How to Finish a Concrete Floor with Underfloor Heating Installed

✔ Step-by-Step: How to Finish a Concrete Floor with Underfloor Heating

1. 1

   Begin with a Clean, Pressurised UFH System

   Before any concrete is poured, the UFH pipes must be filled, bled, and pressurised. This keeps them rigid during pouring and ensures damage can be spotted early. Pressure testing should be completed in line with system requirements and maintained throughout the pour and finish. All manifolds and junctions should be protected and clearly marked.

2. 2

   Pour in Stages with Consistent Control

   Place concrete gradually over the prepared UFH zone, working from one side to the other. Avoid dumping large volumes directly over pipes. Use rakes or placement tools to guide the mix around the pipework without disturbing fixings. A first layer of 30 to 50 mm can be placed to encapsulate the pipes, followed by the remaining build-up to the final slab height. Keep the mix consistent and well-managed across zones.

3. 3

   Use Screed Bars or Laser Screeds to Maintain Levels

   Use fixed screed rails, pins, or a laser screed system to maintain correct slab thickness across the floor. Depth above the pipes should remain between 50 and 75 mm depending on the spec. Level the surface in multiple passes to avoid hollow spots or excess build-up over certain zones. Use a straightedge to check for dips or high points during the process and correct as needed before the surface stiffens.

4. 4

   Trowel the Surface According to the Finish Required

   Once the bleed water has evaporated and the surface begins to set, start trowelling based on the finish required. Hand-trowelling or power-floating may be used depending on the specification. For structural or screed slabs, a smooth flat finish is usually enough. For polished concrete finishes, a higher-grade finish and power-floating are essential. Avoid over-trowelling early, as this can seal in moisture or cause surface laitance.

5. 5

   Cure the Concrete Slowly and Evenly

   After finishing, the concrete must be cured gradually to prevent shrinkage and cracking. Use curing blankets, sprayed membranes, or plastic sheeting to retain moisture. Avoid direct sun or drafts that can cause rapid drying. Do not switch on the UFH system during curing. Allow a minimum of 28 days before applying finishes or switching on heating. Controlled curing ensures long-term strength and prevents thermal stress once the UFH is operational.

6. 6

   Cut Movement Joints if Required

   Depending on the slab size and reinforcement design, control joints may need to be cut into the surface. These help direct shrinkage cracks and relieve tension within the slab. Joints should be placed away from UFH pipe zones where possible and cut to the correct depth, usually one-quarter of slab thickness. Always check the heating layout before cutting to avoid pipe damage.