Extrude imported object or part of it!

Working on a basic 3d furniture configurator,
Trying to make something like this : http://monmeuble.mobibam.com/
I’m looking for the best way to resize my loaded file by extruding it ?

on my code I already found a way to scale the whole file but it’s only squeezing and enlarging when trying to resize (code: https://codepen.io/RedKizaru/pen/qyKbdg)

So, what is the best way to resize my loaded file by extruding it ?
is there any other way to do it properly ?

Can you explain in more detail what you mean by extrude? Perhaps some sketches would help.

Look at the example of mobibam( first link)… i’m trying to reproduce something that can do the same thing

for now i can resize the file but it’s just squeezed when I minimize the size and enlarging when I try to make it bigger

so I’d like to use some sort of THREE functionality to extrude the file (adding little parts) when maximizing size
3d-extrude … and vice versa