Why is it not possible to choose a reference level for roofs with the same options as slab reference ?
(Bottom, bottom of structural part, top of structural part and top.)
Usually, a tile covered roof is defined by the top surface of it's structural frame. It means that if I change the composite (e.g. replace the top : ceramic tiles by slates or replace the bottom: 10 cm bottom isulation by 25 cm bottom insulation) this structural part of the roof should remain at the same level.
The current parameter doesn't give this possibility. So after changing a roof composite, we need to moove it up or down.
Please solve it with the 4 level options that already exist for slabs.