Retrofit Underfloor Heating Systems

Adding underfloor heating to an existing property no longer requires digging up concrete floors or significantly raising door heights. ITHERME Retrofit Systems are ultra-low profile “overlay” solutions designed to sit directly on top of your existing structural floor. With systems starting from as low as 13mm–20mm in thickness, you can enjoy the comfort of hydronic heating with minimal disruption to your home’s architecture.

These systems are lightweight, fast-acting, and can be installed over existing screed, tiles, or timber subfloors, making them the ideal choice for kitchen renovations, basement conversions, and whole-house refurbishments.

Get a Retrofit System Quote & Design

Choosing Your Retrofit Solution

Because every renovation project has different height restrictions and floor finish requirements, we offer three distinct professional overlay systems:

GYPSUMDEK 18: Our premium high-output system. Made from high-density gypsum fibreboard, it offers incredible thermal conductivity and a rock-solid feel underfoot. At only 18mm thick, you can tile directly onto it, saving time and cost on extra plywood or cement board overlays.

ALUFOIL 20: An insulated overlay system featuring high-density EPS insulation bonded with a thick aluminum foil layer. It is ultra-lightweight and provides excellent lateral heat distribution, perfect for laminate and engineered wood finishes.

CASTELLATED 16: An ultra-thin “egg-crate” style tray that is bonded to the floor and filled with a specialist levelling compound. This creates the thinnest possible build-up (from 15mm) while providing a flat, level surface for any floor covering.

Frequently Asked Questions

Do I need to trim my doors?
With a total build-up as low as 15mm–20mm plus your floor finish, door trimming is often minimal or not required at all. We recommend checking your threshold heights before choosing a system.

Can I install this over existing tiles?
Yes, provided the existing tiles are sound and well-bonded. We recommend using a high-quality primer before laying your chosen ITHERME panels to ensure a permanent bond.

Which system is best for Heat Pumps?
All of our retrofit systems are designed to work perfectly with heat pumps and ITHERME offer a complete range for all floor finishes.