Liquid screed without concrete sub base?

[applestump]

Hi everyone. We've received a quote from a builder for replacing the kitchen floor in our terraced house. There's no concrete slab quoted for. He's quoted for the following layers:
- well consolidated hardcore and crushed stone
- 120mm insulation
- 1200 gauge DPM
- 50-75mm anydrite liquid screed

I spoke to the builder and he's said a concrete slab isn't necessary as the screed is strong enough and it's what's used everywhere now. All I can find online suggests that a concrete slab is required. Is this true, and the newer liquid screed construction methods don't require a concrete slab?

 

[crazydaze]

Aside from the slab issues, what flooring product were you planning to fit over the Anhydrite ?

 

[A Trowel]

Simply ask your “ builder “ if it meets current building regulations, when he tells you it doesn’t need to, politely decline his quote.

 

[applestump]

Aside from the slab issues, what flooring product were you planning to fit over the Anhydrite ?

Hey crazydave, we’re looking at solid oak parquet herringbone, 24mm thick

 

[crazydaze]

Make sure you get the latence ground off the anhydride a week or so after it’s installed/pumped, you then need to ensure the floor is dry to 75%RH with a hydrometer which will take a few weeks before screeding - the floor must be screened no matter how flat the builder claims the Anhydrite will be - and then installing the oak flooring. A Hydrometer should be the only way to check the Relative Humidity of Anhydrite, hand held testers, even protimeters will not be accurate.

This is essential.

Don’t trust a builders description of what is a fast drying, fast install substrate when it comes to Anhydrite.

If you are at all unsure if surface preparation, speak to the oak flooring manufacturer.