Consider model element properties
Vendor-specific recommendations
Autodesk Revit: Element properties
Within Revit there is a setting that makes elements such as walls ‘room bounding’. Elements that have this setting will affect the room volumes when exported via the format of choice, whether it is gbXML or IFC.
Image from Autodesk Revit: Properties dialogue – Room Bounding option
It is good practice at the outset of the model creation to choose which elements are going to be set as the primary ‘room bounding elements’, i.e. one floor/ceiling/roof element and one internal/external wall element. All other elements placed within the model can be included to show design intent, but have this setting unticked to avoid them interfering with the gbXML or IFC file exported from the BIM model. An example might be internal partitions creating cubicles in a toilet – setting these to non-room-bounding greatly simplifies the room geometry.
Images from Autodesk Revit: Wall thickened out (left) and wall with lower sill (right)
Modelling tips & Common Issues to look out for:
Room/Space separation lines should only be used to divide up open plan spaces. They should never be run along the same line as other solid partition or used to close off an area of a model to solve an issue with the Room/Space placement tool.
Image from Autodesk Revit: Wall with room separation line running along it
Where walls in a model protrude into the centre of a room or sit in the middle, the decision need to be made to either make these non-room bounding or to add in room separation lines to create separate spaces as indicated in the images below (yellow dotted lines).
Images from Autodesk Revit: Plan view highlighting walls protruding into a room (left) and partitions in the centre of a room
Graphisoft ArchiCAD: Element properties
The zone tool in ArchiCAD by default ignores elements such as columns. Care has to be taken if the ‘Zone Default Settings’ are edited. In addition, at the outset of the model creation, care has to be taken to choose which elements are going to be set as the primary ‘zone elements’, i.e. one floor / ceiling / roof element and one internal / external wall element and to keep the model as simple as possible.
