Efficient planning to avoid common underfloor heating mistakes

Image of underfloor heating installation

While the benefits of underfloor heating are easy to realise, installing a UFH system correctly is equally important to consider. Failing to carry out installation correctly can reduce system performance, eventually diminishing the value of the investment.

By understanding where mistakes are likely to occur, installers can develop strategies to limit the potential for error. This ensures that work is completed to the required standard first time round because as they say, prevention is better than the cure!

Common Mistakes that lead to an Ineffective Underfloor Heating System

Today we will share some common mistakes that could lead to an ineffective UFH system performance and how installers can avoid them.

Mistake one: Preparation (or lack of…)

By failing to prepare, you prepare to fail (ok, we’ll stop with the clichés now, you get the idea!) Ensuring the correct level of planning allows installers to anticipate any issues before they arise. This sounds very simple in theory but installers can sometimes fail to understand the exact project requirements at the planning stage. Some installers may fail to take the floor construction into account when quoting for a job, only to realise they have added unnecessary complications and expense.

Speedfit offers a range of fixing methods for all types of floor construction, such as screeds & suspended wooden joists to name a few. Effective communication between a project manager, architect, & installer is crucial at the planning stage to ensure the best method of installation is chosen, that would result in a cost effective & energy efficient installation.

Image of underfloor heating system

Mistake two: A major oversight

Not all builders are aware of how UFH must be installed & may incorrectly install insulation underneath the concrete slab. Installers have a duty to help builders understand the best practice for an underfloor heating installation, namely that the insulation should be installed on top of the concrete slab and UFH systems should be installed on top of the insulation.

Image of underfloor heating with overfit insulation installation

Under no circumstances should the insulation be solely situated underneath the concrete slab when Underfloor Heating is planned. If a builder has already installed insulation underneath the concrete slab, the best solution is to go for “Overfit“, fixing method. The Overfit system utilises a grooved insulation board, which accommodates the pipe, and a wooden floor or cement board can be laid on the top.

Image of different types of floor construction used in UFH

Mistake three: Accommodating different floor constructions in a UFH system

This issue is most likely to occur on refurbishment or retrofit projects. For instance, an existing room has been extended; the original area may have traditional wood flooring and floor joists, whereas the extension could have a modern screeded floor.

A traditional wooden joisted system floor should typically require Spreader Plates or an Underfit system, whereas a screeded floor would need a Staple or Cliprail system. Differing UFH systems would normally require different operating water temperatures, but due to the flexibility of the JG Underfloor Heating Controls and with the inclusion of a Floor Sensing Probe it’s possible to strike a balance between the two systems.

In such scenarios, it is best to utilise the probe as a high limit sensor, which would prevent the screeded floor surface from becoming too hot, while the air sensor within the thermostat would continue to regulate the temperature of the room.

Alternatively, you could screed between the joists or install the Overfit system over the entire floor area. Although, this means the floor level is slightly raised.


Planning is the most important stage for any underfloor heating project and this is why we advise installers to carefully select the best solution for their project.

If you need expert advice contact JG Speedfit

Eric Winter Headshot

Eric Winter

EMEA Director of Product Development [Valves]

About the author

I've had the privilege of being a part of the RWC family for an incredible 25 years.

I joined the company in a technical support role and steadily progressed to become the Technical Director. Throughout my tenure, I've spearheaded the introduction of market-leading products that have revolutionised the industry.

In addition to product innovation, I am a member of WG14 working group, as part of the TC 164 technical committee, which is responsible for revising European and British valve standards. This multifaceted experience has equipped me with a deep understanding of the industry, positioning me as a trusted expert in my field.