[james67]

i doubt the foam will absorb water like you suggest. GS is a closed cell foam and in my experience sheds water rather than absorbing it. i suspect that the water is only going to drip through in areas where the foam didnt meet during expansion.

james

 

[james67]

a few things...

the wood, treated with stain WILL mold or rot. you need to get marine grade epoxy and coat the surfaces OR cover them with panes of glass or acrylic.

there are options for growing mediums available in sheets. one such item that is pretty commonly available is cocotek which you can get through your local hydroponics store.
youll still need to seal the wood before siliconing it in place

james