Yes, the leaves will sink down, so you should really heap up the first load; dampen them as they put down and walk across them to pack down, as the leaves are spread. Afterwards, you add more leaves as a mulch every year, so it will pretty much maintain depth. I found about 15-25% shrinkage which is considerably less than for lasagna-style, maybe because of being packed down?? Sure, broken pavers (2"-3") will do for drainage, but if some are in good shape, think about setting them at the top edge every few feet to have a place to sit. You may need to get some gravel as well, it takes a surprising amount to fill 4"x48". Consider laying soaker hose as part of the finish work. Attached to a repeating timer, it can do the watering for you. You should find that a bed with organic compost is better at managing water than plain dirt. That is actually a reasonable amount of light, a good many annuals and soft perennials would be happy with it, as well as many of the 'shade' lovers. With that light, I'd be tempted to get involved with fibrous begonias. No, no I mustn't think about that, it's YOUR bed. Thisle ~ you'd be better off posting a separate thread. Just which plants are in the bed will matter (along with how much time and energy you have). Most shrubby types will do fine if you pile the leaves to about 4", but those perennials with soft crowns will be happier to be lifted and re-planted this fall so that their crown can stay near ground level. I practice a mild form of lasagna around my perennials, giving them a couple inches of shredded leaves in the fall, then in the spring I top that with a layer of paper and another inch or two of the leaves. By doing this every year, the bottom consistently gradually turns into compost while the top [fresh layer] acts as a weed barrier.

All-weather Duct Tape. I use it every winter to seal one of my GH doors shut and prevent drafts. Then just peel it off in the spring. The "all weather" type sticks even in the cold and wet weather.

Thx yes was going look around the control valve next. Looks to me that the tile has not been routinely maintained (sealed). So some aging and cracking in grout may have added to the problem. Been in the house two years with no visible issues with daily use, it looked perfect (e.g. no staining in bottom grout until suddenly now). This disscussion really makes me wonder about the way tubs are sealed to walls. A Silicon seal acting like a ~1/4" water dike trapping and holding water makes no sense. Seems to me that there should be a 1/2" gap under the wall backboard with current recommended water barrier behind extended 1/4" further overlapping the tub flange. And their should be engineered a flexible polymer strip to be inserted in the gap to seal between the tub ledge and the tile. It should have antimicrobials in it and be treated annually with an application of antimicrobial treatment. The invention could be a firm microbubble nondegradable polymer. And it should have a GoreTex film like property, where free water can't get across it, very little moisture is held so it dries quickly, and moisture settling behind the bottom tile can excape as water vapor. Slight permeability to the flexible material and a fused backing of the Goretex oriented towards the flange wall could accomplish this. It could have a thin flap on the back topside so it is installed along with the bottom tile and act as the standard 1/8" spacer below the bottom tile. Being flexible and supported from the back edge it could flex downward if the tub ledge moves downward when weight loaded, still helping block water entry. If the tub settles a little permanently, the permeable membrane would still help block transport water out of the gap. A spongy expandable sealed bubble like strip material would allow the most water blockage with flexing and also be best at preventing any air gap developing. Just an idea ... on my wish list.

Ceiling joist is parallel to the wall and the range is not on an outside wall, the side entrance stairs are right behind it