Roof ridge not centered

[noah]

I'm beating my head against the keyboard on this one. I have a roof who's ridge is not centered on the house. See attached.

In roof edit mode I made sure that the total dimension is exactly 4' wider than the wall to wall dimension (2' overhang on both sides). 19' 8-1/2" from roof edge to centerline. The other side is exactly the same.

But after I finish the sketch the roof ridge is 19/32" off from the centerline that I dimensioned to.

Any thoughts? Is there a way to align the ridge.

Eaves are aligned. Roof pitches are both 9:12. Roof is sketched with lines (not by wall) because doing that wouldn't even allow me to create the roof for some reason. What am I missing.

Thanks!

[beegee]

All I can think of at the moment is that there may have been some rounding error that caused this.

Go to setting - Project Units and set the length rounding to the minimum ( 1/256" ) and then recheck your dimensions.

You could also try using an "EQ" constraint on the two roof edges.

[aggockel50321]

Also, while in sketch mode, select each slope defining line, go to properties, and see if each has the same "offset from roof base" value.

If they differ the whole roof will cant.

[patricks]

I have run into this problem several times myself. It happens when you have a roof that's defined by walls of different thicknesses, or if one side is defined by a wall with a set overhang, and the other side is merely a sketched line drawn a certain distance away from the wall. This can also throw off eave heights, depending on if the roof is set to truss type or rafter type.

What you may end up having to do is just sketch the whole thing, and not have any of it defined by picked walls. That will definitely put the ridge in the exact center, all the time.

[noah]

I do have walls with 2 different thicknesses. I suspected that was the problem and I'm pretty sure that I sketched all the roof lines but I'll check tomorrow to make sure. Thanks for the assistance. Despite the high cost of Revit, the help found at this forum makes it feel like it's free!

[Scott D Davis]

Draw a section through your plan and roof, and see what's happening at each side wall. I did a quick section to demonstrate how "Pick Walls" and "sketch lines by picking" differs. HTH!

[noah]

I've tried everything offered here as a solution and nothing is working. Please Help!!!!!

I'm attaching the latest image. What I did was copy the walls into a new file just to start fresh and see what happens. The southern wall is existing and a different width than the other 3 which are new.

I first created a new roof using lines - not picking any walls and only in a rectangle shape - ridge running east west. I aligned the north south roof edges with my reference lines + 2'-0" (not the walls). Ridge aligned with my centerline perfectly.

Then I tried to add the other ridge going north south. I edited the roof and trimmed up the lines. I didn't change any of the lines from the original rectangular roof. East west ridge no longer aligns with my center line! This is driving me crazy.

All eaves are aligned
Offset from roof base is 0
All lines are perpendicular
All lines are sketched not "pick walls"
units set to 1/256"

As far as I can tell the roof should have no relationship to the walls at the moment - only the grid lines that I drew. But it still cants to one side.

Please help - this is critical. 19/32" may seem small but this isn't acceptable.

[Max Lloyd]

It seems to me that on the example you have given, that the dimension is not accurate on the top left of the image. Perhaps you are picking dims to core boundaries, not wall faces? Maybe that will cure it.

[Max Lloyd]

And just out of interest, are the walls stacked walls? I have had all sorts of funny things happen with those.

[noah]

Thanks max but I don't think you're following. The roof is not associated with the walls at all. In fact, I just went into my example and deleted the walls and it still has the problem. This is just a roof sketched with lines. A basic rectangle works fine. Once I add the perpendicular ridge running north south it fails.

[noah]

One more try.

1. I started with a fresh template (default residential).

2. I drew three grid lines.

3. I created a roof by lines (NO WALLS - sorry). Drew a rectangle snapping to the grid lines.

4. Split the south face in 2. Added the extra geometry for the north/south roof.

5. Trimmed everything, set my slope angles (east/west roof is 9:12, north south is 6:12).

6. Finished sketch.

Ridge doesn't line up with center grid line!!!!!!!!

I'm convinced that there is nothing I'm doing wrong here. Can't I create 2 intersecting roofs like this with one set of lines? I really don't want to do two separate roofs because I tried that and since the roof pitches are different from one roof to the next I had trouble getting the valleys to clean up.

[noah]

So I tried to create the same roof but with the same pitch on every plane and it works fine. So that tells me the problem is that the east/west roof is 9:12 and when I try to add a north/south wall that is anything other than 9:12 it fails. This is horrible. Is revit trying to tell me that it's impossible to build a roof with 2 different pitches?

[bclarch]

Could you post the file?

[aggockel50321]

I confirmed what you did, Noah.

Not sure what's going on, maybe a bug.

Notice what happens to the ridge offset when you substitute in a thicker roof. It grows larger.

I was able to align the ridge by dropping the north slope defining line's offset from base a bit, but that's really not a fix.

Call the factory. (got the same result in 6.1)

[noah]

Attaching the file.

I can't believe that nobody else has had this issue before. Isn't this a very common roof scenario. Are people just living with the difference between ridge and centerline???

Thanks!

[tamas]

See attached images for explanation. See also the rvt file.

If you sketch your roof as one, the fascia heights will be kept the same.
If you made the roof as two roofs, all is symmetric as you want, but the fascias have different heights due to the different roof slopes.

I am not sure if this is documented or desired. Will ask John (who developed the current roof algorithm).

John's explanation: (I better put this here to avoid further misunderstandings)

Revit ensures that the fascia heights will be the same (along any slope-defining chain), but it does not do so by changing the slopes of any roof face. Besides the “constant fascia height” condition, we also impose the condition that the top faces of the roof meet “smoothly” at the fascia edges (unlike in the two-roof example). Given that this roof uses varying slopes, these two conditions force the upper eave lines of the roof on the north and south sides to be at different heights (as you can check in the Revit model), and this in turn causes the east-west ridgeline to be off-center. The slopes are all exactly as specified in the footprint sketch, however.

[noah]

thanks tamas. It's nice to know I'm not crazy. Let me know what you find but I think the two roof scenario is all I can do for now. But I need a tutorial on how to get the valley's to clean up with two different roof pitches. The 6:12 (north/south) will actually be overframed the 9:12 (east/west) so this is probably a little more accurate way of doing things. I assume I can just align the facias in elevation view after I make them.

[Scott D Davis]

So, in actual construction, the roof could not be made with identical slopes, and matching eave lines, and the top edges of the roof 'meeting smoothly' without shifting the ridge of the roof.

By the top two edges 'meeting smoothly' I assume you mean that both ridges will be at identical elevation? And for the roof that Noah is trying to create, one ridge must be slightly higher than ther other?

[tamas]

So, in actual construction, the roof could not be made with identical slopes, and matching eave lines, and the top edges of the roof 'meeting smoothly' without shifting the ridge of the roof.

By the top two edges 'meeting smoothly' I assume you mean that both ridges will be at identical elevation? And for the roof that Noah is trying to create, one ridge must be slightly higher than ther other?

No, I think what he (John) meant is that the roof edges at the top of the fascias are kept "smoothly" together. Look at the rvt model I posted and notice that the bottom edge of the roof was cut by a horizontal plane to make the fascia the right height while the top edges of the fascias at the valley are at the same height.

[aggockel50321]

And for the roof that Noah is trying to create, one ridge must be slightly higher than ther other?
I think you've hit the problem, Scott.

Remember the ol' saying, "Roofs grow up" and "Floors grow down", coined, I think, by Steve St., formerly of that great state on the Right coast.

For some reason, when you try to construct the roof that Noah has proposed, the joined side (in Noah's example the south side), compensates the roof face's slope in order to maintain identical eve heights.

Given that the eve face of a 9" roof will be greater than the eve face of a 6" roof, the algorithem compensates for this by aligning them and then changes (silightly) the slope of the adjoining main roof face to compensate for the difference, & thus, the offset ridge.

I got a feeling a better solution would be a warning that the eves have to be adjusted to hold the main roof's symetrical integrity, and then let the user decide.

These poor developers must go nuts trying to figure out every outcome of what at the time seemed a simple decision!

[tamas]

No, not quite. The slopes are exactly as set in the sketch. The algorithm compensates by changing eave heights and adding rafter cuts.

I edited my original post (on the previous page) and added more images to better explain what is going on. Please read it again.

Sorry for the incorrect first message (about changing slopes).

Tamas

PS: Just imagine what we had to go through to get wall joins as "good" as they are now. ;-)

[beegee]

Thanks Tamas,

Those images really help to understand what is going on.

[Max Lloyd]

I'm so confused. Seems simple to me?????

Ok, perhaps not. Just realised what all the fuss is about. Same problem here, makes no sense at all.

Good point!!! Can't believe I had never noticed it!

[Max Lloyd]

strike that last thought. I am confused. Same scenario, this time sketching the roof with an offset to walls (300mm) and the main roof being steeper than the smaller roof. Check out the results this time. Ridge is fine, but valley is all messed up. Always thought it was odd that revit calculates the eaves height from the inside of the roof instead of the outside. Makes for some odd geometry.

Strange, its all too late for me. Off to bed, come back tomorrow with a clear head! (too much beer, nice meal though) night night all.

[Scott M.]

Revit is showing the vally's correct in the way that it was drawn. To get the vally's to the inside corner were the fascia of the lower pitched roof and the main roof you must extend the soffit overhang of the lower roof to have the same fascia width of the main roof. The align eves tool works great for this purpose.

Scott M.