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Flat roof composites with a in built 1:75 fall /slope


Hi All,

For my projects it is necessary for flat roof build ups to have a sloped element above the timber roof deck to ferry the surface water to a trough gutter. Currently I create this by having two roof composites that together make the full flat roof build-up, the first being a totally flat timber deck with OSB and plasterboard the otherside, the second being the 1 degree sloped firring, insulation and EPDM finish.

I wondered if there was a way to create a roof composite to incorporate part of the element being on a sloped angle such that this could be one composite?

This would be useful to me because this would make flat roof skylights look cleaner as I will not need to create a second opening.


I have the same issue. I always have to split it. Set the skylight in to the flat element and then cut a hole in the sloped part. It would be good to be able to do this. 

Lee Hankins
ArchiCAD 4.5 - Archicad 27UKI Apple Silicon 5003
macOS Ventura (13.5.2)

Tim Ball

You could try using the opening tool to cut through both then add the rooflight as an object and complex profile beams to trim the opening inside 

Tim Ball

AC26, iMac

User since V5

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