Rocksilk Krimpact Flat Roof Slabs and Rocksilk Krimpact Cut-To-Falls are suitable for use on all types of roof deck. The insulation boards are laid over and fully bonded to a vapour control membrane which is bonded to the roof deck. The insulation is overlaid with a waterproof membrane consisting of either a fully bonded built-up bitumen roofing system, or mastic asphalt. When used with mastic asphalt, the insulation is overlaid with 12mm bitumen impregnated fibreboard and an isolating felt. The boards are not suitable for the direct application of torch-on roofing felts.

Rocksilk Krimpact Cut-To-Falls boards are supplied clearly marked with a laying scheme for their application. Rocksilk Krimpact Cut-To-Falls is not just a product but a comprehensive service from design to delivery. Knauf Insulation will normally survey existing roofs prior to producing the Cut-To-Falls scheme but can also do so from scale drawings.

Timber decks

The vapour barrier can be either nailed to the timber deck as defined in BS 8217: 1994, or bitumen bonded using traditional techniques. Hot bitumen is mopped over the vapour control layer and the Rocksilk Krimpact Slabs bedded into place as the work proceeds.

Built-up felt membranes

High performance bitumen membrane systems are fully bonded in hot bitumen to the Rocksilk Krimpact Slabs using traditional roll and pour methods. Rocksilk Krimpact Slabs are not suitable for the direct application of torch-on roofing felts.

Mastic asphalt surface

Rocksilk Krimpact Slabs provide a stable base for mastic asphalt. The boards should be overlaid with a 12mm layer of bitumen impregnated fibreboard. A bitumen felt (low grade is satisfactory) should be loose laid without bonding onto the fibreboard prior to the application of two layers of mastic asphalt.

Thermal performance

The thermal conductivity of Rocksilk Krimpact Flat Roof Slab is 0.038 W/mK. The thermal conductivity of Rocksilk Krimpact Cut- To-Falls is 0.038 W/mK. The table gives U-Values for typical constructions insulated with Rocksilk Krimpact Flat Roof Slab products. It can be used to determine which combination will satisfy the Building Regulations U-Value requirements for flat roofs.

Typical U-values (W/m²K) of flat roofs insulated with Rocksilk Krimpact Cut-To-Falls

Minimum thickness (mm)	U-values (W/m2K)
	19mm chipboard, timber joists, 12.5mm plasterboard	Profiled metal deck	150mm concrete, 40mm screed, 13mm plaster
180	0.19	0.20	0.19
170	0.20	0.22	0.20
160	0.21	0.23	0.22
150	0.22	0.24	0.23
145	0.24	0.26	0.24

Note:The figures in this table assume a bitumen felt membrane. For project specific calculations please contact our Techincal Advisory Centre on 01744 76 66 66.

Fire performance

All Rocksilk Krimpact Flat Roof Slab products are classified as A1 to BS EN ISO 13501-1. The rock mineral wool in Rocksilk products has an extremely high melting point of over 1000°C. In the event of fire they will emit negligible quantities of smoke and fumes. The heat emission from the products is insignificant.

Mechanical strength

Rocksilk Krimpact Flat Roof Slabs are strong enough to be used for normal foot traffic during installation and further occasional maintenance for roof inspection. The slabs have good free spanning and cantilever capabilities which make them practical to install.

For specific walkways, protection is required to spread the expected loads, for example, using walkway plates. For specific advice, the waterproofing membrane manufacturer should be consulted.

 

• Significantly improves accoustic performance of timber and metal decks
• Non-conbustible product with Euroclass A1 rating
• Supported by specialist design service and installation advice
• Bespoke system designed to meet the needs of each individual project. Contact Knauf Insulation for details