Sealing a shower

I have a shower cubicle, about seven years old, lined with laminated waterproof boards instead of tiles. The joins between boards are metal joining strips, and the joins with the shower door are sealed with sealant, now deteriorating.
The shower tray has upstands on all four sides, and the door unit and boards are installed inside the upstands. Condensation on the outside of the shower door can drain into the upstand on the outside; the same may be true of the back of the wall boards.
I have some water penetration evident in the plasterboard wall to the side of the shower door (outside) which could be either water leaking through the sealant between board and door above the level of the upstand, or wicking/overspilling of water collecting inside the upstand on the back of the waterproof board. There is some evidence of sealant, dust and rubbish inside the upstand that could block free drainage around it.
My question is, should the bottom of the wall boards and shower door be sealed with sealant, or should they be left open so that any water contained by the upstands can drain under the board/door back into the shower tray? Are the edges of these waterproof boards equally waterproof?
There is old sealant there at present, but I am tempted to remove it, re-seal the join between door and wall boards, but leave the bottom edges unsealed and relay on the upstands to contain water at that level.
Chris R
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On 03/10/2010 14:51, Chris R wrote:

Something to consider, I had a leak with water leaking into the space under the shower. It took me some time to work out that the grout was a bit 'thin' and missing in places, and the water was entering here and running down the back of the tiles. But as you have boards and no tiles, probably this does not apply
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Indeed.
I have now raked out all the sealant and it was wet and blackened with mould on the back (ie in the hidden space between sealant and upstand) all the way round. I am inclined to leave the bottom of the boards unsealed unless someone tells me otherwise. It will leave a slightly unsightly gap, though. I'll replace the sealant in the corners, which I strongly suspect was leaking. There was no sealant under the shower door.
Chris R
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