Current subfloor is hardwood T&G floorboards on 90x45 joists, but intention is to cut this out flush to wall plate and replace with 19mm fibre cement duraboard.
Reasons being:
- there is currently no flooring under the built in bath (new one will be freestanding)
- there is a hump from joist end pushing up in middle of room (I intend to plane this down to level when floorboards removed)
- I can tile straight on to the new flooring (with WP first)
- less movement for floor tiles
I would like a seamless shower, so plan to drop subfloor to accommodate the tile over shower tray. Issue is that standard shower tray is 25mm deep, flooring is only 19mm, so dropping the floor flush with top of joists* will not be enough for tray to be flush with flooring.
So options are:
- Notch out top of joists 6mm
- Add layer of 6mm cement sheet to flooring to raise floor??
Pretty sure option one is not in code - especially given joist height is only 90mm (min joist spec), although keen to hear any workarounds.
* Regarding the joists, currently under both the shower and bath wastes which are at opposite ends of room the joist has been cut at some point for the plumbing, so there is actually no joist under current shower tray, just some unsupported floor boards??:shock:
The joist that is there spans 2 bearers so I assume works due to overhang? It is obviously not under any walls, just the floor
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Under shower
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Under bath
So regardless of what decision is on shower tray, Should I add a new joist alongside cut one?