Controlling heel height


rlackore
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I've manually placed some roof and ceiling planes. Now I want to add trusses and be able to control the heel height precisely. I know about trusses and the auto-build roof procedure, but it is often easier to place roofs manually. Messing around with the rafter depth is hit or miss, since CA doesn't allow independent control of how the rafter seat is cut. If anyone has a suggestion for me, I would appreciate it.

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I placed the roof planes with a 12" rafter, just as a starting point. If I draw a truss, the profile is completely screwed up, because CA doesn't know what to do with what is essentially too small a heel height. So, yes, the heel height is controlled by the roof plane; the problem is that with a manually drawn roof plane, I can't go back and modify the heel height, say to 16", which is a realistic figure and will allow CA to draw a satisfactory truss profile. Modifying the rafter depth doesn't do anything - with a 8" pitch on my manual roof planes, CA always calculates a 10-3/4" heel, no matter what my rafter depth is (even if I enter 100', it still calculates a 10-3/4" heel). So, I was hoping somebody knows another method of controlling the heel for a manually drawn roof plane. Or, maybe someone can confirm that I'm screwed, instead.

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Why can't you cut a section,  measure how too low or too high the roof is and then raise the roof that distance.  But I do understand that you are trying to specify the the height of the roof baseline height.....  it seems like we should be able to do that....  I understand that we can't,  not that I know of,  but it would be a nice feature.

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The problem with modifying the roof baseline is that with auto-framing turned on CA will raise the effective plate height to the new baseline height. I can turn off auto-framing, and then the sections will behave, but then I have to give up auto-framing.

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Robert:

 

To expand on how to control the heel height, first you need to decide what size truss chords that you want displayed when you build a truss.  The Chief degaults are 2 x 4.  If you plug a number into the raise/lower setting Glenn mentioned, you need to understand that Chief will add that setting to the vertical rafter depth (truss top chord) to arrive at the total heel height of the truss.  The heel height is measured from the top of a wall's outside main layer to the top edge of the top chord vertically above it.

 

If I have a roof with a 5:12 pitch and I want a 12" heel height, the setting that I need to put in the raise/lower box in the roof dbx is the desired heel height minus the vertical rafter depth (VRD) of the top chord.  For a 2 x 4 top chord at a 5:12 pitch, the VRD is 3-13/16".  Therefore, the setting to put in the raise/lower box is 8-3/16".  If you don't do it this way, and just plug in 12" in the raise/lower box, you'll end up with a heel height of 15-13/16".  In this case, Chief's 12" measurement is from the top of the wall (outer main layer) to the bottom of the top chord directly above it.

 

I created myself a table of vertical rafter depths for various 2x sizes and for pitches from 1 to 12.  I often refer to this when setting up the spec's for roofs in my projects.

 

post-191-0-43481100-1397095379_thumb.jpg     post-191-0-09157600-1397097411_thumb.jpg     post-191-0-73657000-1397097435_thumb.jpg     post-191-0-28270300-1397097554_thumb.jpg

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Curtis nailed it. Yes you can use Glenn's suggestion, but that does not give the OP what he wants. He wants to define the roof base line off of top plate. With Glenn's method, some mathematical hoops still need to be jumped thru.

You might want to make this a suggestion.

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Even when using Roof Baseline Polylines (RBP), you still need to understand what Chief does under the hood when using them.  In my example of using a 5:12 pitch with trusses checked and the top chord being a 2 x 4, Chief will build the RBP at 112-15/16" if the entry in the Raise/Lower from Ceiling Height (RLCH) is left at the default '0' value.  I should have clarified that in my example I have the ceiling height (rough) set at 109-1/8".  Therefore, getting back to the vertical rafter depth (VRD) part of how to position a roof, for a 2 x 4 at 5:12, the VRD = 3-13/16" [i.e., Chief built the RBP to the top of the top chord above the outer main layer at the top of the wall .... 109-1/8" + 3-13/16" = 112-15/16"].  The graphic below is shown only to show the VRD of the top chord of the truss.  The extra 12" wouldn't be shown if I redid the graphic.

 

post-191-0-40009100-1397140121_thumb.jpg

 

Without knowing what goes on under Chief's 'hood', an inexperienced Chief user is going to being burning up some extra time to get their roofs positioned at the proper elevation.  The only other simple way (but this takes a little time to do) to get your roof planes at the desired elevation is doing what Scott suggested .... take a section through the wall/roof connection and use CAD and dimensioning as required to see how much you need to move the roof to get it at the desired heel height. 

 

Maybe it would be nice if Chief had a simple little graphic that would be accessible in the menu on the left side of the Build Roof dbx that would show users how Chief does this magic, similar to the graphic we get in the structure dbx when selecting and opening a room's specification.  Maybe we would need two graphics, one for trussed roofs and one for raftered roofs with birdsmouths.  Obviously, there could be a many  configurations that couldn't all be addressed with the graphics, but the idea would be just to show the user something simple to help them see what happens with the settings. 

 

post-191-0-78608600-1397139731_thumb.jpg

 

Maybe this should be addressed better in the manual (or Help) ... the information is there but you need to do some digging to put it all together.  Searching in Help for Roof Plane and/or Baseline will yield some good information.  I find that there should have been at least one more graphic shown (and the equation) for a trussed roof.  Actually, the rafter graphic shown might have looked better if the rafter was shown with the complete birdsmouth cut shown.  Maybe I am getting a little picky about this ... sooner or later, if users spend enough time working with this stuff they will learn what goes on when Chief auto builds roofs after all the settings have been plugged in.

 

post-191-0-62961700-1397141367_thumb.jpg

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The OP says, "I've manually placed some roof and ceiling planes."

 

It's the ceiling planes part that has me wondering.  We are giving him answers based on the ceilings being flat and at plate height.  Manual ceiling planes throw a new thing into play, like, if you have manually placed the roof and manually placed the ceiling plane under it, you have already set your heel, sort of.

 

You have done it for sure if you made sure your wall height and the springline for your manually-placed ceiling plane are at the same elevation.

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Thanks for the Tutorial Curt :) you must have heard me racking my brains and the help menus as I played around with this yest., so I have used your posts and images to make a small PDF Tutorial for when I really need it again :).

M.

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Glen and Curt,

 

I understand how to control things when auto-building roofs, but CA is poor in auto-building complex, multi-pitch, multi-height, multi-angle, multi-style roofs. In complex situations, it's much easier to draw the roof planes manually. Unlike auto-build, manual placement doesn't offer any control over the critical parameters prior to creating the roof plane; and after the manual roof is placed, the dbx is nearly useless in terms of setting up a consistent, accurate heel height. What I need is the ability to edit a roof plane and control the heel, seat cut, etc.

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Curt, thanks for posting the vertical rafter depth table, that is a huge time saver. The biggest beef I have with CA when it comes to designing roofs is that once you set a roof at a certain pitch, the baseline is placed in a position that if you change your roof to a different pitch, the roof is then in the wrong place. I end up deleting the old roof, changing the pitch, then re-drawing the roof rather than trying to figure out the new appropriate height based on the changed VRD value to keep the heel height consistent. Not sure if I'm explaining this well... In any case, if you draw a 12:12 roof with a 6" heel height at the correct location and then want to change it to a 6:12 pitch, the heel height will not be correct.

This seems like another case where the software is driving the construction, rather than the other way around. I think there should be a heel height entry option on a roof that would allow you to define the height of the heel from the top plate to the top of the top chord without having to determine the VRD independently.

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Sometimes the bottom line on getting your roof planes right, especially where different pitches are involved, is getting your fascias to display where you want them.  If different fascia heights are called for, then you may have to deal with your settings on a roof plane by roof plane basis depending on what your design calls for. 

 

My posts were mostly an effort to explain how Chief builds a roof and how the vertical rafter depths play a role in where the roof baseline ends up.  For those that already understand that, then you probably know as much or more on how to build roofs than I do.  For those that didn't understand these relationships, then hopefully I helped some users graduate to the next step in roof building, which I believe for most newer users, is knowing (and understanding) how to build roofs manually. 

 

When I first started using Chief back in 2001 with v7, I wanted all my roofs to build automatically.  I had virtually no experience with CAD programs at the time so admittedly, I wanted Chief to magically do almost everything automatic.  I had a fear factor about learning how to do roofs manually.  A trip to Coeur d'Alene and an hour with Mont Stephenson was what broke the ice for me.  It is actually a very easy process if one can just learn some of the basics of how Chief functions depending on the settings being used.  One thing that I still do on a regular basis is create simple test plans, input the settings I believe are correct and then view the results with a cross section of the roof/wall connection.  This takes very little time ... you aren't messing with your project's plan ... if the results are satisfactory, then I know what settings to use in my project plan. 

 

I think for the most part Chief's roof tools work very well and I have been able to deal with all the roofs I have had to build without problems.  I may be testing that statement a bit with a project I am just starting that has several circular turrets and steep roof s on them as compared to the rest of the plan.  Lots of exterior detailing etc. ... something I have not had to tackle in the past.  I suspect I will be doing quite a bit of sectioning of roof connections to make sure things are building the way I want them.  Looking forward to the challenges this plan has for me.

 

By the way, I understand that Mont is now retired.  I wish him well ... he was a builder for lots of years and it took a toll on him.  I appreciate your getting me over the "roof hump" way back when ... good luck and best of health to you.

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Curt

I also start all my plans with a test , I will draw a standard box, then setup whatever roof in going to use and set all the roof defaults, Then set all the other defaults, delete it, and start laying out my floor.

I like working the roof out first.

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  • 1 year later...

this topic baffles me too. 

 

til now i just find Curt Johnson's method works best for me. and that is raising it 12".

 

here another issue i have with this topic....

 

i alway need 2 difference heel height on my plan.

 

1  @ 12" for the main roof of the house.

and the other heel height @ 0" for the attached garage.

 

i always just Auto build @ 12", then manually lower the the garage roof to what i need.

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Ohhhh great :)   thx Allan.

 

Pitch is in Degrees  

 

I usually use this Site for conversions and Round off to nearest full Degree     eg 10/12 is 39.81  so  40°deg.

 

http://www.blocklayer.com/PitchAngle.aspx

 

***edit  found my other Cheat Sheet to convert Roof Pitches  , see post below.

 

 

Hopefully the Oz and Kiwi Architects will agree once they are online :)

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Robert:

 

To expand on how to control the heel height, first you need to decide what size truss chords that you want displayed when you build a truss.  The Chief degaults are 2 x 4.  If you plug a number into the raise/lower setting Glenn mentioned, you need to understand that Chief will add that setting to the vertical rafter depth (truss top chord) to arrive at the total heel height of the truss.  The heel height is measured from the top of a wall's outside main layer to the top edge of the top chord vertically above it.

 

If I have a roof with a 5:12 pitch and I want a 12" heel height, the setting that I need to put in the raise/lower box in the roof dbx is the desired heel height minus the vertical rafter depth (VRD) of the top chord.  For a 2 x 4 top chord at a 5:12 pitch, the VRD is 3-13/16".  Therefore, the setting to put in the raise/lower box is 8-3/16".  If you don't do it this way, and just plug in 12" in the raise/lower box, you'll end up with a heel height of 15-13/16".  In this case, Chief's 12" measurement is from the top of the wall (outer main layer) to the bottom of the top chord directly above it.

 

I created myself a table of vertical rafter depths for various 2x sizes and for pitches from 1 to 12.  I often refer to this when setting up the spec's for roofs in my projects.

 

attachicon.gifEnergyHeelSection.JPG     attachicon.gifEnergyHeelBuildRoofDbx.JPG     attachicon.gifEnergyHeelTrussSettings.JPG     attachicon.gifVertRafterDepths.jpg

Awesome cheat sheet Curt. Thank you for sharing it.

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