Flat roofing

[PeterJ]

What do you people think are the best ways of implementing a flat roof in a model?

No flat roof is flat - or at least that is true here - so do you set it to the 1.5 degree pitch? If you do that and you have a flat structure below with firrings or perhaps cut-to-fall insulation to tilt the deck and finish then that doesn't quite work.

I have done double skin flat roofs, with a tilted deck and finish and a flat timber structure only below, then made up the difference with drafted information but I'm interested in what the rest of you are doing.

P

[sbrown]

Typically in our flat roofs we do slope the structure, it is cheaper than adding tapered insulation. So I model it that way with a 1/4" slope on the roof and then use my roof based bar joists underneath that, the roof itself consists of the deck and 3" rigid and then the membrane. Then I just add crickets as detail lines in the roof plan or model them only if I need to know if they will work.

[Steve_Stafford]

Repost from alt.cad.revit of an explanation of structural sections to "slope" steel. Chances are you don't need to model steel for your building completely, only areas where you actually create views that see or cut the steel. So...placing it in key location might suffice. Steve's explanation, I found helpful, since I didn't know about it at the time.

In the Structural Design Bar, use the Framing Elevation tool to place a framing elevation which, by design, associates itself to a column grid (this assumes you have placed your columns along a column grid - if not you'll need to place a grid before continuing).

Once the elevation is placed, open the newly created elevation view. In this view you can now place your beam at any desired angle, snapping to the tops of the columns as you like.

The Framing elevation is fundamentally different from standard grids in that it has a plane defined (the grid) on which elements can be placed.

--
Regards,

Steve Burri
Autodesk, Inc.
Client Support Manager - Revit

[PeterJ]

Typically in our flat roofs we do slope the structure, it is cheaper than adding tapered insulation. So I model it that way with a 1/4" slope on the roof and then use my roof based bar joists underneath that, the roof itself consists of the deck and 3" rigid and then the membrane. Then I just add crickets as detail lines in the roof plan or model them only if I need to know if they will work.

crickets?

In the above instance you are using a steel structure with, I imagine, a suspended ceiling. How do you do it for timber structures, where you may tack plasterboard to the u/s of the timber and so require it horizontal, or perhaps for precast concrete slabs, which may be battened out below but are still generally laid flat?