A "Robust Detail" solution for the acoustic insulation of masonry separating floors

Product

Rocksilk Acoustic Floor Slab Plus is a dense, rigid, non-combustible slab of rock mineral wool which is highly compression resistant.

Typical Construction

A precast concrete floor slab with a 65mm cement:sand screed and a floating floor of 18mm chipboard on 30mm Rocksilk Acoustic Floor Slab Plus. A ceiling of 15mm Knauf Standard Wallboard supported on the Knauf C Form II ceiling system.

The construction complies with Robust Detail E-FC-1 with FFT4 floating floor treatment.

No Post-construction testing is required, but the site must be registered with Robust Details Ltd and built strictly in accordance with their specification. A fee is payable to Robust Details Ltd and the site may be subject to spot visual checks from Robust Details Ltd inspectors and later acoustic testing.

Rocksilk Acoustic Floor Slab Plus is also suitable for Robust Details E-FC-2 and E-FS-1, as illustrated below.

Installation

The surface of any floor or screed should be smooth and flat within 5mm when measured with a 3m straight edge. When the screed has dried out, lay Rocksilk Acoustic Floor Slab Plus over the entire floor area. The joints between boards should be tightly butted. Lay the tongue and groove chipboard over the insulation and glue all joints. Install flanking strips around the perimeter of the flooring chipboard to isolate the boards from the walls and skirtings. No services should be installed in the floor system.

Performance

Acoustic performance

Rocksilk Acoustic Floor Slab Plus has excellent sound absorption characteristics. For optimum performance, the insulation must be tightly butted, with no gaps.

Fire performance

Rocksilk Acoustic Floor Slab Plus is classified as non-combustible to BS 476: Part 4: 1970.

Density

Rocksilk Acoustic Floor Slab Plus has a nominal density of 140 kg/m³.

Compression resistance

Rocksilk Acoustic Floor Slab Plus is manufactured to provide a very high level of compression resistance.

Advantages

• Wet screed or in-situ concrete helps to minimise airpaths through the floor
• Resilient layer provides good acoustic isolation to improve impact sound performance
• Independent ceiling provides acoustic isolation and void for services
• Rocksilk Acoustic Floor Slab Plus easily exceeds the laboratory test requirements of Robust Details Ltd for a resilient layer in these applications