residential roofs

[thomasf]

I've looked all over the internet and the forums here, but have not found an answer to this question.

Is there a tutorial anywhere that explains how to create a residential roof with varying pitches?

Everything I have come across, even examples of complex roofs, use the same pitch all the way around, but in the real world most houses have one pitch side to side and a different pitch front to back.

I have a roof that has a 12:12 side to side pitch and a 7:12 front to back pitch. I know from years of experience that using the standard construction methods here in Texas that a 12:12 pitch has a 1'-0" overhang and that a 7:12 pitch has a +/- 1'-8" overhang.

However, even using the align eaves command, Revit gives me an overhang in excess of 2'-1" for the 7:12 pitch and, even though I had the "Extend into Wall" box checked the roof did not intersect the inside face of the stud as it should.

Is there a tutorial out there for this type of roof? Any tips/tricks I should be aware of?

Any assistance would be greatly appreciated!!

Tom

[johnf.77896]

Tom could you post an example of what you are attempting?

[thomasf]

All I have is a pdf file of the entire project, but it is over 7Mb. I'm not sure if I can post something that big here.

[thomasf]

OK, I used my snipping tool to grab just the roof plan.

As you can see, in one direction the pitch is 12:12 and in the perpendicular direction it is 7:12.

Capture.JPG

[sbrown]

You can use slope arrows and make multiple roof slopes, for complex roofs like this don't fell like you have to do it all in one sketch.

[thomasf]

If I use slope arrows don't I need to know the height at the tail of the arrow or at the head? I've only done simple roofs with the same pitch on both sides, anything beyond that is a bit over my head. That's why I was hoping to find a tutorial or some step by step instructions. I've got a lot of the pieces done, although the over hangs are close they are not correct, but I still can't get some of the roofs to join together.

[Alfredo Medina]

There is another way to do complex roofs, that is overlooked. In brief words is this: In the conceptual design environment, draw the floor plan of the roof, as shown in your image, using reference lines. Then create reference planes in elevation. Of course you need to know the elevation of the ridges in advance. Then, create faces, then lift the points to the correspondent reference plane and elevation. Then, load into project and apply roof by face.

[patricks]

Yeah I would do a couple of main roof forms and then add various projections as necessary using the Join Roof tool, and possibly some vertical or dormer openings if needed.

As for the slopes and overhangs, it depends on how it will be built, i.e. placement of rafters on wall top plate, eave condition (aligned, not aligned), etc.

If you build a roof with 12/12 slope on two sides, rafters extending out 12" past the brick/siding, and the bottom edge of the rafters (bird's mouth cut) aligned with the top inside edge of the wall top plate, then the 7/12 rafters could end up extending out more or less depending on how the rafter ends are detailed. The 7/12 rafters' bird's mouth cut would also have to be different than the 12/12, or the 12/12 rafters may need additional blocking above the wall top plate (or taller walls).

I just made a roof as described, with 12" overhangs on the 12/12 slope and 20" overhangs on the 7/12 slope. The roof is set to Rafter and Plumb Cut. After aligning eaves (using Adjust Plate Height) and adjusting the roof height so that the 7/12 rafter bottom edges aligns with the inside wall top plate, I see that the 12/12 rafters would need 3 1/4" additional height to get to the bottom of those rafters. Also the 12/12 rafters would need more trimming on the bottom to get an equal soffit height all around.

Examine the attached file to see what I mean.

*edit* You could make it so that the bottom of the rafters sits on the wall top plate all around, but then the eaves would not align. The eaves of the 7/12 roof would slope down at each end to mate up with the 12/12 eave end, which I have seen some houses built that way. Though I think that detail looks pretty weird. It makes me think they just couldn't work out the roof right and just "fudged" it to make it work.

[thomasf]

The only problem is, if you look at your roof in section, one of the pitches is plating correctly, from the inside face of the stud wall (see section 2), but the other pitch is not. But, I just remembered the math and it is very simple actually. The overhang is the run (12") divided by the rise (x) times 12 = overhang in inches.

so for a 12:12 pitch it's 12/12 = 1 x 12 = 12"

7:12 would be 12/7 = 1.714285714285714 x 12 = 20.57142857142857"

this is from outside face of stud, not face of finish material. So, i'm going to try using this overhang measurement & see if it works.