Our step-by-step guide will walk you through the process of installing K-Roc Rainscreen Slab, including:
- the tools you will need
- how to prepare for installation
- the thickness of insulation you will need
- how to cut & fix the insulation
- finishing.
Rainscreen façades are a popular choice for mid- and high-rise developments. K-Roc Rainscreen Slab provides a versatile insulation solution for these applications. The rock mineral fibre slabs achieve a thermal conductivity of 0.034 W/mK and have a Euroclass A1 rating.
When fitting this insulation, it is important to be aware that all rainscreen façade systems are proprietary and use a range of fixing approaches to support the external façade. Similarly, the underlying structure may use steel or concrete framing, or a combination of the two. In this article, we look at best practice when installing K-Roc as part of a typical ventilated rainscreen with aluminium cladding on a steel frame construction, however, it is important to refer to the rainscreen system provider for specific installation guidance on each project.
Tools you will require
- Hard steel blade saw
- Dust mask
- Impact driver or SDS drill
- Suitable mechanical fixings and support anchors
Preparation
Prior to installing the rainscreen insulation, the steel framing system (SFS) should have been fixed and levelled with a suitable insulation, such as K-Roc Framing Slab fitted snuggly between the studs with no gaps. A vapour control layer should typically be fitted internally, followed by the drylining.
Externally, a cement particle board is fixed to the SFS followed by a breather membrane and weathering seals. Helping hand / support brackets for the outer cladding are then fitted either using c-channel or directly to the SFS studs. Cavity barriers should also be fitted both vertically and horizontally in line with the Building Regulations.
U-value calculation
If you need to confirm the thickness of K-Roc Rainscreen Slab and K-Roc Framing Slab to achieve your project U-value, our experienced technical service department can carry out the calculation and condensation risk analysis.
Installing the insulation
The K-Roc slabs should be installed in a break bonded pattern so that horizontal joints are offset. The slabs should lightly butt against one another with no gaps between the adjoining slabs or the slabs and the substrate.
Cutting
The slabs should be cut neatly to fit around fixings, brackets and junctions with care taken to ensure there are no gaps in the insulation layer. This can be done with a standard hard steel blade saw. When cutting the insulation, workers should also wear dust masks in line with CDM Guidance.
Fixings
The slabs should be secured with suitable metal mechanical fixings with polypropylene support anchors/washers. A minimum of three fixings per m2 should be fitted. The centre fixing of each slab should be metal with metal spreader plate. The remaining 2 fixings and spreader plates can be plastic if required. Fixings should have a minimum head diameter of 70 mm.
The type and number of fixing may vary depending on a range of factors including:
- location
- local topography
- the height and width of the wall
- the wall structure and cladding system
- the type of support system used to attach the cladding.
For this reason, the fixing requirements should always be assessed in accordance with BS EN 1991-1-4: 2005 + A1: 2010.
In all cases, the fixings should be evenly spaced across the rainscreen insulation.
For standard sheet metal cladding, fixings and further guidance can be obtained from Ejot or SFS. Where a masonry façade is used, a suitable restraint system, such as the Ancon 25/14 Restraint System, should be installed in line with their guidance.
Daily practice
At the end of the working day or during extended interruptions, the slab edges and joints should be protected.
Installation of the outer cladding should be scheduled so that the slabs are left exposed for the shortest possible time. If the slabs are exposed to wet conditions, then they should be allowed to dry as much as possible and properly inspected so that any damaged or saturated slabs can be replaced.
Storage
Where possible, K-Roc slabs should be stored inside a building. Where this is not possible, they should be stacked clear of the ground and covered with a suitable opaque polythene or weatherproof tarpaulin.
Outer cladding installation
Once the insulation layer is fitted and secured, T and L sections are typically fixed to the supporting brackets. The outer cladding can then be secured in line with manufacturer guidance.
Further guidance
If you have further questions about installing K-Roc Rainscreen Slab, refer to the product literature or contact our experienced Technical Service Department.
