Free IFC BIM Viewer

For a professional free BIM viewer (Building Information Modelling) that fits with the ethos of 'Open BIM' (utilising a range of software platforms and sharing data in 'IFC' format), try Tekla BIMsight:

http://www.teklabimsight.com/

Images from Severn Partnership

It is available to use on PC, Tablet computers and also as 'Tekla BIMsight note for ipad & iphone.  The 'note' version allows for information to be tagged on a model and easily shared with a mobile device to aid collaboration on BIM projects.

Tekla have a help centre and support forum, although most of the key tools for the full PC version are self explanatory (Clip planes, navigation, notes, layers & attributes).

Follow them at: @tekla

Link to Support Forum

Link to Download