Sand & Cement wet room floor screed questions

[On one]

Hi All.
Got to admit, having to use S&C to form a wet room floor is a first for me. I Got a call out of the blue from a builder who I have never come across ,quite a few other things setting off alarm bells....... Painter already in an adjoining room,waste pipes at a jaunty angle,promises of we will do this,we will do that.......
but what is the minimum thickness of sand and cement required and how long would this take to dry? Just what to be sure of my facts when I ring him up.

 

[White Room]

What are screeding onto.....

 

[On one]

Sorry!. A concrete floor.

 

[White Room]

You can take screed down to 30mm if needed but usually 50mm on concrete base with a few fibres thrown in for good measure and a slurry with sbr onto the base will insure a good grip.

 

[On one]

I reckon,I have a maximum of 45mm at the doors but less at the drain.

 

[White Room]

I think the falls to the drain is 20mm in a linear metre if memory serves me right....

 

[On one]

Re: Sand & Cement wet room floor screed questions

I think the falls to the drain is 20mm in a linear metre if memory serves me right....

Which is not too far off being achievable. But the drying times?

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The builder reckons 2-3 days!!!! lol

 

[White Room]

Re: Sand & Cement wet room floor screed questions

Which is not too far off being achievable. But the drying times?

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The builder reckons 2-3 days!!!! lol

He can wish.....BS state about a day per 1mm or at least give it couple of weeks....or 4.

 

[The Legend; Phil Hobson RIP]

Hi All.
Got to admit, having to use S&C to form a wet room floor is a first for me. I Got a call out of the blue from a builder who I have never come across ,quite a few other things setting off alarm bells....... Painter already in an adjoining room,waste pipes at a jaunty angle,promises of we will do this,we will do that.......
but what is the minimum thickness of sand and cement required and how long would this take to dry? Just what to be sure of my facts when I ring him up.

I think min for sand and cement screed is 40mm/50mm but that could be reduced to suit falls with modern technology.

I think a tanking system before the screed might be a way to go.

I will wait for Ajax to respond, he has never let me down with his advice, so I will bow to Alan's experience.

Good luck.

 

[On one]

Re: Sand & Cement wet room floor screed questions

He can wish.....BS state about a day per 1mm or at least give it couple of weeks....or 4.

That's the formula I would use on a concrete,but wondered if S&C was different.

 

[Diamond Pool Finishers]

Why don't you use a fast -track screed then you will be able to tile on to it within hours if need be ,deffo Tanking deffo SBR/cement slurry for bonding !, i think the minimum you can screed down to with traditional screed is 25mm under BS.......

 

[The Legend; Phil Hobson RIP]

Looks like I was a bit slow with my answer, but 1:60/ 1:80 for falls imo as stated 1mm per day up to 40mm then 2 days per mm after that. It's my age, by the time I have typed, a dozen people have replied.😳

 

[On one]

I think min for sand and cement screed is 40mm/50mm but that could be reduced to suit falls with modern technology.

I think a tanking system before the screed might be a way to go.

I will wait for Ajax to respond, he has never let me down with his advice, so I will bow to Alan's experience.

Good luck.

Would tanking first before the S&C screed is laid, inhibit the drying times of the screed?

 

[The Legend; Phil Hobson RIP]

Would tanking first before the S&C screed is laid, inhibit the drying times of the screed?

Again I think Ajax is the man for this but imo the sand and cement screed will cure, residual moisture content traveling to the surface, rather than going down, I just thought a tanking membrane would be a good thing for a wet room.

I'm sure Alan will put me right.

 

[On one]

Again I think Ajax is the man for this but imo the sand and cement screed will cure, residual moisture content traveling to the surface, rather than going down, I just thought a tanking membrane would be a good thing for a wet room.

I'm sure Alan will put me right.

Hi Phil
The tanking is a given,just the positioning was in question.

 

[On one]

Is Ajax watching the England football or out making a 2nd living!

 

[Ajax123]

Re: Sand & Cement wet room floor screed questions

BS 8204 part 1 is the standard that covers sand cement screeds. The situation you are talking about would be an unbonded screed (I.e. on a polythene membrane or in direct contact with an unprepared concrete slab)

The minimum depth at any point in domestic situations is 50mm and it MUST be reinforced with either d49 steel mesh or polypropylene fibres.

If it is on insulation I.e. Floating then it would be minimum 65mm and if bonded you can go to 25mm but the base must be prepared by shot blasting or grinding to remove the Laitance to expose the coarse aggregate in the screed.

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Is Ajax watching the England football or out making a 2nd living!

Cant stand footy so been out ... Sadly it was a non paying event.... 🙂

 

[Ajax123]

Would tanking first before the S&C screed is laid, inhibit the drying times of the screed?

You would be better priming the concrete underneath with an acrylic primer or SBR to limit the level of moisture into the concrete. You should technically cure the screed for seven days under polythene but if you lay it and cover it for a couple of days you would be able to use a liquid DPM on it. This will "trap" the residual moisture ( it will dry eventually) but under the DPM it will do no harm. Just make sure you put a suitable perimeter edge round it to prevent moisture migrating into the surrounding materials (walls, other screed etc) the DPM should be laid and dry sand broadcast into it before it dries. When dry vac up any remaining sand tank the walls as normal and then tile using your usual flexi adhesive. Sounds like a lot of work but it's only a small area so will not take long or present much effort IMO .

 

[Ajax123]

Oh and use a plasticiser in your screed to aid compaction and make sure it is not too dry.... So many screeners use sand cement screeds that are too dry... Causes real issues with compaction.

 

[Mr Tiler]

Wow what a lot to take in ajax... About the perimetre to prevent the screeds moisture spreadin tho. Whats ideal to use in your opinion? And once that void hasbeen created and the perimetre removed... What do you fill that void with? And is there an expansion joint needed in this situation if so what is it? Very informative thanks mate

 

[Tilegods]

You can take screed down to 30mm if needed but usually 50mm on concrete base with a few fibres thrown in for good measure and a slurry with sbr onto the base will insure a good grip.

You can take sand and cement down to 0mm . Use a 4mm notch trowel and spread tile adhesive when going 10 amd under

 

[Kevbos]

Hi All.
Got to admit, having to use S&C to form a wet room floor is a first for me. I Got a call out of the blue from a builder who I have never come across ,quite a few other things setting off alarm bells....... Painter already in an adjoining room,waste pipes at a jaunty angle,promises of we will do this,we will do that.......
but what is the minimum thickness of sand and cement required and how long would this take to dry? Just what to be sure of my facts when I ring him up.

Sand and cement tiling requires you being able to screed firstly !! And then being able to fix your tiles onto the wet screed , with what they used to do a neat cement fine slurry , it's the same as waterproof rendering , the scratch coat has to be finish coated whilst still wet , other wise the drying scratch coat becomes waterproof and finish coat does not bond !! Just a 4 part sand to 1 part cement should create a waterproof mix , but you must seal or moisten area prior to screening or rendering !! But that's old school tiling , anyone that has tried to take this tiling off floors or walls will know how good it is , but it is slow and not many can do it anymore !! It's not easy to do properly

 

[Kevbos]

Hi All.
Got to admit, having to use S&C to form a wet room floor is a first for me. I Got a call out of the blue from a builder who I have never come across ,quite a few other things setting off alarm bells....... Painter already in an adjoining room,waste pipes at a jaunty angle,promises of we will do this,we will do that.......
but what is the minimum thickness of sand and cement required and how long would this take to dry? Just what to be sure of my facts when I ring him up.

Sorry forgot to mention !!! The only reason noone does the best way of tiling anymore is because of time aspects and the changes in building methods , there is I doubt not even 1 major house builder that has used sand and cement tiling in there projects for 25 years , because of drying times , and the need for the use of solid walls or floors in the houses they build , to accommodate sand and cement tiling !! I am a victorian tiler , and I see tiling over 100 years old because of this method daily , and yet it not used nowadays !!