Spray-applied PUR: definition and principles

What is spray-applied PUR?

Spray-applied PUR is a polyurethane foam applied in liquid form using a spray machine. Upon contact with air, the two components react, causing the foam to expand within seconds before hardening into a rigid, continuous, and seamless insulating layer.

Its unique advantage lies entirely in this application method. Insulation boards must be cut, fitted, and installed. PUR, however, conforms exactly to the shape of the substrate: it flows around pipes, fills voids, and adapts to corners and irregularities without any manual adjustment.

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Why spray application changes everything for floor insulation

A raw floor is rarely level and is almost always crossed by conduits and pipes. With boards, every obstacle requires cutting, every cut creates a joint, and every joint is a potential thermal bridge.

PUR eliminates the problem at the source: the insulating layer is monolithic. On renovation projects, where floor levels are uneven and networks are exposed, the actual performance gap compared to board-based solutions is greater than technical data sheets might suggest.

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What its performance means in practical terms

PUR is among the highest-performing insulators per centimeter of thickness, outperforming granule-based solutions EPS. For the same thermal performance, a layer of PUR is therefore thinner.

This difference becomes critical in renovations. When ceiling height is fixed, doors are already in place, and the threshold cannot be raised, every centimeter saved on insulation is a centimeter gained for the screed. This is often the deciding factor between insulating properly and giving up.

Exact conductivity values vary depending on the density and the system used: these can be found on the technical data sheet for the product being installed.

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Installation requirements

Spray application requires specialized equipment and a trained operator. It is not a DIY-friendly solution, and machine settings directly influence the resulting density.

The substrate must be dry and clean at the time of application. Depending on the uniformity of the expansion, leveling may be required before pouring the floating screed over it.

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PUR or EPS?

PUR wins on performance with reduced thickness and layer continuity. EPS remains a relevant choice for filling large gaps, correcting significant height differences, or sticking to a tight budget.

The question is not which one is better in absolute terms, but which one addresses the primary constraint of the project: height or the volume to be filled. A detailed comparison can be found in our article PUR vs EPS, and both solutions are presented on our thermal insulationpage.