Castellated 16 Concrete Sub Floor Heating System

System Overview

The ITHERME CASTELLATED 16 system is an ultra-low profile “renovation” solution designed for projects where floor height is critical. Unlike standard screed systems, this product utilises a slimmer 16mm castellated panel designed to house the narrower ITHERME VE-FLEX 12mm pipe installed in a spiral pattern design.

The panel features a self-adhesive backing, allowing it to be stuck directly onto a primed subfloor or rigid insulation without the need for separate clips or rails. Once the pipe is clicked into the grid, the system is typically covered with a thin self-levelling compound (minimum 20-22mm total depth), making it perfect for retrofits where a traditional 65mm screed is not feasible.

Key Features & Benefits

• Ultra-Low Profile: With a panel height of just 16mm, the system can be installed with a total floor build-up of as little as 22mm (depending on screed type).
• Self-Adhesive Backing: The panels peel and stick to the subfloor, ensuring they stay flat and secure during the pouring of the levelling compound.
• Fast-Track Installation: The “castle” grid allows for rapid pipe installation by a single person, with no specialist tools required.
• 12mm Pipe Compatibility: Uses the flexible ITHERME VE-FLEX 12mm pipe, which allows for thinner installation heights and design flexibility installed in a spiral pattern.
• High Response Time: Being encased in a thin layer of screed/compound means rapid heat-up times.

Technical Specifications

Heat Output Performance

Performance data based on 100mm pipe centres in a 22mm self-levelling compound.

Performance Overview

Due to the thin nature of the screed (usually just covering the castellations by 5-10mm), the ITHERME CASTELLATED 16 system offers exceptional thermal conductivity. The pipe is very close to the floor surface, resulting in rapid warm-up times.

Installation Build-Up

Floor Construction Hierarchy (Bottom to Top):

1. Subfloor: Existing concrete or stable timber floor (primed) or rigid insulation panel.
2. Panel: ITHERME CASTELLATED 16 self-adhesive tray.
3. Pipework: ITHERME VE-FLEX 12mm pipe clipped into castellations.
4. Screed: Self-levelling compound (poured to cover castellations + approx 5-10mm).
5. Final Finish: Tiles, engineered wood, LVT, etc.

Installation Tips & Best Practices

• Prime the Subfloor: Because the panels rely on self-adhesive backing, the subfloor must be dust-free and primed with a suitable acrylic primer to ensure a strong bond.
• Overlap the Panels: The panels are designed to overlap. Ensure the castellations nest into each other at the edges to create a continuousgrid for the liquid screed.
• Perimeter Strip: Always install the ITHERME edge expansion strip around the perimeter of the room. This allows the screed to expand/contract and prevents thermal bridging to the walls.
• Pressure Testing: Ensure you pressure test the system fully before and during the pouring of the levelling compound to detect any potential damage immediately.
• Screed Selection:  Use a “renovation screed” or flexible self-levelling compound designed for underfloor heating and thin applications.

Frequently Asked Questions

Why use 12mm pipe instead of 16mm?

The ITHERME CASTELLATED 16 system is a “Low Profile” solution. A standard 16mm pipe would require a deeper panel and a thicker screed (raising the floor height). By using 12mm pipe, we can keep the panel height to just 16mm, making it possible to install underfloor heating in rooms where you only have ~20-25mm of height to spare.

Do I need insulation under this panel?

The CASTELLATED 16 panel itself acts as a pipe carrier, not an insulator. If you are installing over an uninsulated ground floor, you will lose heat downwards. However, for intermediate floors or renovations where height is the priority, this is the trade-off. Some installers lay thin 6mm or 10mm insulation boards underneath if height permits.

Can I install this over a timber floor?

Yes, provided the timber floor is stable (no loose boards) and sealed. You should prime the timber and ensure there are no gaps where the liquid compound could leak through. The self-adhesive backing helps seal the panel to the timber.

What happens if the screed cracks?

Using the correct flexible levelling compound is vital. These modern compounds are fibre-reinforced to resist cracking even at thin depths. Always follow the screed manufacturer’s guidelines regarding minimum depths over the “castle” (usually 5mm-10mm coverage).