OpenStudio is modifying my SketchUp geometry

edit

I am new on OpenStudio so this may be a bit dumb :

I built my geometry with Sketchup, then loaded the .osm on Openstudio to work on Constructions, Schedules etc. but when I look at my geometry from the OpenStudio application viewer, it is modified : the pitched roof is now a new floor with a flat roof. And if I load it again on Sketchup the roof has really been modified into a strange mix of surfaces and lines.

I there a special trick to avoid this ?