How to Install Underfloor Heating: A Step-by-Step Guide for Hydronic Systems

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Hydronic underfloor heating is one of the most efficient and comfortable ways to heat a space. When installed correctly, it delivers even heat distribution, quiet operation, and long-term reliability.

This guide walks through the key steps of installing a panel-based hydronic radiant system, with a focus on proper preparation, installation, and startup.

Before You Start: Planning Is Everything

A successful radiant system begins before any materials are installed.

Pre-Installation Checklist

  • Heat load calculation completed
  • System layout and loop design finalized
  • Manifold location determined
  • Tubing size and loop lengths defined
  • Mechanical system selected (boiler, mixing, controls)
  • Materials staged and ready on site

Proper planning ensures the system performs as intended and avoids costly adjustments later.

7-STEP INSTALLATION FLOW

1

Prepare Subfloor

Level, dry & clean

›
2

Lay Insulation

50mm rigid foam

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3

Fix Panels

Clip to insulation

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4

Run PEX Tubing

Follow loop design

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5

Pressure Test

6 bar / 30 min

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6

Pour Screed

Cure 4–6 weeks

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7

Commission

Balance & thermostat

Tools and Materials

Typical materials include:

  • Radiant panel system (such as WBI RadiantBoard, ThermalBoard, or EPS panels for slab applications)
  • PEX tubing (size per system design)
  • Manifold and connection fittings
  • Fasteners or approved adhesive (depending on installation type)
  • Basic layout, cutting, and measuring tools

Step 1: Prepare the Subfloor

The subfloor must be ready before installation begins.

  • Ensure the surface is clean, dry, and structurally sound
  • Check for flatness and correct any uneven areas
  • For concrete, verify moisture conditions
  • For wood subfloors, confirm proper fastening and integrity

A properly prepared surface ensures good panel contact and consistent system performance.

Step 2: Install the Radiant Panels

  • Lay out panels according to the system design
  • Align panels carefully to maintain proper tubing paths
  • Fasten panels using approved methods based on the substrate
  • Keep layout consistent to match the tubing plan

Taking time here makes tubing installation faster and more accurate.

Step 3: Install the PEX Tubing

  • Follow the system layout when installing tubing
  • Press tubing fully into panel grooves to ensure proper contact
  • Avoid kinks and sharp bends
  • Maintain loop lengths and spacing as specified in the design

Each loop should be installed cleanly and consistently to ensure balanced system performance.

Step 4: Connect to the Manifold

  • Connect each tubing loop to the manifold
  • Label circuits clearly for identification
  • Use proper fittings and secure all connections

Final mechanical connections should comply with local codes and may require a licensed professional.

Step 5: Pressure Test the System

Before covering the system:

  • Perform a pressure test according to PEX manufacturer guidelines and local code
  • Maintain pressure for the required duration
  • Inspect all connections for leaks

Pressure testing is critical. Fixing issues after the system is covered is much more difficult.

INSTALLATION TIMELINE

Subfloor Preparation1–2 days
Insulation & Panels1 day
PEX Tubing & Manifold1 day
Pressure TestingHalf day
Screed Pour & Cure4–6 weeks
Flooring & Commission1–2 days

Screed cure time dominates the schedule — allow 4–6 weeks minimum.

Step 6: Install Finished Flooring

Once the system passes testing:

  • Install flooring according to manufacturer guidelines
  • Confirm compatibility with radiant heat
  • Follow recommended temperature limits

Common flooring options include:

  • Tile
  • Luxury vinyl plank (LVP)
  • Engineered wood
  • Hardwood

Step 7: Commission and Balance the System

After installation is complete:

  • Fill and purge air from the system
  • Set and verify flow rates at the manifold
  • Balance all loops
  • Gradually bring the system up to temperature

Important: Increase temperature slowly to protect flooring materials and ensure system stability.

PRE-HANDOVER COMMISSIONING CHECKLIST

✓Pressure held at 6 bar for 30+ min
✓All joints visually inspected
✓System flushed and refilled clean
✓Manifold valves balanced per zone
✓Thermostat and floor sensor wired
✓Anti-scald limit set at 45°C or below
✓System running at design temperature
✓Floor surface temp verified ≤ 27°C
✓Three-point floor temp measurement done
✓Handover documentation signed off

Frequently Asked Questions

How long does installation take?+
Timing depends on the size and complexity of the project, but panel systems typically install faster than poured systems.
Can radiant heat be installed over concrete?+
Yes. Insulated panel systems are commonly used over existing slabs in retrofit applications.
Is hydronic radiant heating efficient?+
When properly designed and installed, hydronic systems can operate efficiently at lower water temperatures compared to traditional heating methods.

Key Takeaways

  • Proper design and planning are essential for performance
  • Subfloor preparation directly impacts results
  • Panel systems simplify installation and improve consistency
  • Tubing must be installed carefully to avoid damage
  • Pressure testing is a required step before covering
  • System startup should be gradual and controlled

Final Thought

Installing hydronic underfloor heating is a straightforward process when approached step by step. Attention to detail during planning and installation is what determines long-term performance.

Panel-based systems, such as WBI RadiantBoard and ThermalBoard, are designed to simplify installation while improving heat transfer and overall system efficiency, making them a practical choice for both new construction and retrofit projects.