Angled Roof - How do I construct a skillion roof w/ 2 angles

[Anonymous]

With the roof tool how do I construct a skillion roof with two angles/pitches.

For example.
Select the roof tool,
Selected the simple skillion roof,
enter the first node of the roof pivot line,
then the second node (usually vertical or horizontal)
draw a simple square roof with a 6 degree pitch.

Now this is where it gets tricky.
If I move the roof pivot line to an angle I get a roof with two angles.

What I would like to know is how to work out where or what angle to place the roof pivot line to get a main roof pitch at 6 degrees and be at 10 degrees (in its side elevation)

Is there any geometry or simple way of working this out.

Thanks in advance.

Brendon

[Anonymous]

The second is again a plan view but rotating the roof pivot line.

(This is what I'm chasing, how to work out the rotation angle of the roof pivot line to achive a 15° pitch in one elevation and in the other elevation 30° pitch - see more attached images).

[Anonymous]

Elevation of roof with two pitches. Elevation 1

[Anonymous]

Second elevation perpendicular to the prevoius elevation

[Anonymous]

Final 3D view of want I'm chasing

[Thomas Holm]

I think we understood your goal, brendon. You've got four (I think)different methods proposed. Did you try them?

[Anonymous]

What you are looking for is tricky, and not just because of AC's level line method for defining roofs. It is inherently complicated to define a planar face of more than three points at an arbitrary angle. All the more so if you don't account for the roof thicknesses.

Following is the only way I know to do what you want accurately in ArchiCAD (short of a nasty experience with trigonometry and a calculator).

1. Make two roofs at the desired pitches (as you have already done). Make them zero thickness to eliminate height problems caused by the different pitches.

2. With the shallower roof selected, command/ctrl click to get the elevation of the roof at its high corner as shown (you can also get this from the "Z" coordinate in the 3D window) and copy the value to the clipboard.

3. Select the other roof and then use Design > Create Roof Level Lines. Paste the value copied above to get the line at the desired height.

4. Draw the final roof with the pitch reference line from the corner of the first roof to the intersection of the level line with the opposite wall as shown.

5. Elevate and adjust the pitch of the final roof as needed in 3D.

[Anonymous]

Thanks Mathew,

Thats exactly what I was looking for and it works.

Much easier then the other methods proposed (Thomas).

Thanks.

[Anonymous]

Ok.

It's not exactly correct/perfect, however this method is 98% there.
I would have liked to eliminated step 5 but will do.

[Barry Kelly]

brendon wrote:
Ok.

It's not exactly correct/perfect, however this method is 98% there.
I would have liked to eliminated step 5 but will do.

Draw the two roof planes at your various pitches with zero thickness as Matthew suggested.
Then select and view in 3D.
Now draw the real roof - you will be picking three points to define the roof slope.
The first point is the low corner where the 2 roofs start.
The second point is the high side of the first roof (15°).
The third point is the high side of the second roof (30°).
Now all that is left to do is define the shape of the roof plane - ie two diagonal points for the rectangular roof or more more the irregular polygon method.
Barry.

[Anonymous]

brendon wrote:
It's not exactly correct/perfect, however this method is 98% there. I would have liked to eliminated step 5 but will do.

To the contrary, it is precisely correct (at least within the limits of the floating point accuracy of the system). "Perfect" is more of a value judgment 😉

It seems step 5 can be skipped, along with steps 2 & 3, by using the method Barry suggests. I guess I'm too stuck in my old ways sometimes. I haven't drawn many roofs in 3D and didn't realize that you can set the pitch by the 3 point method. Thanks for the heads up Barry!