Home / Underscreed / E-FC-14

Robust Detail E-FC-4 is an acoustic solution for precast plank floors. This system provides a minimum 5dB improvement the requirements of Approved Document Part E. When registered with Robust Details Ltd the requirement for on-site sound testing is removed and 3 Code for Sustainable Homes / BREEAM / Home Quality Mark credits are automatically awarded.

  • Exceeds Building Regulation requirements by minimum of 5dB.
  • No need for sound testing if registered with Robust Details Ltd.
  • Provides 3 CSH/BREEAM/HQM credits upon registration.
  • System uses Isorubber Base to reduce noise transfer, this is a tough, resilient acoustic mat that can withstand the rigours of the screeding process.
  • Purpose made Isoedge strip and Isosonic Ceiling Strip are used to eliminate flanking sound transfer.
  • No long term / short term deformation of acoustic layer.
  • Suitable for use with Under Floor Heating
Specifications Acoustic Performance:
As a Robust Detail that provides 3 Code for Sustainable Homes Credits the E-FC-14 system must always achieve individual site test values of: Airborne Sound – not less than 50db (Dntw + Ctr) Impact Sound – not greater than 57db(Lntw)

This exceeds the Building Regulation (Approved Document Part E) requirements by 5dB in both cases.

Isorubber Base
Roll Size: 6mm x 1m x 10m
Roll Weight: 37Kg (14 Rolls per pallet)
Density: 635Kg/m3

Isoedge 6/260 Roll Size: 6mm x 260mm x 50m
Roll Weight: 5.2Kg (3 Rolls per Bag)
Density: 30Kg/m3

Isosonic Ceiling Cleats Bag Quantity: 100
Bag Weight: 2Kg

Isosonic Ceiling Strip Roll Size: 40mm x 25m
Roll Weight: 0.8Kg (10 Rolls in a Bag)
Density: 30Kg/m3

Isorubber Jointing Tape Roll Size: 50mm x 50m
Roll Weight: 0.45Kg (24 Rolls in a Box)


Isorubber Base is a 6mm thick acoustic insulation that is laid beneath the screed, separating it from the precast plank and absorbing impact sound. A durable product with a density of approximately 635Kg/m3, Isorubber Base does not suffer from any deterioration of acoustic performance during the normal lifespan of a building. This is because it undergoes virtually no short-term deformation or long term creep deformation under normal domestic loads. With a recycled content of approximately 90% waste rubber, a Global Warming Potential of Zero and an Ozone Depletion Potential of Zero Isorubber Base provides a means of using problematic waste material to the benefit of the environment.

Isoedge 6/260, a purpose made edge strip, is fitted around the perimeter of the screed to separate it from the walls and reduce flanking sound transmission. With an adhesive backing strip, die cuts and markings to aid installation Isoedge 6/260 has been designed to eliminate installation errors at what is generally regarded as a problem junction.

No CFCs or HCFCs are used in the manufacture of Isoedge 6/260 and it has Global Warming Potential of 3 and Ozone Depletion Potential Zero.

A metal frame utilising Isosonic Cleats or an Isosonic Ceiling system is also required to the underside of the precast plank. The type and depth of the ceiling are dependent on the precast plank thickness (please see the Robust Details handbook for further guidance on the options available).

The Isosonic Cleats provide acoustic separation to a standard MF ceiling construction. A universal fixing, they simply replace the standard soffit cleats and should be compatible with all MF ceiling constructions.

The Isosonic Ceiling treatment utilises Isosonic Hangers Type C to separate the ceiling from the precast plank. Isosonic Ceiling Strip can be used around the ceiling perimeter to help reduce flanking sound transmission.

Isorubber Jointing Tape is a cloth tape designed to adhere to the Isorubber and Isoedge range of products.

About System

The E-FC-14 system was the first under screed system to gain 3 Code for Sustainable Homes Credits status. Its consistent high performance and compatibility with all masonry flanking external wall types, including aircrete blocks (450- 800Kg/m3) make it the obvious pre-cast plank system to choose when looking for 3 Code for Sustainable Homes Credits.

The E-FC-14 system consists of 6mm Isorubber Base fitted below a minimum 65mm sand & cement screed with Isoedge 6/260 separating the screed from the wall. The structural floor must be a minimum 150mm precast plank with a minimum mass of 300Kg/m2 per unit area. This system can be used with all masonry external flanking wall constructions (450 – 800Kg/m3, 1350 – 1600Kg/m3 & 1850 – 2300Kg/m3). A metal frame ceiling supported by Isosonic Cleats with a minimum void of 150mm or an Isosonic Ceiling is also required. Both ceiling details are under drawn with a layer of gypsum based board (minimum 10Kg/m2) and have a minimum of 50mm mineral wool in the ceiling void.

During the extensive site testing carried out for Robust Detail classification all 30 of the impact and airborne tests had to achieve a minimum 5dB improvement over regulation requirements to gain this status. Due to this excellent performance record any site that registers the E-FC-14 system with Robust Details is automatically awarded 3 Code for Sustainable Homes Credits.

As part of the E-FC-14 registration Thermal Economics provide site training to Site Managers and Screeders by experienced industry professionals who will instruct on installation procedures and answer any questions regarding your specific project.

The E-FC-14 system can also be, and is frequently, used in non Robust Detail specifications, subject to pre-completion testing.