Hi, Danny: You can try this: In detail edit ?C build shell, Create child underground wall to replace the purposed E-wall. But you have to know I ??m a NEW user, so, you know, be careful with this method. The model should be finish like below: you can see I replace the core of roof and a part of the top E-wall. You can find the calculation method in the Doe 2 help files : Volume 3: Topics > Envelope Components > UNDERGROUND-WALL and UNDERGROUND-FLOOr Hope it is helpfulJ Joey ??????: Danny Xu [mailto:danny_xu_chengyu at yahoo.com.au] ????????: 2011??10??12?? 5:27 ??????: equest-users at lists.onebuilding.org ????: [Equest-users] Modeling a semi-underground floor Hi all, Would you please advise how to model a floor in eQUEST with south and east walls underground and west and north walls above ground? Thanks. Regards, Danny