Problem With Hip Rafter On Hip Roof - 2009

[myBIMhero]

I am trying to create a basic hip roof. We want the hip rafter to cross over the intersection of our structural grid system so that columns and trusses can pick up the load. When I setup the eaves to align, then I miss the intersection of the structural grids. We did a pathegreon calculation to figure out the slope. The problem is that A) it is slightly off and I know Revit can be exacting in its math and B) if anything changes, we have to recalculate the slope. Is there a way to dictate exactly where you want your hip rafter to be? Please see attached file. Thanks. RAC 2009

[patricks]

I think you need to adjust your structural grids to where the hip rafter intersection is, instead of vice versa.

If you intend to build the roof with the different slopes as you have modeled, the hip rafter intersection is going to be dictated by those slopes. If the slopes change, the hip rafter intersection may or may not change.

If you try to build it with the hip intersection in a specific location, then the roof slopes will become some arbitrary number and nothing exact, unless you do the same slope on all sides of the roof. If that is the case, the hip rafter will always be at a 45-deg. angle to the eave lines, no matter what slope you use.

[trombe]

I am trying to create a basic hip roof. We want the hip rafter to cross over the intersection of our structural grid system so that columns and trusses can pick up the load. When I setup the eaves to align, then I miss the intersection of the structural grids. We did a pathegreon calculation to figure out the slope. The problem is that A) it is slightly off and I know Revit can be exacting in its math and B) if anything changes, we have to recalculate the slope. Is there a way to dictate exactly where you want your hip rafter to be? Please see attached file. Thanks. RAC 2009

Hi,
With walls align locked to grid , hip remains locked to grid, soffitt remains as original width created. When either side or end wall grid is moved, (smaller / larger) wall moves with grid, hip moves also.
What is critical ? soffit width or roof angle I am probably missing something, why is roof angle important when you seem mainly interested in hip position relative to grid ?
thanks
trombe

[myBIMhero]

Sorry - I never recived notification on this thread (I may be posting them wrong). The most important aspect is that the hip rafter runs from the center of the roof through the grid intersection to to the corner of the roof. Roof anlge is to a certain degree adjustable. The problem seems that you cannot dictate roof shape and it will in turn give you slope. We did find a solution using a flat roof and giving it points and split lines. This gave us exactly what we wanted - but now we cannot create a square cut edge - it defaults to plumb cut. So I am back to searching for my original answer. Thanks.

[patricks]

I looked at your attached Revit file again. I think for construction purposes what you have there is just fine. The distance from the top of the hip to the actual grid intersection is less than 1.5", the width of 2x framing.

If you dimension your grids, your eave overhangs, and give the height at the center peak of the roof, any truss manufacturer can make the trusses with the required slope. Even with stick-framed rafters it would work, since a stick-framed roof starts with the ridge beam and works outwards to the walls.

Any competent carpenter can figure this stuff out. I wouldn't worry about being 100% spot-on exact.

But to answer your original question - no you cannot have the roof slop driven by peak/valley/hip locations, unless you use the slab editing tools as you have already tried. Unfortunately as you have seen, options are limited when going that route. I think you'll just have to model the roof by footprint and run calcs to get the hip in the right place.

[Taans]

I am trying to create a basic hip roof. We want the hip rafter to cross over the intersection of our structural grid system so that columns and trusses can pick up the load. When I setup the eaves to align, then I miss the intersection of the structural grids. We did a pathegreon calculation to figure out the slope. The problem is that A) it is slightly off and I know Revit can be exacting in its math and B) if anything changes, we have to recalculate the slope. Is there a way to dictate exactly where you want your hip rafter to be? Please see attached file. Thanks. RAC 2009

I think you may want to creat a family that works as a roof. In the family, you make some parameter with fomulars to control the pitch (by using ref lines) and voids to make the hip always goes through the intersection of structural grid.

[myBIMhero]

YES!! That is an awesome idea. I will try to work it out. Thanks so much.

[dhurtubise]

You could use a simple annotation family to get the calculation right then use a slope arrow to keep workingwith a roof.