thinnest subfloor for tiles

[havabeer69]

so in a bit of a quandary as we're getting our laundry and showers re-done.


the existing floor was a screed bed, on 17mm ply on 90mm(ish) hardwood joists and bearers. the previous owners how ever laid tiles over tiles on the screed

we're wanting to get the smallest height transition between the kitchen and laundry as possible. the plumber doing the works is saying he needs a 40mm water stop angle to meet code, but might be able to get away with a 32mm which will put us back up to roughly the old floor finished height.



so unsure if I really have two options which are:
see if anything subflooring material available that's less then current 17mm ply (which is going to be removed and replaced with 19mm scyon)
or
cut/route the joists down 10 - 15mm and reinforce them by either packing underneath or using something like a 75mm PFC bolted to the side or some type of angle



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ignore the termite damage, its old and will be fixed up

[havabeer69]

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[droog]

It’s probably lost in translation somewhere but where is the 32 and 40 mm coming from?

Generally as I understand it the water stop finishes around 5 mm above tiles, most tiles here are 8-10mm depending on type and 2-3mm of adhesive so 18mm water stop height should cover it ?

The first photo ? How big is the step, from the picture it looks big like 60-70mm ??

[havabeer69]

It’s probably lost in translation somewhere but where is the 32 and 40 mm coming from?

Generally as I understand it the water stop finishes around 5 mm above tiles, most tiles here are 8-10mm depending on type and 2-3mm of adhesive so 18mm water stop height should cover it ?

The first photo ? How big is the step, from the picture it looks big like 60-70mm ??

I think its somewhere in the code and the thickness off the screed to get the fall required.

but you're correct. The first photo is to just show the ply and water proof. the step/transition i'm trying to avoid is on the far side where it goes to the floor boards

[r3nov8or]

Looks like you have good access under there (and even better when you take up the old floor), so you should be able to trim down the existing joists, and depending on their remaining depth and spans etc, if required add more joists or a bearer down the middle

[droog]

I think its somewhere in the code and the thickness off the screed to get the fall required.

but you're correct. The first photo is to just show the ply and water proof. the step/transition i'm trying to avoid is on the far side where it goes to the floor boards

No idea of the floor layout and need to check NSW regs but perhaps not using screed is an option ?

In VIC using compressed sheet and sloping it to the drain is a thing. No screed just waterproof and stick tiles down.