ᐅ Screed with or without unused dimpled membrane?

Hello everyone,

In the attic, we have underfloor heating in some rooms and ceiling heating in others.

Now, in the bedroom (which has ceiling heating), grooved plates intended for underfloor heating were accidentally installed. In these areas, only partial new screed should be added, but no underfloor heating.

The screed installer now says we can just leave the grooved plates in place (underneath them there are roughly 1 cm (0.4 inches) thick polystyrene insulation boards) and cover them with screed.

Of course, leaving them in place doesn’t cause any harm, but wouldn’t it still be better to remove the plates and pour the screed all the way through?

Thank you very much for your help!

Hello questioner,
What’s done is done!
Do it as suggested. The screed mortar will simply be laid over the dimpled membrane. This does not cause any disadvantages at all!
Regards, KlaRa

There is still Styrofoam insulation under the dimpled membrane. Is it a problem if the screed is poured directly onto the Styrofoam? I’m asking because the dimpled membrane is laid quite loosely.

The dimpled membrane, as you described and also installed on site, was intended to support a screed mortar. Whether it includes heating elements (as is common) or not does not change the final situation!

The screed mortar cannot lay directly on the impact sound insulation if the dimpled membrane or system panel was correctly installed. If it was (which is only hypothesized here) not installed properly, then the screed mortar, even with heating elements, would have reached the impact sound insulation.

Putting theory and assumptions aside: Have the screed poured above the system panel – and that’s that!

Best regards, KlaRa