Isolmant UnderSpecial Classic

Isolmant UnderSpecial Classic

Isolmant UnderSpecial Classic

Isolmant UnderSpecial Classic

High performance resilient layer made of polyethyle ne Isolmant Special joined on the lowerside to FIBTEC XF3 (special second generation needle-worked fibre produced according to specifications designed). It provides excellent impact sound and airborne insulation for horizontal partitions. 


10 mm and 15 mm thicknesses available.



IIsolmant UnderSpecial Classic is specific for floating screeds as provided by UNI 11516:2013 standards with any type of slab.


Specific for horizontal structures with finishing screed at least 5 cm thick.



Immagine 1


• Excellent acoustic impact sound and airborne insulation.

• Suitable for use in both renovation and new construction.

• Low thermal conductivity.

• Inalterable over time.

• Unlimited durability.

• Contact with water does not compromise performance or characteristics.

• Resistant to mould or insects.

• Easy to lay products.

• Product with overlaps.

• Easy to trim: can be easily cut with a utility knife or box cutter.

Isolmant GreenPlanet

  • Volatile Organic Compounds free (VOC A+) | (Eurofins Indoor Air Comfort GOLD Certification).

  • Eco-friendly and recyclable.

  • Recycled contenent certified by ICMQ (report no. P492)

  • Manufactured with low environmental impact.

  • Contributes to achieving credits for the environmental certification of a building according to the LEED or BREEAM protocols.

  • This product can be disposed of according to EWC n. 170604.

  • Complies with the requirements defined by the Italian CAM Edilizia for acoustic and thermal insulation materials regarding the request for high acoustic insulation performance, the percentage of recycled material and the absence of hazardous substances.

UnderSpecial becomes Gold

Indoor Air Confort Gold®

UnderSpecial earns l'Indoor Air Confort Gold® di Eurofins


The Eurofins Indoor Air Comfort certification represents the best guarantee at European level regarding the fulfillment of the low VOC emission requirements required by the market.

The standard level "Indoor Air Comfort" shows the compliance of the emissions of the product with the criteria of all legal specifications issued by the authorities of the European Union and its member states.


The higher level "Indoor Air Comfort Gold" ensures further compliance of product emissions with the criteria of many of the voluntary specifications issued by the most relevant eco-labels, with the specifications in the EU and with the requirements for sustainable building certifications (LEED, BREEAM , etc.).


Indoor Air Comfort certified products demonstrate the lowest emissions in the category and are considered the best products to ensure indoor air quality.

Indoor Air Confort Gold®

Item Specifications

Resilient layer made of physically reticulated expanded closed-cell polyethylene, joined on the lower side with a special needle-worked second generation fibre that is conceived to enhance the acoustic performance (Isolmant UnderSpecial Classic type). 10 or 15 mm nominal thickness. Dynamic stiffness s't = 8 MN/m3, s' = 20 MN/m3 for the 10 mm version (certtified values) and s't = 7 MN/m3, s'= 13 MN/m3 for the 15 mm version. Impact sound insulation .Lw = 36 dB and 38 dB for versions 10 or 15 mm respectively. VOC A+ (certified parameter), Indoor Air Confort GOLD (certified parameter). Recycled content certified by ICMQ. To be positioned with the screen printed fabric facing upwards. This product comes with adhesive to seal the overlapping fabric.

Item Specifications Copy item specification

Info & curiosity

slide 1
Particularly suitable for laying under the finishing screed of the flooring (double-layer solution), it requires the creation of a finishing screed with a minimum thickness of 4.5 cm (for UnderSpecial 8 mm) or at least 7 cm (for UnderSpecial 13 mm).
slide 2
One of the historical products of Isolmant's under-screed range, in 2017 on the occasion of the 20 years of presence on the building market, the celebratory version "Isolmant UnderSpecial 20 Anniversary" was created, which lasted a few months and immediately became iconic.
slide 3
Isolmant UnderSpecial, the first coupled product of the Isolmant range, made the history of under-screed acoustic insulation, ending up in the homes of many Italians. But that's not all: it is one of the Isolmant products with the largest foreign market.

Installation information

1/2 - Installation of Isolmant UnderSpecial

Before installing the underlay, a levelling screed must be laid using suitable materials and recipes to ensure adequate mechanical support and a plain and uneven surface.


Then the sheets of Isolmant Underspecial can be laid, which must be carefully joined using the special overlapping fabric and sealed with Isolmant Nastro Telato or Isolmant Fascia Nastro. It is also necessary to be careful to start flush with the wall with the polyethylene, avoiding leaving strips of fibre only visible near the walls: the fibre, in fact, absorbs the cement and stiffens, generating a dangerous and continuous acoustic bridge. It is therefore necessary to trim only the fibre flush with the wall in order to guarantee the presence of both layers of product over the entire surface of the floor.

1/2 - Installation of Isolmant UnderSpecial
Product with overlaps for easy installation.

2/2 - Installation of Fascia Perimetrale:

To avoid acoustic bridges, the use of Isolmant Fascia Perimetrale is recommended, to be laid along the entire perimeter of the room without interruption. The height of Isolmant Fascia Perimetrale must be chosen by the designer/ contractor, taking into account the actual height at each site, in order to guarantee that the band is about 2/3 cm higher than the flooring level.


This excess must be trimmed after laying the floor. The continuity of the installation must also be ensured along the thresholds of entrance doors and French windows, as well as in technical niches for housing the manifolds of the heating system, pillars, pilasters, doors and other wall movements.

2/2 - Installation of Fascia Perimetrale:
The excess of the flanking strip must be trimmed only after the flooring has been laid and grouted.