michaelgia

Trick is having them at a proper distance to each other before blocking.

Those formulas don't work.

As an example:

When you increase your overhang the the truss's top chord stays put but extends and therefore drops your soffit level.

At this point you have to increase the raise off plate value by measuring or calculating the vertical rise in the isosceles triangle determined by the soffit and roof pitch with the new extended length of the hypotenuse.

I'm still stubbornly working on it.

Oh. Ok. I get it. That's why initially the value would make sense until I checked trusses no Birdsmouth.

Sorry about that.

Still wish I new where to locate the soffit level with respect to the Vertical Structure Depth.

...that's what I thought initially.

Trust me when I tell you - experiment a bit and you'll be astonished as to how it's not what you say it is.

It's insane.

But, I will take your advice and stop chasing this one.

I'll simply draw a roof, measure the height I need to raise in cross section and then input that value.

It still bugs me though.

Regarding the vertical structure depth, that's simply the vertical measurement (measured along the z-axis) of whatever you have in your Roof Structure Definition dbx.

First, thanks for your patience. I will stop my pursuit of a simple answer.

Regarding Vertical Structure Depth, I'm afraid your definition does not really define anything. Or I'm not understanding.

Also the reference manual does not seem to have a definition for it either.

It's value automatically changes with each new roof pitch entered though.

Try to locate it in across section. It's ephemeral.

Can you explain or define the "Vertical Structure Depth", in the Build Roof dialogue box?

I thought I knew, but it's really a bizarre value seemingly unrelated to anything in a cross section. At least not consistently.

Sometimes it's the distance from the top plate on the inside of the exterior wall up to the top chord, and sometimes it's not?!?

I'm hoping this value could shed some light on what's going on.

Still the biggest riddle is controlling the height of the soffit level.

I wish there was a "distance to top plate" for every item of a roof. That would simplify everything.

Or use an absolute elevation as a reference to figure everything else out.

Has Chief never heard of a simple A-frame truss that sits atop of a wall? Am I taking crazy pills here?

Oops, I meant pitch in degrees divided by 2.

As I said before, quite surprisingly, a close approximation is pitch in degrees x 2.

and that's why I'm convinced the angle of the roof together with Chief's secret Birdsmouth bloody value is the way to go.

Thanks Michael, I guess that's probably the state of affairs and I need to stop chasing that one.

I'm just not convinced there isn't some way.

If you open up the Build roof dialogue box you'll see that depending on the pitch you enter, you'll see Chief automatically update a corresponding greyed out value for Raise off Plate. Then when you put a check on "Trusses (no Birdsmouth) the value of the Raise off Plate goes to zero.

So, I was hoping that before it goes to zero I could use that value in a formual to get my Trusses (no Birdsmouth) to raise by the proper value to get the condition I was looking for.

I'm not sure I'm following why this has to be so complicated. Have you tried simply taking a cross section view and just measuring the distance between the top of your plate and the bottom of your sub fascia? That should

Be the number you need right?

-Yes that is correct.

That is what I normally do.

And I'm sorry I'm leading everyone down this rabbit hole, but I was hoping I could find a quick and easy formula based on values that I already see staring at me when I open up my roof dialogue box.

Example "vertical structure" x "magic ratio" = raise off plate height.

this way I don't have to constantly go back and forth between dialogue boxes and cross sections to measure and calculate.

Sounds crazy, I know

isn't the soffit height defined by the sub fascia?

Ok so, you take your fascia top height as Glen said then you say subtract sub fascia height and then we should have soffit height. Great.

But, translate that value and give me the corresponding raise off plate value so I get the condition I'm looking for.

Not so easy. At least I can't figure it out.

A lower soffit would actually increase the ratio of window/door opening and be worse for the ratio, so you are right, but all they see is that your plans are not accurately representing the finished home and they interpret this only as deception.

That's how things roll around here.

...anyone figure out a formula yet?

Or have an explanation as to why Chief would not at least reveal how they determine where they drop their soffit level with respect to the pitch?

I'm sure I'm missing something but I can't for the life of me figure out where this is buried or if it's staring right at me?

One of the main reasons for all this headache is that the city needs a measurement from ground level to just under soffit to be able to calculate exterior wall surface as a ratio to window and door opening surface. We need for that ratio to be under 30%.

They're very strict, and seeing that clients want bigger and bigge windows I'm sometimes very close to that limit.

When my soffits are off and they notice, then they think I'm cheating by dropping the soffit levels.

...yes, I've been up all night racking my brain over this.

Am I missing something here.

Why can't you just build a normal roof with a boxed eave.

Measure the distance between the eave soffit and the ceiling.

Enter that distance in Raise/Lower from Ceiling Height.

Too funny. You are absolutely right and that is how I do it presently. I was just hoping that I cloud find a formula as a relationship to some Chief value in the roof dialogue box that would give me that "raise" height so I don't have to go through the steps of

1) draw roof

2) take cross section.

3) measure

There must be a trigonometric relationship between the mysterious "vertical Structure Depth" value and the value I'm looking for to raise off plate.

By the way I've found that the vertical structure depth is actually the distance between the inside of the wall framing and the top of the roof truss measured vertically. Kind of the sister of the baseline height. But measured from the inside of the wall as opposed to the outside of the exterior wall.

@michaelgia

What overhang are you using?

I'm using 24" overhang but as Bill mentioned it doesn't matter. Which is true.

However, the baseline height can not be used in any formula. I plotted the values in a graph. They produce a steep positive curve, so the relationship is not linear.

It absolutely is related to the angle of the roof pitch which causes the baseline height to increase in value every time you change youre pitch. However this raise is offset by the magical fairytale value that Chief has built in to its calculation for its default Birdsmouth trusses that it calculates. That is the distance below the top plate that it's soffits are drawn at, which also changes with the pitch of the roof.

If you use Bill's formula you'll see that it produces random distances between the soffit level and the top plate. He is right that it will produce a cantilever truss when you draw it but the soffit height is all over the place.

I'm just trying to reproduce how we build in the north east.

And that is, 9 out 10 times your truss's bottom chord sits on top of your exterior wall and overhangs out to create the soffit surface that your Aluminium guy will nail his vented soffit material. Sometimes we'll add a 2x4 under that surface and set it back 1.5" to give what we call a double soffit etc..., but that's just for esthetics.

It's crazy that there isn't simply a radio button to produce this extremely common way to build. I'm pretty sure that even in California these days they understand that you need some space for ventilation between your top plate and your roof surface. Don't they?

A good approximation surprisingly is:

(Pitch in degrees)/2

Example 5:12 = 22.5°

22.5/2 = 11.25" for raise off plate value.

Exact value is 11-3/8"

Example 9:12 = 37°

37/2 = 18.5" for raise off plate value.

Exact value is 18.5"

Example 10:12 = 40°

20"

Exact value is 20-5/16"

It works for me with any pitch, and any overhang.

No it doesn't...

Select boxed eave and you'll see that your soffit is a couple of inches below the top plate.

I was hoping it was as simple as that but it's not.

I put together a table and I'm trying to figure out the correlation but I would need to dig up the bones of Bernouli to figure this out.

I think if there is a formula you would have to involve the automatic birds mouth "raise off plate" value and then figure out how that affects the distance you need when you check "Trusses (no Birdsmouth)".

In other words, what is the Chief secret formula for distance above plate when they generate their default Birdsmouth trusses. This value should provide an easy formula for the raise off plate value when you want a cantilever with soffits same height as top plate.

Here is my table: (for a few of them)

Pitch 3:12 --> Raise of Plate = 7-11/16"

Pitch 5:12 --> Raise of Plate = 11-3/8"

Pitch 7:12 --> Raise of Plate = 15"

Pitch 10:12 --> Raise of Plate = 20-5/16"

Pitch 12:12 --> Raise of Plate = 23-11/16"

Pitch 16:12 --> Raise of Plate = 30-5/8"

....anyone have Stephen Hawking's number?

Close but no cigar. Or maybe I'm not explaining myself.

To get the condition I'm after on a 3:12 pitch I need to raise off plate by 7-11/16" so that my soffits are same height as my top plate.

A true A-frame cantilever. That is, my bottom chord cantilevers and extends past my exterior wall framing and forms the soffit.

Just realized it also depends on overhang as well.

My head is spinning.

3 variables:

X) pitch

Y) overhang

Z) raise off plate value

Unless it's that vertical structure depth value...

Do I just use that value to raise off plate?

(In build roof dialogue)

Has anyone ever made a table for values to raise above top plate per pitch?

That is, example, for pitch 6:12 raise 11" etc...

So we have a nice and neat table with two columns.

pitch X:Y = +Z"

So that the bottom chord sits neatly atop the top-plate.

I guess pitches 3 through 12 would be sufficient.

And it's not as easy as it sounds.

You have to mess around with drawing a truss and looking at it in a cross section view until the truss sits exactly on top of the top plate.

I wish Chief could provide at least a formula for this.

It's trial and error and I never really know if I have the exact value or I'm just in the ballpark.

Sorry, I can't help you but you absolutely have the greatest toolbar setup I've ever seen!

Can you share please?...

It's so logically laid out. You're definitely an autocad user.

Good job!

...as a contractor I have just as many customer stories.

Over the past few years customers are getting quite comfortable and savvy at shaking down their contractor.

regular wise guys

I think, however it's more common in larger metropolitan areas. The public is way two sly.

But, of course since television is geared towards the viewing public it's always that incompetent crooked contractor story we hear, never the customer who is weasling their way out of paying full price.

Oops forgot to post response.

To get winders without the fillet you have to draw three separate landings.

Actually I draw one square landing between two sets of stairs that are at 90 degrees to each other so I get the automatic height on the first landing correct.

Then I copy the landing two other times adjusting the height an extra riser height each time.

Then I re-shape each landing to the pie shape required to get those perfect 90 degree pies all meeting at precisely one point as in your photo.

Then I block the mother and stick it in my user library.

Always easy to add or remove steps on the straight stair parts.

I can even rotate to get "U" shape staircase with one square landing and a set of three winders.

(That's for when you really messed up on your head clearance. lol )