Liquid screed without concrete sub base?

28 Sep 2023
Reaction score
United Kingdom
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?
Sponsored Links
Aside from the slab issues, what flooring product were you planning to fit over the Anhydrite ?
Simply ask your “ builder “ if it meets current building regulations, when he tells you it doesn’t need to, politely decline his quote.
Sponsored Links
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.
Last edited:

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local