Polyfoam Sarking Board System/Polyfoam Pitched Roofboard/Raftersqueeze
Product Description
Warm roof: Insulation above and between rafters (2)
Polyfoam Sarkingboard System for the insulation of pitched roofs.
Products
- Polyfoam Sarking Board System is a high performance, 100% ozone friendly, extruded polystyrene, rigid board insulation system. It is lightweight and consists of a 75mm top hat section over the top of the rafters and Raftersqueeze, a flexible infill piece that fits between rafters, and allows for some variation in timber rafter centres.
- Knauf Breatheline is a breathable membrane with a polypropylene non-woven coating on both sides.
Typical Construction
A pitched roof of timber rafters with tiles or slates on battens and Knauf Breatheline. Insulated with the Polyfoam Sarking Board top hat section laid over rafters at 600mm centres and engaged by its rebated edges. Polyfoam Raftersqueeze is fitted between the rafters, immediately below the Polyfoam Sarking Board top hat section.
Installation
To ensure accurate setting out of the roof trusses, Polyfoam Sarking Board Top Hat section can be used as a template when erecting the roof structure.
The insulation boards are not suitable to be walked on, as defined in HSE 33, except when covered with supporting timbers.
A timber stop rail is fixed to the ends of the rafters which are then overlayed with the 75mm Top Hat section located over and between the rafters via the rebated edges. The insulation thickness over the rafters is 55mm.
Knauf Breatheline is pulled taught and laid directly over the insulation.
50 x 32mm counter battens are nailed through the Knauf Breatheline and Top Hat board and into the rafters using spiral fixings such as Helifix Inskew 600 or Buildex RG, with minimum penetration into the rafter of 35mm.
Tiling battens are laid across the roof and nailed into the counter battens. Tiles should be stacked so that they bear directly over the rafters. Finally, the roofing tiles or slates are fixed, to the manufacturer’s recommendations.
Working from the underside of the roof, the Raftersqueeze infill board is placed in position between the rafters. Raftersqueeze is fitted starting from the eaves with all boards tightly butted.
The underside of rafters to be lined with plain or foil backed plasterboard, as appropriate. If desired, the Raftersqueeze board can be fitted from above the new roof before the Top Hat section. Install timber supporting battens, taking care to leave 20mm between the Raftersqueeze and the top of the rafter for the rebated section of the Top Hat board.
There is an alternative fixing method for counter and tiling battens which is described in the Polyfoam Pitched Roofboard BBA Certificate 95/3097.
Performance
Thermal insulation
Polyfoam Sarking Board has a thermal conductivity of 0.029 W/mK. Polyfoam Raftersqueeze has a thermal conductivity of 0.030 W/mK. The table below gives U-values for typical constructions.
Moisture resistance
Polyfoam Sarking Board System is highly resistant to moisture absorption and will perform as stated if exposed to condensation or other moisture in use.
Fire performance
The boards contain a flame retardant specifically designed to inhibit localised ignition. The boards will melt if brought into contact with high temperature sources and are classed as combustible. However, the use of the boards will not affect the fire rating obtained by tiled roofs when evaluated by assessment or tested to BS 476: Part 3: 1975. The underside of the rafters should be faced with 12.5mm plasterboard to provide fire protection.
Compression resistance
The rigidity of the Polyfoam Sarking Board System makes the boards easy to handle and less prone to site damage than less robust materials.
Certification
Polyfoam Sarking Board is third party certified by the British Board of Agrément.
Advantages
- Top hat section enhances the rigidity of the roof
- Polyfoam is unaffected by moisture
- Polyfoam is lightweight yet very strong, making it easy to handle on the roof
- Raftersqueeze fits tightly to rafters
- Use Polyfoam Sarking Board as template for setting out rafters
Technical Information
Product LiteratureCurrently Unavailable