Solid floors are often overlooked in retrofit projects, yet they can account for significant heat loss, particularly in older or heritage buildings. Retrofitting solid floors with a breathable insulation layer not only improves thermal performance but also supports moisture regulation, ensuring the long-term health of the building.
The Diasen Diathonite Thermostep.047 system provides an ideal solution. Made from natural materials, including hydraulic lime, cork, and diatomaceous earth, this insulating screed is diffusion-open and capillary-active, allowing moisture to move safely through the structure without risk of trapping damp. This makes it particularly well suited for solid masonry buildings, where managing the moisture balance is critical. Combined with its excellent insulation value (thermal conductivity = 0.047 W/mK), fast drying time, and robust finish, the system is a practical and sustainable way to enhance comfort and energy performance.
Diathonite Thermostep.047 screed can be laid directly onto floor slabs, suspended slabs, or onto a suitable base layer such as compacted foam glass aggregate. It can be applied in areas prone to damp or minor flooding and is compatible with underfloor heating systems. Suitable for both renovation and conservation projects, the system helps to enhance thermal comfort without compromising breathability.
For junctions between walls and floors, existing concrete slabs, or areas below ground, additional moisture protection can be achieved with complementary products such as Diasen Watstop tanking system. These systems create a breathable thermally efficient floor build-up (with moisture protection where needed) that supports building fabric longevity.
About Lime and Cork Insulating Floor Screed
The Diathonite Thermostep.047 screed system delivers a robust, breathable, and thermally efficient solution for upgrading solid floors in heritage and retrofit projects. Its blend of hydraulic lime, cork, clay and diatomaceous earth creates a strong but vapour-permeable layer that improves insulation while allowing moisture to migrate safely.
The system is designed to work in harmony with solid masonry walls and traditional construction methods, helping to maintain a healthy indoor environment. It’s ideal for properties where external wall insulation isn’t viable and internal insulation must be kept to a minimum. Applied at 50mm or more, the system can significantly reduce heat loss and enhance comfort while preserving thermal mass.
Diathonite Thermostep.047 is fast drying and strong enough for a variety of floor finishes, including tiles, hardwood, and natural stone. At wall junctions that need additional moisture protection, so long as the wall is not seeping water and has a moisture content less than 4%, Diasen Watstop can be used to create a reliable barrier against rising moisture without compromising the floor’s performance.
Diathonite Thermostep.047 is a breathable floor insulation screed designed for retrofit and heritage buildings. It improves thermal performance while allowing safe moisture diffusion, reducing the risk of damp and mould. The system supports high thermal mass, offering consistent internal comfort and energy savings. Made from natural lime and cork, it dries quickly, resists compression, and is suitable for use with underfloor heating. Compatible with moisture control systems like Watstop, it’s ideal for upgrading solid floors without compromising breathability or historic character. Suitable for both retrofit and new projects, it’s a sustainable, high-performance choice for ground floor insulation.
Key Benefits
Breathable
Vapour-open floor insulation system
Thermal Performance
Improves the thermal performance without trapping moisture
Compatible
Can be used with underfloor heating systems
Fast Drying
Has high compressive strength and is fast drying
Ideal for Heritage Buildings
This system is ideal for damp-prone areas and heritage buildings
Diasen Watstsop Epoxy cement-based waterproof tanking plaster
Diathonite Thermostep.047 screed Fibre reinforced insulating lime and cork based floor screed
Compacted foam glass aggregate
A typical ground floor installation consists of the following layers:
- Floorboards, flagstones or tiles
- Diathonite Thermostep.047 (40-200mm thick)
- Geotextile breather membrane
- Compacted foam glass aggregates (100-200mm deep)
- Geotextile breather membrane
- Ground soil
The compacted foam glass aggregate is used beneath the screed to achieve better U-values and improve insulation at floor voids or structural transitions.
Apply Diasen Watstop at wall to floor junctions or below-ground walls to guard against rising damp and salt contamination before installing Thermostep.047. If any below-ground wall is seeping water or has a moisture content greater than 4%, Watstop can’t be used; contact our technical team for advice.
- Diasen Watstop Epoxy cement-based waterproof tanking plaster
- Diasen Diathonite Thermostep.047 screed Fibre reinforced insulating lime and cork based floor screed
- Compacted foam glass aggregate
