Curbless shower in concrete-less/slab-less slab home
Confuzed
| Posted in Green Building Techniques on
I really like the idea of a concreteless slab (two layers of OSB over insulation over a vapor barrier and compacted gravel). However I am curious how I might implement a curbless shower.
Cutting the subfloor and removing a few inches of insulation and dropping your cutout piece back in seems the straightforward way… but then you have this disconnected chunk of subfloor just floating there.
On a framed floor its tied in with the existing joists, so it cannot move independently and cause cracks to form. Would that not be worth worrying about?
Anyone done this?
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I am all for slabless slabs (https://www.greenbuildingadvisor.com/article/minimizing-concrete-in-a-slab-on-grade-home) but they aren't the answer for every project. If a recessed shower is a priority, I would at minimum provide a concrete floor in that area, and it would need to be well-tied into the adjacent flooring. Tiles and waterproofing systems are not forgiving of movement.
Yeah... I know that concreate has its place. But the wife wants the softness that comes from a wood floor, but I don't really want to spend the money for a conditioned crawlspace if a slabless slab would accomplish the same thing (though I haven't completely eliminated the possibility so we can use it for mechanicals too).
I considered doing concrete in some places (bathroom, utility, laundry) where I would want a floor drain. Perhaps even under a small one under the kitchen sink/dishwasher. This would protect from perhaps the scariest part of a slabless slab... the house becoming a swimming pool.
I would think you still want full thickness insulation under the shower.
So I would drop the whole thing -- gravel, insulation and underlayment. I'd surround the dropped area with piece of treated 2x on edge, the same height as the amount of drop. I would screw the underlayment to the 2x in both the dropped section and the regular section.
If it was a big area I'd consider treated 2x4 joists under the dropped area.
The hardest part of dropping it into the gravel is that the gravel will inevitably fall into your hole creating a soft spot at the worst possible place... so the only choice would be to compact a pad for under the shower, apply a frame, then fill and compact the surrounding area.
But screwing the subfloor to the frame would ensure that the two pieces don't move independently and cause cracks/leaks.
I was really hoping someone had a similar detail that could be cut in after the subfloor is down.
With a poured concrete floor it's common to box out a "catbox" (that may be a regional term) with 2x lumber around where the shower drain goes and not pour the floor there. Then once the interior walls are up you figure out exactly where the drain needs to go, finish the plumbing and pour bagged concrete to fill the hole.
You could basically do the same thing with a concrete-less slab. Then it's your choice whether the floor of the shower is concrete or concrete-less.
Yeah... I think that is probably the best way. As I mentioned further up, might even do that to entire rooms so I can have emergency drains. Goal is to build a low maintenance home, don't want floods to ever be an issue.