When going over underfloor heating, the substrate onto which the microcement is laid needs to be dry. The moisture content in the floor should be no more than 4-5%.
Ideally, the underfloor heating should have been operational for at least 2 weeks AFTER the full cure of the substrate below.
The underfloor heating should be switched off and allowed to cool down prior to application of the microcement otherwise it will dry too quickly.
The microcement can then be applied as per the application instructions. Once it is finished the sealer can then be applied after 24-48 hours.
You can turn on the heating again 7-days after microcement application.
Both the microcement and sealer will take about 30 days to reach full strength so we recommend the floor is treated with care for the first month.
A visual with a flooring cross-section indicating the subfloor or underlayment layer, the possible cork/insulating layer, the electric underfloor heating elements, the self leveling cement or thinset layer, and then the microcement layer & sealer would be helpful. — Thanks!