the chords gets lower as the pitches get higher. And you start getting into problems with horizontal deflection.
   One should never generalize.

1. 
   MikeSmith | Sep 12, 2005 06:22am | #12

   so, ron...

   let's see.. some of our scissors have been

   12/9..... 9/6....... 4/1..... 8/5

   almost never have we used  half the exterior pitch... 

     you mean like  12/6...or 8/4 , right ?...

   seems very restrictive...

   i ask my truss company for guidelines when i design my truss roofs.. that's where i got the 3/12 pitch difference .. but they've never told me i had to have double

    Mike Smith Rhode Island : Design / Build / Repair / Restore

1. 
   BossHog | Sep 12, 2005 02:04pm | #13

   I wasn't trying to say that you were wrong - Just that your rule of thumb isn't universal. I've honestly never heard of the rule of thumb you guys use around there. But it's a good illustration of how things can vary from one area to another.
   Give me ambiguity or give me whatever.......

2. 
   MikeSmith | Sep 12, 2005 03:58pm | #14

   ron... i didn't take it that you were saying i was wrong.. i understood the regional thing..

   energy heel scissors truss are used a lot around here..Mike Smith Rhode Island : Design / Build / Repair / Restore

3. 
   basswood | Sep 12, 2005 04:54am | #10

   In your photo, why is the last (or first) truss the same as all the other scissor trusses...wouldn't a gable end truss be easier at the ends of the roof?Also do you ever order extra trusses and make a truss and block sandwich for the gable ends? Does that make sense?

1. 
   MikeSmith | Sep 12, 2005 06:16am | #11

   in this truss... the distance between the top chord & the bottom chord is close enough so a sheet of ply covers both.. there was no need for a gable end truss

   View Image

   also .. notice the bottom sheathing  ends at least 16" below the 1st floor plate ?..

    so the next row of sheathing will span to tie the first floor to the 2d floor for wind uplift

   carrying the sheathing over the plates and tying the energy heel also forms an insulation dam for the 20" of cellulose we'll blow in the attic

   a "truss & block sandwich " ?  what does it do ? 

   does it have anything to do with the ceiling ?  we furr our ceilings.....

   we often use a dropped gable end truss if we have a large rake overhang

   if the overhang is less than 12"  we just use a rake ladderMike Smith Rhode Island : Design / Build / Repair / Restore