Fast drying screed

[hendriQ]

I'm confused by the general rule that is oft quoted here that screed dries at 1 day per 1mm, so a 50mm thick screed would take 50 days, and after that one counts 2mm per day, so a 70mm thick screed would take 90 days.

That is a very long time. If that's the case, what is the downside of using something like this: https://ardex.co.uk/product/ardex-a-29/ which appears to dry much much faster? 

[nod]

4 minutes ago, hendriQ said:

I'm confused by the general rule that is oft quoted here that screed dries at 1 day per 1mm, so a 50mm thick screed would take 50 days, and after that one counts 2mm per day, so a 70mm thick screed would take 90 days.

That is a very long time. If that's the case, what is the downside of using something like this: https://ardex.co.uk/product/ardex-a-29/ which appears to dry much much faster? 

That’s sand and cement screed 

normally 75 mil =75 days 

Flow screed drys much quicker and can be tiled after a week

[jayc89]

We used Longfloor IntegraCure (http://www.longfloor.co.uk/wp-content/uploads/2020/04/LONGFLOOR_INTEGRACURE_Brochure_A4_8pgs_LowRes-1.pdf) which was ready to accept tiles once the UFH had been commissioned and cooled again.

[hendriQ]

1 hour ago, hendriQ said:

I'm confused by the general rule that is oft quoted here that screed dries at 1 day per 1mm, so a 50mm thick screed would take 50 days, and after that one counts 2mm per day, so a 70mm thick screed would take 90 days.

That is a very long time. If that's the case, what is the downside of using something like this: https://ardex.co.uk/product/ardex-a-29/ which appears to dry much much faster? 

Thanks @nod But is there any disadvantage to the quick drying one? If not, why doesn't everybody use them?

I'm planning on using this externally, as a sub-base for a micro-cement topping. At the moment we have an external cement slab that was poured several months ago on top of hard-core. The plan is to put a DPC membrane on top of the slab, then pour a 100mm of screed on top of that and then the microcement topping. But I don't know which screed to choose. The quick drying stuff just seems to good to be true. 

[nod]

It’s simply cost 

Flow screed comes in about a third more expensive 

Most here don’t have an issue with drying times 

I laid ours at the beginning of summer and it was 6 months before I needed to put floor coverings down 

As tiling contractor I’ve found flow screed pretty bombproof 

[hendriQ]

2 hours ago, nod said:

It’s simply cost 

Flow screed comes in about a third more expensive 

Most here don’t have an issue with drying times 

I laid ours at the beginning of summer and it was 6 months before I needed to put floor coverings down 

As tiling contractor I’ve found flow screed pretty bombproof 

That's very helpful. Thanks. We have to keep the external screed dry until the microcement topping is applied, so a fast drying flow screed is going to help, as otherwise we will need to have a tent up in the garden for 5 months!

[nod]

1 hour ago, hendriQ said:

That's very helpful. Thanks. We have to keep the external screed dry until the microcement topping is applied, so a fast drying flow screed is going to help, as otherwise we will need to have a tent up in the garden for 5 months!

Ideal for what you need 

[hendriQ]

@nod thanks for your help. Do you think it matters if we exceed the recommended maximum depth of that Ardex screed I linked to by 20% of so? Maximum depth is 75mm and we need to lay it to 90mm or even a few mm more than that.

[Nickfromwales]

1 hour ago, hendriQ said:

@nod thanks for your help. Do you think it matters if we exceed the recommended maximum depth of that Ardex screed I linked to by 20% of so? Maximum depth is 75mm and we need to lay it to 90mm or even a few mm more than that.

You can check with their tech dept and see if they’ll allow you to introduce a 6mm aggregate to the mix. 
With A38 you can, and it’s mixed on site with a paddle mixer so you just add as you go.

I can ask my screed guy for you if you like? I mentioned using A38 on a previous project ( walk on in 45 mins, and lay ceramic tiles in 4 hours !!! ) and he mentioned another product which he said was better again. Can’t remember the name of it for the life of me, sorry. 

[nod]

6 hours ago, hendriQ said:

@nod thanks for your help. Do you think it matters if we exceed the recommended maximum depth of that Ardex screed I linked to by 20% of so? Maximum depth is 75mm and we need to lay it to 90mm or even a few mm more than that.

No