Query the height of a single face

[TeodoraCristea]

Hi,

is it possible to find out the length of a single edge or the height of a face? 

My model looks like this:

Now what I want to do is find a way to generate the door on the side of the model that is closest to the ground. I read on another post that it isn't possible to make terrain queries. But is it somehow possible to find out the height of a face and then generate the door on that side? Since this is just a shed, modeling stairs for it isn't an alternative.

Thanks,

Teodora