Joisties Underfloor Insulation for Floors with Steel Joisties 

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Joisties: Innovative Underfloor Insulation for Steel Joists Explained

steel joisties insulation and installation

Why Have Steel Joists?

Floors with steel joists are a modern construction choice, favoured for their strength, durability, and resistance to pests and rot, making them particularly suitable for buildings in termite-prone areas or those requiring long spans without support columns. However, steel joists present a significant challenge known as thermal bridging, where the high thermal conductivity of steel allows heat to transfer rapidly through the joists. This can lead to substantial heat loss in the winter and heat gain in the summer, undermining the overall energy efficiency of the home. 

Underfloor Insulation for Steel Joists?

To effectively mitigate the issue of thermal bridging in steel-joisted floors, innovative insulation solutions are necessary to enhance energy efficiency and maintain indoor comfort. This is where Joisties come into play. Joisties are specifically designed to address the unique challenges posed by steel joists. By providing a thermal break and holding insulation firmly in place, Joisties significantly reduce heat transfer through the steel, ensuring a more energy-efficient and comfortable home.  Joisties can be seamlessly integrated into your underfloor insulation strategy to tackle thermal bridging and improve your home’s overall thermal performance.

What Are Joisties?

Joisties are specially engineered insulation components tailored for steel joists, providing both structural support for additional insulation and direct insulation to the joists themselves. Recognizing the need for a solution that addresses both the insulation of the joists (to provide a thermal break) and the space between each joist, ecoMaster has developed Joisties to fill this niche effectively.

This innovative system secures your underfloor insulation in place while minimizing thermal transfer through the steel. Equipped with purpose-designed fitting tools and a reliable, one-application adhesive, installing Joisties to the underside of any steel joists, whether “C” sections or box sections, is remarkably easy. Think of Joisties as cosy socks for your steel joists, keeping the cold at bay and your home comfortably warm. By providing a thermal break and holding insulation firmly in place, Joisties significantly reduce heat transfer through the steel, ensuring a more energy-efficient and comfortable home.

Key Features and Benefits:

→ DIY Friendly: Joisties are designed for easy installation, making them accessible for homeowners who prefer to handle their own home upgrades.

→ Fire Compliance and Rodent Resistance: These products meet stringent fire regulations and are designed to be resistant to rodents, addressing common concerns in underfloor insulation.

→ Durability: Joisties are made from polyester fibre, which does not degrade over time due to moisture, mould, or mildew. They are non-irritant, non-toxic, and safe for home environments.

→ High Insulation Rating: Among the highest-rated underfloor insulation solutions available, they provide exceptional thermal efficiency.

→ Water Resistance:  Joisties are water-resistant, ensuring that they maintain their insulating properties and structural integrity even in damp conditions.

How to Install Joisties:

You will need: 

→ Joistiessemi-rigid boards made from heat-bonded polyester fibres.

→ Joisties Adhesive – durable, water-proof bond between steel and joisties

→ Joisties Fitting Tools, which are magnetic to easily align with steel joists

→ Standard installation tools like utility knives for any necessary sizing adjustments

→ Headlamp, eye protection and tarps as per a standard underfloor insulation 

Installation Process:

Preparation:  Overview of Joisties

Prepare the Area: Ensure the underfloor area is clean and accessible.

Layout: Using the Joisties fitting tool
Measure and plan the layout of the Joisties according to the joist configuration.

Adhesive Application:  Using the Joisties adhesive
Apply the Joisties Adhesive to fix the Joisties directly onto the steel joists. This adhesive is specially formulated for strong, lasting adhesion.

Positioning:   Fitting the Joisties

Use the magnetic Joisties Fitting Tools to accurately place the Joisties on the joists. This ensures they are perfectly aligned and secure.

Insulation Placement: Fitting the Polyester Insulation
Once the adhesive has set, typically after 24 hours, position the bulk insulation between the joists, using the Joisties as support.

Troubleshooting Common Installation Challenges:

  • Adhesive Issues: Ensure the adhesive is applied correctly and allowed to set for the recommended time. Over or under-applying can affect the stability of the Joisties. Please watch the videos carefully.


  • Cutting to Size: Use a sharp utility knife to make precise cuts on the Joisties. For adjustments around obstacles like pipes and wires, measure and cut carefully to maintain insulation integrity.


Joisties revolutionise how insulation is installed in steel-framed floors, providing an effective, easy-to-install solution that enhances the comfort and energy efficiency of your home. For more detailed installation guidance, ecoMaster provides a series of instructional videos that walk you through each step of the process.

To explore more about Joisties and view installation tutorials, visit ecoMasterStore where comprehensive resources are available to assist you in making your home the most comfortable place on earth.


People Also Ask:

What are Joisties made from?

Joisties are crafted from polyester fibres, that are compressed into a firm, durable board. This material is chosen for its excellent insulation properties, as well as its resistance to moisture, mould, mildew, and rodents. Polyester is also non-irritant, non-toxic, and safe for use in residential settings.


How do Joisties work with different types of steel joists?

Joisties are versatile and can be adapted to fit various steel joist configurations, including both “C” sections and box sections. Their design ensures they can be easily attached to the underside of the steel joists, using special adhesives and fitting tools. This adaptability makes Joisties suitable for a wide range of steel-framed floor insulation projects.