What happened

An extension's wet underfloor heating system was installed on a screed laid directly over the structural slab. The insulation layer under the slab was omitted.

How it was discovered

First winter — the system ran continuously and barely warmed the room. Thermal imaging showed heat escaping below the slab.

The consequences

No remedial fix without removing the floor entirely. The homeowner increased the radiator backup. Lesson learned, comfort compromised.

What homeowners can learn

Floor build-ups are invisible after pour. Confirm the layers in writing before the concrete arrives.