how long before tiling over new 75mm screed

[Post and beam]

Walkable after 48 hours but very slow to be regarded as fully 'set' .  So when is it ok to tile the kitchen floor over my 75mm wet screed which is due next thursday.

[Nickfromwales]

15 minutes ago, Post and beam said:

Walkable after 48 hours but very slow to be regarded as fully 'set' .  So when is it ok to tile the kitchen floor over my 75mm wet screed which is due next thursday.

Wet what please? Exact type (cementitious or gypsum or dry S&C) plz?

[nod]

Presuming sand and cement screed 

It’s normally a mill per day 

 

[Post and beam]

32 minutes ago, Nickfromwales said:

Wet what please? Exact type (cementitious or gypsum or dry S&C) plz?

Cement i believe, apologies

[Post and beam]

The fully 'gone off' time is quite a long time due to it being greater than 40mm. So i suppose my question really is, can it be tiled before this?

[JohnMo]

37 minutes ago, nod said:

normally a mill per day 

75 days is a long time.

 

That's why I did my 100mm before the walls. Plenty of time to dry. But still had too much moisture to put wooden floor down without epoxy membrane.

[saveasteading]

6 hours ago, Post and beam said:

75mm wet screed which is due next thursday.

The omly way to be sure is by testing the moisture level. It varies dramatically acc to product, water content temperature and humidity.

 

If the location is dry and warm then it is much faster than 1mm/day. Especially for a dry mix or any without excess water (most then goes into the chemical structure)

[nod]

I’ve seen plenty of tiled floors lifted due to being tile to early The moisture has to go somewhere 

If you get the screed down  as soon as watertight It’s unlikely to be an issue Testing for moisture isn’t that accurate 

Or use liquid screed and tile within days 

[Post and beam]

32 minutes ago, nod said:

Or use liquid screed and tile within days 

75mm wet cement screed in our case. 

[Redoctober]

When we had ours put down, the UFH guy suggested a way of seeing whether or not the moisture had gone. He said tape down a large square bit of plastic sheeting to see if any "mositure" apperared on the bottom of it overnight. 

 

He also recommended using a particular progrmme on the UFH system which ran the heating for a period of time - warming the slab up nice and slowly - reaching a peak of around 40C - before coming back down.  

[saveasteading]

1 hour ago, Post and beam said:

75mm wet cement screed in our case. 

No problem. If doing it yourself then bear in mind the issue of not adding water to the design mix:   as well as extra drying time it will crack more.

If using a builder they like to add water for their own ease.

If getting it delivered, the driver insists on a signature for extra water (because they know the problems arising) . Tell him he is not to add water.

If mixing on site, be strict on the mix recipe.

 

you should put polyethene or hessian over it after a few hours, when safe to do so without marking. That keeps it damp and it will be the stronger for it, barely crack visibly, and,  counterintuitively  dry more quickly after the covering is off.

 

The screed will then hydrate, taking most water into the chemistry and it will dry in 2 weeks or so IF you keep the rain off it. Don't be tempted to heat it.

 

Tell us how it goes please?

 

My experience is mostly with concrete floors of 150mm, or more,  desperately needing them dry enough for covering.   1 day per mm = 5 months .

Suffice to say it never took more than 2. BUT we followed all the above rules about water and curing.

[saveasteading]

4 minutes ago, Redoctober said:

to see if any "moisture" appeared on the bottom of it overnight. 

That's a good way of delaying the job or passing reposnsibility,  if you want to. I think that is extreme.  On the other hand, if that works you know it's very ok.

[Redoctober]

48 minutes ago, saveasteading said:

That's a good way of delaying the job or passing reposnsibility,  if you want to. I think that is extreme.  On the other hand, if that works you know it's very ok.

 

I don't think there was any meaning in his suggestion, other than simply trying to offer me a way, that would re-assure me that the mositure in the slab had been dealt with. I did employ this method and it seemed to provide me with that re-assurance I needed prior to tiling etc. 👍

[nod]

I laid ours myself 

200m2 

I was nowhere near ready for tiling after 75 days 

 

Back in the day I would lay a screed in the morning and in the afternoon 

Of course Things have moved on since then 😂😂😂

[saveasteading]

1 hour ago, nod said:

lay a screed in the morning and in the afternoon 

You haven't finished the sentence....in the afternoon you went and did what?

[Nickfromwales]

5 hours ago, saveasteading said:

You haven't finished the sentence....in the afternoon you went and did what?

Went to get his hair done and a manicure! 💅 obvs. 🙄