What Happens When Underfloor Heating Isn't Commissioned Properly
Skipping proper screed commissioning is a gamble with the kind of damage you don’t see until it’s already done. The problem doesn’t show up on day one it shows up weeks or months later, once the floor is down and the client has moved in. By then, there’s no quick fix.
This is what that failure actually looks like.
A Familiar Story
Picture a fairly typical scenario: a residential or light commercial build, underfloor heating installed, screed laid and left to dry for a few weeks. The programme is tight, so once the screed feels firm underfoot, the heating gets switched on at a normal operating temperature and the floor layer is booked in.
Three weeks after the client moves in, hairline cracks start appearing across several rooms. In one bathroom, the tiles have started to lift at the edges. The flooring contractor says it’s not their workmanship. The screed layer says the screed was within spec when it was laid. The underfloor heating installer says the system is working exactly as designed.
Nobody on site did anything wrong in isolation. They’re all describing their part of the job correctly. The missing piece is the part nobody owned: commissioning and conditioning the screed before it was ever switched on properly and that gap is exactly what causes failures like this.
What Actually Went Wrong
When underfloor heating is brought up to temperature too quickly, the screed doesn’t get the chance to expand evenly. This is thermal shock, and it produces a recognisable pattern of damage:
- Hairline to structural cracking across the screed, often following the heating pipe layout.
- Curling at perimeters where the screed has lifted slightly away from the substrate or insulation.
- De-bonding of tiles, LVT or engineered wood, sometimes appearing weeks after the floor was laid, as residual moisture finally finds a way out.
- Uneven heat output from the underfloor heating system itself, as cracks and voids disrupt the screed’s thermal mass.
Who Actually Pays For It
This is the part that makes uncommissioned screed such a costly gamble. By the time the problem shows up, the floor finish is down, the client has moved in, and several trades have left site. Remedial work usually means:
- Lifting and replacing the floor finish.
- Investigating the extent of the screed damage, which may mean opening up multiple areas.
- Re-laying flooring once the screed issue is resolved.
- Lost time, lost goodwill, and in many cases, a flooring warranty that’s no longer valid because there’s no evidence the screed was conditioned to BS8204-7.
What would have been a planned, predictable process before flooring went down becomes an unplanned, disruptive one after the client has already taken possession.
Why It's So Hard to Catch in Advance
Conditioning failures don’t usually appear immediately. The screed can look, feel, and test fine at handover. The damage often only becomes visible once the heating has run through a full cycle, or once seasonal temperature changes start putting the floor under stress in the other direction. By then, the build team has moved on to the next project.
The Fix Is Straightforward, If Someone Owns It
This isn’t a hard problem to solve. It just needs to be planned for and assigned to someone who specialises in it. A controlled commissioning programme gradually raising screed temperature, holding it, then gradually cooling it, alongside proper dehumidification gives the screed the introduction to heat it needs to perform the way it was designed to.
ForceDry built our service around exactly this gap. We’re one of the few specialists in the UK who handle commissioning and conditioning as a dedicated process, calculated against your specific screed and depth, and documented so you have evidence it was done correctly.
Don't Wait for the One Time It Goes Wrong
If underfloor heating is part of your current or upcoming project, get conditioning and commissioning into the programme now, not after a problem appears.
Get in touch with ForceDry to find out how a properly conditioned screed protects your programme, your warranty and your reputation. Or read more about our Commissioning & Conditioning service here.
Contact the team today;
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