family for concrete tapered beam with nib (top of beam is level, only bottom varies)?

[garyn.189301]

I'll appreciate if any one can assist me with this family, using RST 2010.

[arch_kashif]

I'll appreciate if any one can assist me with this family, using RST 2010.

One way of doing that would be to open Concrete Beam family, save as a new family e.g. "tapered beam" and add a tapered void element on one of the side elevations of the straight rectangular beam. If you master parametric geometry construction you can buildin family type parameters to change tapers angle/length, otherwise just create the taper you require in the family.