Seeking Help on Creating a Flat Roof with sloped drainage and uniformly thick sheathing on top


I have looked through the forums to find an answer for this, but as of yet, had no success. I am trying develop a better method of flat roof (membrane/plywood over sloped insulation) modeling and would welcome any advice users might have. I currently use the method of cutting a thick insulation roof with an in-place void family. This achieves a good result in plan but does not include the sheathing layer in section. Alternatively, I can manipulate a multi-layer assembly of insulation and sheathing (insulation thickness variable), but that generates undesirable linework in plan that I would like to avoid.

Has anyone tackled this before? I am still new to dynamo and attempted a solution using clockwork nodes, but no luck. Thank you for all of your help!

This wont help you accomplish it with Dynamo, but: There are ways to model it with Shape Editing (the multi-layer variable thickness insulation middle) you are describing, that can avoid the additional linework in Plan. You have to use a subtractive method of modeling the roof oversize as uniform sheets, and then simply cutting it away with vertical openings. Its quite fast to do, and the slopes are all perfect, and there is no unwanted linework.

But its a bit backwards in thinking. Its a bit more like grading a site, than designing a roof, haha.

Thank you for you help on this Aaron. I think I may understand the method you are describing, but a few questions. In this process, are you using separate oversized layers for the insulation and for the sheathing? Also, will the sloped sheathing hatch in the final result run parallel to the slope of the roof, or will it appear as the default orientation of the material (cut) hatch?

My issue with multi layer editing, is that I have always subtracted out an inverted pyramid (a blend void representing the drainage area), but it cuts through the top sheathing layer that I would like to keep as continuous. Would love to discover I’ve been doing it wrong and a better approach exists! Thank you again.

I believe that this is the sort of setup which @Aaron_Maller is describing.

Yes and no. You cant get accurate with just the points, even if you do the math. Revit will put in triangulation lines, and not release them unless you flatten the roof. Here, let me make a quick video.

Great point! I wasn’t intending to show the whole workflow, more that by ‘adjusting the modifier elements’ you update the thickness in section - no need for a void family and everything is parametric.


Looking forward to any overall documentation you have. Note that my personal preference was always to modify the slab programmatically with Dynamo (but admittedly, I have a problem).

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So, im super embarrassed. I said i was going to make a video… And then forgot. So i made it today. Its a quick and dirty video, so the sample building is tiny. Why does that matter? When you use the same technique on a real sized building, it tends towork out very well with the steel elevations, as well. Because this entire building is smaller than my house, it looks silly.