topic Re: In AC17, can walls clean up to roofs as well as to slabs in Modeling

In AC17, can walls clean up to roofs as well as to slabs?

Eric Bobrow — Tue, 23 May 2023 12:36:00 GMT

I was asked by a client to troubleshoot a section in AC17, since the walls did not clean up in section to the deck.

After some testing, I found that the new Building Material-based intersection management seems to only work for walls meeting slabs. In this case, the deck is sloped so it is done with a composite roof, which meets a lower wall and a parapet wall.

Here is an image of the original model intersection along with a copy of the same walls meeting the same composite when placed as a slab instead of a roof. In the case of the slab, the intersection cleans up pretty well in section.

When the roof meets the walls, it doesn't clean up at all with the new building materials. The best I could do is to use Solid Element Operations (as seen in the image), and even then, the roof sheathing sticks into the wall rather than stopping at the core framing of the wall.

When I tried using the Connect command, the walls got trimmed back to the edge of the roof, which only extended to the outside of the core; thus the walls then lost their sheathing, which looked totally wrong. I tried moving the roof pivot line to the outside of the wall face, and changing the Trim to Roof option in the Roof Settings to Pivot Lines Down, but that didn't help restore the wall sheathing - it still was removed by the Connect command.

Does anyone have any better suggestions for getting a good cleanup with parapet walls meeting roofs in AC17? At this point, it looks like one will need to use SEO and then a patch to clean up the intersection.

Eric

Re: In AC17, can walls clean up to roofs as well as to slabs

Anonymous — Mon, 01 Jul 2013 04:47:24 GMT

Eric,

I cannot comment on AC17 as it has not yet been released in Aus yet, but generally I would model it as you would build it.

If concrete deck with screed+membrane+ballast/finish I would build a wall to the underside of the slab then another wall for the parapet wall (as is unlikely that the parapet wall will have the same construction as the wall below - no insulation / different linings) and use a mesh over the top for the topping screed and a composite roof for the membrane+ballast/finish

If metal deck roof I would again build the wall in two parts as per above but would also draw a third wall for the parapet linings as these would not continue below the roof decking.

Probably a bit more work but gets the required results and you have an accurate model.

Regards,
Scott

Re: In AC17, can walls clean up to roofs as well as to slabs

Laszlo Nagy — Mon, 01 Jul 2013 10:41:04 GMT

For Priority Based Intersections involving any Roof, Shell or Morph element, the intersection is not created automatically just because the elements intersect in 3D.
The Connect\Merge Elements command (from the context menu) needs to be used to explicitly establish the connection:

https://www.youtube.com/watch?v=V_8CJT8TWik&list=PLnXY6vLUwlWWa_BD5mX2l2YujV_CMtXFO&index=7

However, this may only be part of the resolution of this particular case. Examining this situation brought to my attention an aspect of how Priority Based Conections work which I am not sure is mentioned anywhere in the New Features Clips or in Help. So I share it with you here.
It concerns how ArchiCAD calculates which skin is stronger.

The reason the Wall structure does not cut skins of the Roof is because the Roof's skins are stronger, they have a higher intersection priority number.
But the trick is here: let us say you have a Wall skin with an Intersection Priority Number of 600. Let us say it intersects with a Roof that has 3 skins with Intersection Priority Numbers 700, 500 and 800. One would expect that the 700 and 800 skins of the Roof to cut the 600 skin of the Wall, while the 600 skin of the Wall to cut the 500 skin of the Roof.

What I found is that this is not the case: since the 500 skin of the Roof is situated between two skins that are stronger than the 600 Wall skin, therefore this weaker skin between those stronger skins will also cut the 600 Wall skin, despite that it is a stronger skin.

This gives a rule for us: To avoid such situations, as we progress from the core of a structure (or from the skin of the structure with the highest Intersection Priority Number) outward the Intersection Priority Numbers of skins should be progressively less and less.

So this would be good:
300
400
500
800 (Core)
500
400

But this could cause unexpected results beause of the above stated reason:
600
400
500
800 (Core)
500
400

Please let me know if this resolves this issue.

Re: In AC17, can walls clean up to roofs as well as to slabs

Eric Bobrow — Mon, 01 Jul 2013 20:40:31 GMT

Laszlo -

Thank you so much for posting that information! I was unaware of the Connect > Merge Elements command.

I was able to select the two stacked walls and the roof in section, and use this command, and they cleaned up exactly as the slab example did! Hooray!

In this case, there were no issues with Intersection Priority Numbers of the skins having values that did not progress properly from weaker to stronger. However, your explanation of this potential issue is important for troubleshooting composites that are created by users or migrated from previous versions of ArchiCAD.

Eric

Re: In AC17, can walls clean up to roofs as well as to slabs

Laszlo Nagy — Tue, 02 Jul 2013 07:14:42 GMT

Welcome, glad it worked out for you.

Re: In AC17, can walls clean up to roofs as well as to slabs

Anonymous — Wed, 18 Jun 2014 14:19:37 GMT

Hello,

I can't seem to get these roof/wall connections right. Using the new merge tool, here's what I can do. I added the priorities on the picture.

What I would like AC to do is connect the concrete together and get the insulation all around the exterior of the concrete.

What am I doing wrong?

Re: In AC17, can walls clean up to roofs as well as to slabs

Laszlo Nagy — Wed, 18 Jun 2014 15:49:28 GMT

Make the Intersection Priority Number of the insulation's Building Material stronger that that of the Concrete.

Re: In AC17, can walls clean up to roofs as well as to slabs

Anonymous — Thu, 19 Jun 2014 07:36:18 GMT

Hi,

I tried it, as you can see. I'm almost there, but not quite. What's the next step?

Also, it seems weird for the rest of the project to have this priority logic: insulation higher than concrete. Would it be common practice to use two different insulation materials with only priority varying?

Re: In AC17, can walls clean up to roofs as well as to slabs

Anonymous — Thu, 19 Jun 2014 14:30:48 GMT

you need to make the the external render a higher number than the concrete too, so that it cuts it correctly.

It takes some getting used to for the PBC logic but yes, you will need different insulation (and other) materials for different situations. they can have the same properties but with different PBC numbers.

It seems complicated but once you have your materials list set up it should all come together and will be powerful in creating correct junctions.

I would love to see people sharing materials lists.

For your project I would create a roof insulation material and a wall insulation and external render materials. The wall insulation and render materials would have a higher PBC number than the concrete the roof insulation material. I would then bring the height of the wall up so that it is set to the top height of the roof. This way the insulation and external render will continue up to the top. Your roof finish layer can be higher than everything else.

Re: In AC17, can walls clean up to roofs as well as to slabs

Anonymous — Fri, 20 Jun 2014 08:06:02 GMT

Hi,

Attached is my new material PBC strategy. It works but requires a further SEO. I imagine that last step (which nonetheless makes the connection perfect) makes calculation slightly longer. Is there a way to avoid the SEO?

On another hand, now that I have different concrete materials for different priorities, all using the same solid red hatch, a line appears at the intersection between them.

Re: In AC17, can walls clean up to roofs as well as to slabs

Anonymous — Fri, 20 Jun 2014 08:15:59 GMT

Here's the junction working

Thank you very much for your help!

Re: In AC17, can walls clean up to roofs as well as to slabs

Barry Kelly — Fri, 20 Jun 2014 08:43:57 GMT

Instead of using 'Connect > Merge' and then doing an SEO try using 'Connect > Trim Element to Roof/Shell'.
This will do the SEO staight away.

Barry.

Re: In AC17, can walls clean up to roofs as well as to slabs

Anonymous — Fri, 20 Jun 2014 16:56:56 GMT

I understand this priority logic: exterior finishes > insulation > concrete. But then, that same wall in plan view, in the case of an inward angle, PBC goes wrong: exterior finish and insulation goes threw the concrete. I tried tweaking the priorities but can't find the right compromise for appropriate intersections in section AND plan. Seriously, what am I doing wrong?!

Re: In AC17, can walls clean up to roofs as well as to slabs

Anonymous — Fri, 20 Jun 2014 18:14:34 GMT

Can you post an image of the angle in plan view that isn't joining correctly?

Re: In AC17, can walls clean up to roofs as well as to slabs

Laszlo Nagy — Sun, 22 Jun 2014 18:59:11 GMT

This is problematic in my opinion because as you said, if it is good for a Section, it may not be good for Floor Plans and vice versa.
I tend to consider Floor Plans to be more important so I would set priorities which will give proper intersections on Floor Plans.
So for sections we need to find another solution.
What I am thinking is that you could create a Complex Profile for that Wall-Roof connection, then use it as a Complex Profile Beam. You could simply copy-paste the section fills you showed in your screenshot and create the Profile from that. You would place the Beam and the Beam would be the Wall-Roof intersection portion. The Wall would stop at the bottom of the Beam, the Roof would stop at the side of the Beam. I hope it makes sense.

Re: In AC17, can walls clean up to roofs as well as to slabs

Anonymous — Mon, 23 Jun 2014 08:01:14 GMT

Here's a view of what happens in plan if insulation priority is higher than concrete. The result was predictable..

Lazlo, I will try this profile method ASAP and will keep you posted. Anyway, thanks for the help. Do you know wether AC18 will have some kind of built-in solution for this kind of problem?

Re: In AC17, can walls clean up to roofs as well as to slabs

Anonymous — Mon, 23 Jun 2014 09:54:03 GMT

Hi,

The complex profile method seems to work pretty well. The only thing is I would love those additional lines to disappear. Any thoughts on that one?

It seems too bad to have to come back to a pre-AC17 method to accomplish something AC17 was supposed to solve. Let's hope AC18 can go further.

Re: In AC17, can walls clean up to roofs as well as to slabs

Laszlo Nagy — Mon, 23 Jun 2014 11:55:15 GMT

I would make the bottom of the Profile start at the bottom of where the two red skins join.
Did you decrease the height of the Wall so that the top of the Wall is at the bottom of the Beam Profile? Then the skin fills should merge with no lines.
Same goes for the Roof: the vertical left edge of the Roof should coincide with the right vertical edge of the Beam Profile. Everything left of the Roof and above the Wall should be profiled, including that little overhanging part of the Roof.

As far as I know, there is no such developments in priority based connections in AC18.
One thing to enhance L-joints is a new checkbox in the Wall Settings Dialog called End Surfaces: Override using Adjoining Walls. If it is checked the edge of the Wall will use the surface of the Adjoining Wall, even if it is the stronger Building Material. Check the attached image for explanation.

Re: In AC17, can walls clean up to roofs as well as to slabs

Anonymous — Mon, 23 Jun 2014 12:19:03 GMT

Everything is as you described:
I extended the profile down to the concrete intersection between wall and roof.
Roof and wall stop exactly where the profile starts.
Still not working.

Re: In AC17, can walls clean up to roofs as well as to slabs

Laszlo Nagy — Mon, 23 Jun 2014 12:30:45 GMT

This should work. Check the attached image of a Wall-Beam joint.
You can see where the Beam starts vertically because all its skin separator lines are black. However, the skin fills nicely merge and there is no line. Make sure the same Fills are used in the Beam and the Wall.
Probably the Beam and Wall geometry does not meet properly, there may be a bit of gap or overlap. Zoom in very close then you should see.