On Fri, 21 Aug 2009 02:48:06 -0700 (PDT), Arthur 51
wrote:

If you want to make it look pretty with filler, that's up to you.

I intended to strengthen the joint with 3 or 4 screws as well as
'glueing'.
The filler option seems right in order to gap fill to prevent water
getting inside the joint to undermine it.

OK, so you're asking about filling, not gluing.

The general rule is that it's better to provide drainage than attempt
sealing.