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# How to control two roof faces intersection ?

## Question

Hello,

I have two roof faces - highlighted in orange. I want them to intersect on my red intersection line as shown below. In other words, I want my edges A and B to be tilted - not vertical. Is there a way to do this ? The goal is to have nice continuous components in Section VP.

I would appreciate your advices.

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14 hours ago, Kevin K said:

One other thought....from my experience as being a designer / builder in a galaxy far far away at one point in time....Flat roofs have to drain....which means the roof can't be dead flat, unless you slope it in various directions towards drains within the flat roof mass...which has its own set of problems to let the water exit.

I am sure Stephane will be yelling at me for bringing this up. 🙂

I would never yell at someone that is kind enough to share his experience.

In order to answer to this, I think the question here is not that much how to build roofs, but how to draw roofs.

The original topic : "How to join two roof faces ?". We found out that it was possible to do it for simple structures but not for complex ones (where "complex" stand for 1) roof with a hole; 2) intersection not perpendicular to the edge; 3) 0.000000° flat roof). This means that most of the times the tools to join roof faces are not usable

We all agree that flat roofs are never completely flat, because water need to drain and requires a minimum slope of 1.5%. When we say flat roof we actually say 1.5% tilted roof (Note that this 1.5% slope is not necessarily the last layer). For drainage it is not negligible; but for the drawings up to 1'':10'00'' (+/- 1:100) it is completely negligible. On bigger scale, we draw 2D details anyways.

There are many reasons why we want to draw dead flat roofs :

- As said, when we draw on small scales, at early stage of the project, where you still don't want to think about these details.

- Then maybe, the first component and the last component are dead flat. The slope is given by a component in between.

- Imagine you are crazy enough to draw your slope with the Drainage Tool on Slab, then you draw your slabs (which would be your roofs) completely flat and you give then the drainage slop with the Drainage Tool. Also, keep in mind that we actually draw tilted slabs with roofs because the Drainage Tool is a nightmare to use (I would say the issues are a bit similar to our "how to join two roof faces": it doesn't work when things are getting complex), but this is another topic.

- The main reason is this one : tools are not usable to control slopes accurately ! And this is again why you don't draw your flat roof with a drained slab.

16 hours ago, Tom W. said:

It's a shame because you can manipulate/control Slabs in all sorts of satisfactory ways: using wall hole components, clipping components,  adding/subtracting 3D objects, sloping the surface, tapering components, create solid section from grade object, lots of control over individual edge conditions, etc. Be great to have the same flexibility with roofs. 'Roof/Slab Modernization' was in the road map but in the 'Active Research' section...

I cannot agree more, with a reservation regarding the Drainage Tool ("sloping the surface") which is, in my opinion, unusable.

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6 minutes ago, Stéphane said:

I cannot agree more, with a reservation regarding the Drainage Tool ("sloping the surface") which is, in my opinion, unusable.

That's interesting I thought Slab Drainage tool worked quite well when it came to putting the falls on a flat roof or a concrete yard or whatever...? What I thought didn't work so well was when you wanted to include drain symbols:

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I've never really tried the slab drainage tool - what advantage does it offer over the roof face tool?

The things I find useful about the roof face tool:

- it can give me a multi-layer buildup

- its outline shape can be quite easily edited in top-plan view

- it can give you an extrude-type object with vertical edges

- it's quick and easy to adjust and keep track of the pitch, and Z reference

These things are all advantages over using solid-modelled objects. So, even though the ability to tune the edge offsets is a big limitation (as are the problems with joining faces) it is sometimes quite useful... particularly in the early stage of projects (means that I can quickly work out the implications of different roof pitches etc) and I do sometimes use it to a limited extent in construction level-drawings, sometimes overcoming the edge problem by having a roof buildup up actually made up of a group two roof face objects, one dealing with the outer parts and one dealing with the inner parts.

But can the slab drainage tool offer the things I list above, plus something extra?

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7 minutes ago, Tom W. said:

That's interesting I thought Slab Drainage tool worked quite well when it came to putting the falls on a flat roof or a concrete yard or whatever...? What I thought didn't work so well was when you wanted to include drain symbols:

It's a bit the same issue we have for connecting roof faces properly : It works only for simple structures. When you get a more complex one, best case : you spend a whole day making it work exactly as you want to; next day your engineer send you an e-mail saying that you cannot and need to spend another day to correct it. Worse case : it doesn't work.

This exemple sounds a bit stupid but that's actually the very reason why you don't solve these issues at the beginning of the project. And that's why we need to be able to draw drained slabs or roof completely flat, first. When the project is getting stable enough, you start going into the details.

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19 minutes ago, line-weight said:

But can the slab drainage tool offer the things I list above, plus something extra?

I think @Tom W. summarize pretty well the extras here :

17 hours ago, Tom W. said:

It's a shame because you can manipulate/control Slabs in all sorts of satisfactory ways: using wall hole components, clipping components,  adding/subtracting 3D objects, sloping the surface, tapering components, create solid section from grade object, lots of control over individual edge conditions, etc. Be great to have the same flexibility with roofs. 'Roof/Slab Modernization' was in the road map but in the 'Active Research' section...

19 minutes ago, line-weight said:

The things I find useful about the roof face tool:

- it can give me a multi-layer buildup

- its outline shape can be quite easily edited in top-plan view

- it can give you an extrude-type object with vertical edges

- it's quick and easy to adjust and keep track of the pitch, and Z reference

And this is exactly why I prefer the Roof Tool over the Slab Tool to make my underground parking slabs, where drainage slope are not negligible anymore, and easier to do.

Edited by Stéphane
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12 minutes ago, line-weight said:

But can the slab drainage tool offer the things I list above, plus something extra?

Do you mean for a flat roof? If so yes that's what it's designed for: to put in the various falls + drainage points.

Or for yard areas where you have a similar arrangement of falls/drains.

Or factory floors with floor drains.

This kind of thing:

But as I said in the thread I linked the drainage symbol component doesn't really work

However I should say this is just from messing around with these tools, I haven't used them in proper projects.

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2 minutes ago, Stéphane said:

And this is exactly why I prefer the Roof Tool over the Slab Tool to make my underground parking slabs, where drainage slope are not negligible anymore, and easier to do.

That's really interesting. Like I say my experience is pretty limited but really useful to learn all this

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17 minutes ago, Tom W. said:

Do you mean for a flat roof? If so yes that's what it's designed for: to put in the various falls + drainage points.

Or for yard areas where you have a similar arrangement of falls/drains.

Or factory floors with floor drains.

This kind of thing:

But as I said in the thread I linked the drainage symbol component doesn't really work

However I should say this is just from messing around with these tools, I haven't used them in proper projects.

Does it limit you to a flat underside? So it suits flat roofs built up on truly flat structure, where you introduce the fall through tapered insulation or similar - but not where the structure itself is pitched?

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Yes that's absolutely right. You choose which components you want to taper but you can't taper the underside of the bottom component - but like you say, you wouldn't really want this anyway. Then it becomes a pitched roof rather than a flat roof.

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• Vectorworks, Inc Employee
On 12/11/2020 at 10:09 AM, Stéphane said:

After having done several tests, I would share your conclusion. It is dysfunctional.

- doesn't work if your roof has a hole in it

- doesn't work if one roof face is flat

- doesn't work if the intersection is not perpendicular to the roof edge

On 12/11/2020 at 10:15 AM, Stéphane said:

Last thing we could do is ask @Matt Panzer for some inputs maybe...

These do all sound like bugs, but we'd need to see example files to be sure there are no technical limitations involved.

Could someone please send a simple file that shows these issues via BUG SUBMIT ?

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I posted a file on the thread that I started 6 months ago. It is still there and available for anyone at VW to enter into the bug submit process, if they find they can replicate the problem, as it has been for half a year:

Edited by line-weight
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Wait.....did Matt Panzer just call me dysfunctional??    🙂

One issue regarding a basically flat roof....it does need to drain.  Code-wise, in most States in the USA the building departments mandate that there should be a minimum slope of 1/4 “ per foot, to make sure the water drains from the roof surface. So, you could just drain the flat roof all in one direction, but then the fascia on a basically flat roof would have a very slight slope to it, which doesn’t look that nice. In my building experience, in my Contractor days, to resolve this, I would basically create a VERY low sloped hip roof on top of the flat roof, which allows all the water to drain off in all directions towards the edges of all the roofs, so all the roof fascia boards are totally horizontal. From the street, for example, looking up to the roof, it appears dead flat.

This technique also means you do not have to use any slab tool drainage system. Obviously if you have a parapet style roof things are a bit different, but for most instances involving theoretical flat roof, I found my solution works quite well.

You can draw this the same way in VW. I am reading on myniPad at the moment so I can’t do a screenshot, but I will a bit later.  I think you guys probably understand what I am describing?  All this said, this has nothing to do with the roof joining issues in VW, but more to do with the reality of draining a flat-ish roof surface.

Thoughts?

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2 hours ago, Kevin K said:

Thoughts?

Hi @Kevin K I've done 'flat' roofs in the past (real ones I mean, not VW ones!) with shallow falls + valleys + internal drain points, the falls created by the insulation like @line-weight says. And I'd say the slab drainage tool is tailor-made for drawing these types of roofs - very quick + easy. This is a roof with parapet walls + inward sloping falls

The only issue I have with the slab drainage tool is the drain symbols which don't insert at the correct elevation + are a pig to get in the right place.

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Tom......did we forget the attachment?  :-)

"This is a roof with parapet walls + inward sloping falls"

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Ha ha no I just meant the roof I was describing was like this! You'll have to use your imagination I'm afraid! 😁

Although I will see if I can find a photo of it seeing as this thread is rapidly becoming an homage to flat roofs...

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@Kevin K I think it comes down to whether you want a tapering layer in the buildup. If the roof you describe was built up in such a way that the fall was generated by, say, tapering insulation, then it sounds like the slab drainage method would be best. If it were built up with some kind of rafters at a slight pitch and then a false ceiling, perhaps the roof face method (plus something else for the ceiling) would be better.

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Oh, don't bother.....I just thought you boinked out and forgot the attachment   :-)

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• Vectorworks, Inc Employee
2 hours ago, Kevin K said:

Wait.....did Matt Panzer just call me dysfunctional??    🙂

🤣

I think you might be reading between the lines that are already between the lines.

I assure you, I didn't put those lines there.  😉

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hahahaha.....I knew that.   Just messing with ya. :-)

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line-weight

Totally true on both your points..

Flat roofs require some consideration in the real world of actually building them.

They are always a bit tricky.

I believe I had mentioned in an earlier post, regarding the roof tool, I almost never just use an overall thickness for the roof, but rather just the roof sheathing thickness, then the actual 3d roof rafters.  I know some would consider this extra work, but honestly it does not take that much more time, PLUS, by creating the actual roof rafters, they all show up correctly in sections....you don't need to annotate the living hell out of the sections to show the actual rafters. That said, this is just my preferred methodology. I even include the framing in my working drawings.  The contractors and builders really appreciate that, so at a glance, they can get a good idea how to frame the roof, etc.

I am not suggesting that everyone should adopt it.  :-)

Case in point.....

.

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Matt

We have all come a long way.

I remember the old days when I would have to call you on the phone and have you explain to me how to use 'Doodle". !!   :-)

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While we are on the subject of roof faces:

Is there an inconsistency in the way class visibility works, compared with floor slabs and walls, or am I doing something stupid?

For example: if I have classes:

object_wall

object_roof

object_floor

material_A

material_B

- Then I have a wall, with 2 components, one is assigned to material_A and the other to material_B

- I put the wall object in class object_wall

- Then I set class material_A = visible, class material_B = invisible, class object_wall = visible

- I set the wall object to render by component

- Then what appears is the wall, but only with the component set to material_A actually visible.

- Of course, if I set the class object_wall to invisible, nothing appears at all.

But if I follow the same procedure with a roof face object, something different happens.... the component that is supposed to be invisible is visible.

Is that something that someone else can replicate?

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25 minutes ago, Kevin K said:

the actual 3d roof rafters.  I know some would consider this extra work, but honestly it does not take that much more time, PLUS, by creating the actual roof rafters, they all show up correctly in sections....you don't need to annotate the living hell out of the sections to show the actual rafters. That said, this is just my preferred methodology. I even include the framing in my working drawings.  The contractors and builders really appreciate that, so at a glance, they can get a good idea how to frame the roof, etc.

I am not suggesting that everyone should adopt it.  🙂

That's exactly what I do: it also helps me get my head around what's going on structurally.

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@line-weight I gotta read all that again pertaining to your quandaries regarding components, etc.  I got dizzy reading it. ;-)

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I will say I am not a fan of components.....I am more of a 'by object' guy.

My whole system for layers and classes would probably blow all your minds....it is so elegantly simple.

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