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A pitched roof of timber rafters with tiles or slates on battens and Knauf Breatheline. Insulated with Polyfoam Pitched Roofboard laid over rafters and Polyfoam Raftersqueeze fitted between rafters.

A timber stop rail is fixed to the ends of the rafters. Polyfoam Pitched Roofboard is fitted starting from the timber stop rail, with all boards tightly butted.

The board is not suitable to be walked on, as defined in HSE33, except when covered with supporting timbers.

Knauf Breatheline, breather underlay, is pulled taught and laid directly over the insulation. 50 x 32mm counter battens are nailed through the Knauf Breatheline and Polyfoam Pitched Roofboard 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.

Once Polyfoam Pitched Roofboard is fixed in place, Polyfoam Raftersqueeze is pushed up between the rafters. If rafter centres are other than 600mm (eg 450mm, 300mm etc) cut the board slightly oversize to fit and use the remaining squeeze on one edge to push fit between rafters. They should be pushed up to the underside of the Polyfoam Pitched Roofboard, so there are no gaps. A timber batten or noggin fixed into the rafter below the Polyfoam Raftersqueeze can be used to hold the board in position.

There is an alternative fixing method for counter and tiling battens which is described in the BBA Certificate.

Polyfoam Pitched Roofboard 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.

Typical U-Values (W/m²K) of pitched warm roofs insulated with Polyfoam Pitched Roofboard and Raftersqueeze

Insulation between rafters	Thickness (mm)	U-Values (W/m2K)
		Polyfoam Pitched Roofboard thickness over rafters (mm)
		35	50	60
Polyfoam Raftersqueeze	150 (75+75)	0.17	0.16	0.15
	125 (75+50)	0.20	0.18	0.17
	100 (50+50)	0.23	0.21	0.19
	75	0.28	0.24	0.22

Note: Rafters assumed to be 38mm wide at 600 centres (6.3% bridging)..The U-Values have been calculated to BS EN ISO 6946: 1997

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: 1958. The underside of the rafters should be faced with 12.5mm plasterboard to provide fire protection.

Compression resistance

The rigidity of Polyfoam Pitched Roofboard makes the board easy to handle and less prone to site damage than less robust materials.

Moisture resistance

Polyfoam Pitched Roofboard is highly resistant to moisture absorption and will perform as stated if exposed to condensation or other moisture in use.

 

Polyfoam Pitched Roofboard is 3rd party certified by the British Board of Agrément.