Building Material Override?

[toman311]

Hey all,

For some reason my building materials aren't interacting right. The priority levels are set right within the Building Materials dialog box, but when I use the "Trim Elements to Roof/Shell," the walls being trimmed to the roof show their outline on the top portion of the roof. They are trimmed right, but the wall stud building material texture is different than the roof sheathing material texture, so it doesn't look right in 3D. It trimmed right when I started the model, then somewhere along the way something changed. It's like the building material priorities have been overriden.

I checked the Renovation Filter options to make sure they didn't have the, "Do not Intersect," option selected.
I checked to make sure that the Layer Priority Numbers were set to the same number.

I'm not really sure where else to look. I'm clueless. I checked everywhere. Maybe I missed something that I've already checked. Does anyone have any ideas?

[Barry Kelly]

Carefully check the strengths of the building materials used in the walls and roof.
Stronger building materials will cut the weaker ones.
Your walls must be stronger than the roof.

Barry.

[Anonymous]

Yes. To better check it, select the Roofs and the Walls and open the Building Material Settings Dialog. You will see the all the related BMs are highlighted. You can then compare them.
Hope this helps.

[toman311]

Yes, it is the Building Material settings, but for some reason if I change the wall to another wall it goes away.
This confuses me. I don't know if anyone knows why this is. I'll try to explain.

I have a wall with made of Gyp. Bd. / Wood Framing / Plywood Sheathing / Siding. When I change the wall to another type made of Siding / Plywood Sheathing / Wood Framing / Plywood Sheathing / Siding , it behaves differently. The roof is made up of Plywood Sheathing / T&G Boards / Wood Framing.
On the wall with the Gyp. Bd., the Plywood Sheathing shows on the roof, but the top layer on the roof is made of Plywood Sheathing, so, really, the walls Plywood Sheathing doesn't show up. When the wall gets changed to the Siding on both sides, The Wood Framing building material shows up on the roof. The Wood Framing building material is made of a different wood texture than the Plywood Sheathing on the roof, so the problem shows itself. That's what is seen in the screenshot I took and shared in this post earlier.

I'm not sure why the Wood Framing building material shows through because the priority is lower than the plywood sheathing. My guess is that any building material between stronger building materials takes on the stronger building materials priority number.

Is this an accurate assumption?

[Anonymous]

Hi Toman311,
It looks like you are using the same Plywood BM on the wall and roof.
You'll have to duplicate the Plywood BM, name it lets say: Plywood_Roof, and give it a stronger priority.
You should also change the original Plywood BM to something like: Plywood_Wall.

[Barry Kelly · Accepted solution]

When you are using the same building materials in the roof and walls it can get a little tricky when you have lots of skins.
Like materials (the external cladding) will trim each other allowing the inner skins to extend.
When you use a wall that has weaker external skins and the roof ply is stronger, it will cover those up.
If the roof ply is stronger than the wall inner skins, it will trim those too.
If weaker the inner wall skins will show through.

It is a bit hard to explain.
You can see in the image attached I have a vertical wall and slabs - all the same composites.
I have shown these, as slabs and walls intersect automatically (no need to trim).
You can see especially with the top 2 slabs how the trimming changes just because one of the slabs passes through the entire wall.
Probably not a good example, but you can see how things can change.

It is all a bit tricky because generally you will want the core (inside) of the wall to be stronger and the external cladding to be weaker.
But when you use the same cladding on the wall and roof it can be a bit unpredictable.
As Brazza mentioned, it is better to have 2 claddings, one for wall and one for roof.
They can look the same but give the roof a slightly higher strength so it will always cut the wall cladding.


Another tip is to use Solid Element Operations on the walls/roof.
Subtract the roof from the wall with upward extrusion.
This will trim the roof to the underside of the roof regardless of material strengths and the walls will never show through.

Barry.

[toman311]

Thanks both of you for your responses.

I'll have to add a roof sheathing building material then.

Thanks again.

[Erwin Edel]

As a workaround / alternative method: what we do is model the ceiling finish of the sloped roof seperately. This way we can use simple solid element operation (which disregards building material priorities), since the bottom of the 'structural' part of the sloped roof will not be removed by anything anyway.

We actually need to specify this ceiling part differently from the roof part anyway, so it works out well enough.

So in short: instead of using 'connect', we just use the old-fashioned SEO method that existed even before building materials were introduced.

[Geof Gainer]

I've often wondered, what did the folks at Graphisoft have in mind when they assigned the various priorities to Plywood, Underlayment, Subflooring, Wood Sheathing, and OSB? Were there particular applications each was intended for? Aside from Subflooring it doesn't seem obvious which to use on exterior walls vs roofs for example. Plus, contractors I work with sometimes use the terms Underlayment and Sheathing interchangeably. 

[Erwin Edel]

In our template we generally have 'structural' and 'finish' versions of the same materials.

Some projects require some extra 'custom' variations.