Coating to waterproof inside of flood & drain table?

[ChaosCatalunya]

Okay Chaos thanks.

I think you hint at another great reason to look at sealants over liners. You can engineer sealed wood way more than you can engineer lined wood. For example, the way I build my tubs I have to do a tricky bit of cutting. First I build the tub. Then I take my bigger holesaw (slightly bigger than the fitting at its widest diameter) and cut down into the bottom of the tub, to about 3/8" deep. Then I switch out to my smaller holesaw (slightly bigger than the part of the fitting that has to go all the way through) and using the pilot hole from the first cut, I go all the way through the tub bottom. This way I can seat the fitting flush with the bottom of the tub so it drains better. The problem with this is it's kinda dicey and weakens the tub bottom around the fitting.

With a sealed tub I could do this a couple different ways. One way would be to just cut a square a couple inches bigger than I need for all my fittings, then screw a piece of ply to the bottom of the tub, over the square, and put my fittings through that. This way, if the screwed on piece rots, or gets damaged, or if for some reason I want to change the way my fittings are configured, I could just remove it and replace it with another without a lot of hassle.

Another good idea would be to put thin ply on top of the tub bottom to make gutters. This would be a lot harder with a liner because liners never just lie flat. They always wrinkle a bit. You could do all this stuff with liners but it would be much easier with sealants.

Spot on mate, not just copying something else, but really understanding what you need and how to do it.

Wood, like Liners, can cause issues, I always seal all mine with Varnish at least.