# Forum Home Renovation Tiling  Slab set down and screed thickness

## Micky013

Hi, 
Nearing the event of pouring the slab for my extension which incorporates bathroom and laundry. The engineer has specified nominal set downs of 30mm for bathroom and laundry. As the slab for the main living area is going to be set down 51mm to accommodate battens and floor boards, does it sound reasonable to set down the entire slab 51mm (inc. bathroom and laundry) then screed up 40mm or so to meet finished floor level? the engineer hasnt included the set down for FFL - he has only indicated that the architect needs to be consulted for that set down - I am the architect  :Biggrin:   
Ill be doing the tiling and the floor boards so would be nice to know if im on the right track regarding the screeding. 
Cheers,
Michael

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## Oldsaltoz

If you are planning a walk in shower the shower base needs to set down 50 mm, or more if it's over a meter in any direction. The rest of the room floor only needs enough set down to provide drainage to the floor waste. 
If on the other hand you plan to have a flat slab without a shower recess/set down. The you need to install a 50 mm angle around the shower to act as water stop and keep the tile surface finish 5 mm below the top of the angle for the screen fitting. The rest of the room would then have screed added to create fall to the floor waste. 
The last alternative is a 50 mm angle in the doorway creating a step up into the bathroom, an angle around the shower and re levelling of the floor area with a screed. 
Good luck.   :Smilie:

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## Micky013

Thanks Oldsaltoz. 
Our shower has been drawn in at 1m x 1m and we'd most likely going with the first scenario you described (walk in shower). The only other alternative would be to use a ceramic/plastic shower base - which i assume needs  no set down as its "self contained" so to speak. 
Just so I've got it right - going with scenario one. If we set the entire slab with a 51mm set down (including the bathroom and laundry) from FFL then I would need to set down the shower by a further 30mm to allow for screed to set fall while still being about 50mm below the bathroom FFL. 
If you were gonna be completely precise could you, set down the main "living" area of the slab by 51mm, have the bathroom and laundry areas "set up" 20mm with the shower area set down at the same 51mm as the living area. That way you only need to screed about 30mm in laundry and bathroom (rather than 50mm) and you still have the 50mm in the shower. 
I just dont know if my first example is excessive in set down? 
Cheers
Michael

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## Oldsaltoz

> Thanks Oldsaltoz. 
> Our shower has been drawn in at 1m x 1m and we'd most likely going with the first scenario you described (walk in shower). The only other alternative would be to use a ceramic/plastic shower base - which i assume needs  no set down as its "self contained" so to speak. 
> Just so I've got it right - going with scenario one. If we set the entire slab with a 51mm set down (including the bathroom and laundry) from FFL then I would need to set down the shower by a further 30mm to allow for screed to set fall while still being about 50mm below the bathroom FFL. 
> If you were gonna be completely precise could you, set down the main "living" area of the slab by 51mm, have the bathroom and laundry areas "set up" 20mm with the shower area set down at the same 51mm as the living area. That way you only need to screed about 30mm in laundry and bathroom (rather than 50mm) and you still have the 50mm in the shower. 
> I just dont know if my first example is excessive in set down? 
> Cheers
> Michael

  Hi Michael,
In a perfect world I would set the shower base down 50 mm in the bathroom and ensuite and set the wall to floor down 30 mm, making the shower base a total of 80 mm below the rest of the slab. 
I would also set down the Laundry floor by 30 mm and make sure it had a floor waste. 
The above will ensure you have enough fall for good drainage in all areas, also note that screed will not be a reliable medium at less that 25 mm thickness, so levelling the floors would be combination of screed mic and levelling compound, personally I would do the whole area with a leveling compound because it can be just a few mm thick at the waste area. 
Note, all floor wastes will need puddle flanges installed, this is best done by your waterproofer because it then comes with a warranty not to leak. 
Good luck.   :Smilie:

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## Micky013

Awesome - sounds good. 
Thanks for your help! 
Michael

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