Drying time

[scott23]

Hi all, dose any one know how long new screed takes to dry before you can tile on it ?. iv been told 1 day per mm of screed. dose this sound about right?

[whitebeam]

That sounds right but how quick does the floor need tiling

[Stan001]

A minimum of 3 weeks is recommended, the first week you should make sure your screed does not dry out too fast in order for the screed to attain its full strength, and then the following weeks you should expose your screed to as much air as possible to allow it to dry out. You may have to let your floor dry out for longer than 3 weeks if the weather is wet. To determine a more exact drying time before tiling (in warm dry air) allow 1 day per mm thickness up to 40mm, and for screeds over 40mm you should allow 2 days per mm thickness.

[pjc]

14 days for screed and 25.4 mm or a 1" per month for concrete unless its rapid screed then its 24 hours but also it can depend on conditions but thats as a general rule

[Dave]

You can tile on it within a few days if you use a vapour equilisation membrane..

[Ajax123]

Drying time is accepted in the screeding industry is 1mm per day for the first 40mm depth and then 2mm per day for each mm over 40mm. These rates are based on 20 degrees Centigrade and 60% relative humidity. The moisture in the screed should be below 75% relative humidity at its surface in order to assure adhesion of resillient floor coverings such as ceramic tiles and vynils etc. (Carpets, other breathable coverings and uncoupling systems offer different rules). Additiionally if the screed is not placed in a drying environment how can you say 3 weeks or even 1mm per day is sufficient time to dry it. The flooring suppliers should always advocate moisture testing of some sort to determine if a screed is suitable to lay floor coveirngs. The standards covering screeds do advocate this as do the resillients. I cannot find the information about moisture testing in the Tiling standards and this worries me a bit. Most of the manufacturers I deal with say the screed must be dry to below 75% rh before coverings are applied.

I wish I could work out where the idea that 3 weeks or other even less in some cases is the recomended drying time because this information is incorrect. The rate of drying is heavily dependent. Residual moisture is the single biggest issue we see in the UK with flooring failures over screeds but it is not the moisture itself which does the damage. The moisture promotes various chemical processes such as ettringite issues, alkaline stipping of acrylics etc etc. It can also cause water marking in the tiles.

As Dave says the only really sensible fast tracking method is to use an uncoupling membrane which acts to stabilise the vapour pressure at the interface between the screeds and the tiles.

Some screeds can be force dried which can recuce drying times but the natural drying time of screeds unless polymer modified is as above.

[Stan001]

Dave, i know you are right in saying that and have seen the membrane guys 'sell' that as an advantage ref anhydrite screeds (residual moisture can be higher, insert membrane at higher content and tile earlier). But i really don't like the idea of using membranes in this way. I suppose I'm technically wrong (in fact know i am, and Ive seen all the fancy graphics that show how it works), but in a 15sq m room (which is not very large) the centre of the room is going to be a few metres away from any 'proper' breathing point. So you insert a membrane and effectively the whole floor is sweating for the cost of just waiting a few more weeks and letting it dry properly. I really don't like the idea. Even if they breath in 2 dimensions i recon they hold moisture for ages. Mr boring traditionalist me i know. (i like my plastic etc to be at the DPM levels, not 'in' the house)

[Dave]

Modern times stan..modern times.....using a membrane can move a job on and win you the job over a fixer who will not use them and insist on a long waiting time..

Moving with the times i call it and they work just fine...been using them quite along time now..

[Stan001]

Ajax - i like your idea of stating a moisture level for normal screeds as they continually state with anhydrite, i wonder why they dont? Id still rather wait and let the floor dry normally than go fast track though. When i build a house its going to stay up for decades, it will have a warranty people can pull on if required thats for sure, but for the sake of waiting a few more weeks in order to tile to have a good floor that will last for decades - sorry guys - i don't get it. This is short termism thinking. Lots of good old traditional houses out there without layers of breathing plastic in the floors. ... i am an old f**t arnt i!

[Stan001]

Dave - you could be right mate (you normally are) but i have a house builder and a tiler hat on i guess. ... I'm really not a techno wimp (I embrace new practices and technology) but the fix here is 'just wait a few more weeks' .... vs using a membrane? humm ... I'll take the wait.

[Ajax123]

AAAArrrrggghhhh! - just typed one of my "special" posts and the computer logged me out of the forums so I got the message saying you are not logged in and therefore don't have permission to post this.........dash, balst and bortheration.

Too late to type it all out again now so will have to cast my pearls again tomorrow......

[Stan001]

ajax - and i was waiting for your post too :-) seriously - youre the guru - put us right - note to self - must save document must save document (been there done that) ... right Im off to fix a load of trashed trav - OMG

[Colour Republic]

AAAArrrrggghhhh! - just typed one of my "special" posts and the computer logged me out of the forums so I got the message saying you are not logged in and therefore don't have permission to post this.........dash, balst and bortheration.

Too late to type it all out again now so will have to cast my pearls again tomorrow......

Right if everybody could move back, no further... further, we've got one of Ajax's sepcial posts coming, make room, make room. Look madam I really must ask you to move back or you will get crushed by this biggy...

All clear Ajax, fire away

[Colour Republic]

Aj I can't hold them back much longer!

[Ajax123]

Aj I can't hold them back much longer!

Now that's just too much pressure. I forgot what I was going to say......I know I've let you all down - when I am not so tired I will come back to it and see what I can do to redeem myself.

[Ajax123]

Aj I can't hold them back much longer!

Sorry Colour you'll have to let em back in m8....I know I let you down but I forgot what I was going to say...... ..I'll try harder to redeem myself in the future

[Colour Republic]

Right boys stepping down from DEFCON 1 to DEFCON 4

You have no idea what we have to do around in preparation to one of your special posts

Dan had arranged tempoary use of all Google servers, UK power station were bracing themselves for a massive power surge, The NHS had been handing out 'survival' packs for anybody attempting to read the post in one sitting, No. 10 had issued a warning that the UK could be plunged into even more debt due the amount of man hours losts, The cost to UK businesses had been rumoured to be around £400 million. The army were drafted in for crowd control.

Phew! That was a close call!

[Ajax123]

[pete f]

Scott use bal green screed unless youre fixing natural stone

[Stan001]

... and I've got my popcorn and paid for a seat at the front - and I'm still waiting