If you haven't already got Caro's transparent floor, you can download it here.

In the following screenshots, it has been tinted so that you can see where it should be placed.
KVerandahRailWhiteNZ.iff
KVerandahFramedNZ.iff
KVerandahFramedMidNZ.iff
KVerandahDecoration.iff
KVerandahRoofBlueLeft.iff
KVerandahRoofBlue.iff
KVerandahRoofBlueRight.iff
KVerandahBlueOutwardCorner.iff KVerandahBlueInwardCorner.iff
Place the framed verandah piece.
Place it again
and turn it 180°.
Do the same for the decoration piece.
 
It's best to build the
upstairs verandahs first.
You will need to use Caro's
transparent floor tile.
Add another row to the
outside of the verandah.
Now you can place and
flip the verandah pieces.
To create a 'hanging' roof, you will need
to add more transparent tiles.
Adding a verandah decoration will
require extending the transparent
floor even further. Put a column
on the ground level to support the
extra tiles.
After you have added the
transparent floor ...
... delete the column, then
add the decoration around
the edge of the roof.
Now the ground floor can be worked on.
The Sims will walk straight through
the verandah railings. The careful
placement of plants can help
overcome this problem.
The Pieces and
their Filenames