Possible to create a roof with two sloped layers?

[g_vandeel]

For a renovation project for a very big structural hal, i'm looking for a fairly simple solution. 

The existing metal roof sheets do'nt have enough sloping according to the current and future regulations. 
Our solution is to add sloped insulation sheets on top of it. 

At this stage i'm unable to create a roof (or floor) like this; see this exaggerated image below;

any help is welcome, thanks in advance

[vitorbortoncello]

add a layer and make it variable:

set roof slope to zero and work the slope with shape editing

[g_vandeel]

Hi Vitor, 
Obviously I did that allready. But that makes my bottom side of the roof flat. 
As you can see in the sketch, the bottom layer needs a slope, say 5mm/m (not variable)
And the top layer needs a slope, say 10mm/m wich is variable in thickness.

[Simon_Weel]

Doesn't seem to work OOTB. I think you have to use a Void to shave off the tapered end...

[vitorbortoncello]

in that case i believe it requires modelling the two of them separately

[g_vandeel]

yeah, i'm afraid so