Fine-tuning floor gradient for wetroom

[andyscotland]

My garage conversion has an en-suite wet room.

 

The existing garage slab has a slight gradient throughout, which is handily in the right direction for the wetroom fall. I'd hoped that would be enough to do the trick, having read a while back that the ideal was about 1.5%. The plan was a linear drain along one wall, perpendicular to the slope.

 

However I'm now laying I lay the subfloor the gradient isn't quite even across the space. In the bathroom area it's a very gentle curve flattening towards the shower. So the uphill 1500mm averages about 1.4% but the final metre with the nominal shower is only about 0.8%.

 

My current buildup on the slab is PIR, 18mm chipboard, 15mm underfloor heating overlay boards, then tanking/tile.

 

Does anyone have any bright ideas for how to increase / even out the fall slightly? Is there such a thing as firring strips of sheet material? Some way I could (evenly) pack between the chipboard and the UFH panels?

 

I can't just level the whole thing and start again with e.g. a ready made former as the doorway is parallel to the slope and I don't have height tolerance to raise the level of the corridor adjacent due to doorway heights at the front of the building.

I would ideally not reduce the PIR, as I'm already kinda at rock bottom for UFH...

[ToughButterCup]

Andy, any chance of a diagram? 

[andyscotland]

@AnonymousBosch yes of course, sorry - should have posted one last night but I was sitting in the garage scratching my head and typing on the phone

 

Here is the plan view of the relevant section with rough annotations:

 

 

And here is a section through the current intended floor buildup on top of the slab:

 

Does that help?

 

 

[andyscotland]

Thinking about this a bit more today, I wonder if the solution is to skip the wet UFH under the bathroom and use electric tile mat instead. 

 

I could then use tile backer boards - possibly direct on the PIR? - with a pre-made tapered board in the lower half of the bathroom to increase the gradient there.

 

Would have the advantage of simplifying the wet UFH controls/plumbing while still allowing the bathroom floor to have a longer heating period to dry it after a shower, perhaps at a different temp than the primary heating for the bedroom and utility.

 

The only other thing I can think is to try and screed it but I think it'll be pretty thin and at risk of cracking...

 

[andyscotland]

Anyone any thoughts?

 

Another mad idea I've had is to make up a jig and attempt to cut / rasp / sand the last metre of the PIR into an even taper following the steeper gradient in the uphill section.

 

It'll be a messy job, but I reckon I can probably do it fairly accurately and it's only 1m²  and probably at most 10mm to come off at the downhill end. If I can get the PIR to follow the same gradient all the way down then the chipboard can follow that and the buildup above can be as planned. Might that work?

[Temp]

I'd fit a large tray (1200/1000 x 800/900) and screen instead of a wet room because I hate going in later and getting wet socks.

 

Perhaps something like this (but I've no experience of this make/supplier).

https://www.ebay.co.uk/itm/Walk-In-Shower-Enclosure-Cubicle-1200x800mm-Stone-Tray-Free-Waste/192154199587?hash=item2cbd486623:g:FfkAAOSwc49Y6H3D

 

They are typically supported on a timber frame (2x4), 18mm WBP then mortar. Trays have fall built in so are set level by adjusting the timber frame.  You can get trays that are as shallow as 25mm (overall height) and due to the fall and thickness there is only a very slight difference in height where you go in. Perhaps as little as 5mm.    

 

 

 

Edited February 20, 2020 by Temp

[Temp]

Actually the shower area for that one is only about 600x800 so I'd fit a wider screen and reduce door width a bit.

[andyscotland]

@Temp thanks. I'll give it some thought, but I'm really quite keen to go for level access wet floor if possible - we want the space to be as wheelchair-friendly as we can get it within the space constraints.