Over Rafter
(External)

From simple insulation upgrades, meeting building regulations, or achieving Passivhaus standards. SuperFOIL can find you the perfect solution.

Laying Insulation on Hybrid Flat Roof

How To Install

Over Rafter (External) Pitched Roof (Counter Battened)

Two Builders Construction Wooden Frame for Roof
  • Apply SuperFOIL directly from the roll, on top of the rafters horizontally starting at the bottom of the rafters.
  • Staple the start of the roll into place onto your rafter and then continue to roll the product out across the rafters. Tension should be applied to the insulation whilst being fixed into place to ensure no draping of the product.
  • Staple through the SuperFOIL into the rafters at approximately 50mm-100mm intervals using the correct size staples (see chart).
  • Once you have finished a length, simply cut it to the correct size and fasten it into place before continuing to the next layer.
  • Place the built-in 50mm taped overlap over your previous layer and continue with the installation using the same method.

When finishing at the side edges of the roof, the external breather membrane layer should be folded back from the insulation layers, and the internal insulation layers should be trimmed back to the rafter timbers. The breather membrane should then be folded over the insulation layers to encapsulate the edge of the insulation material, and then be stapled into place on the rafter face. Doing this ensures to keep a watertight finish on your installation.

Check all overlaps are fully sealed and then attach the correct size battens (to provide adequate air space) in line with the roof joists, before attaching your tile batten in line with the manufacturer’s guidelines.

Over Rafter (External) Pitched Roof (Non–Counter Battened) 

  • Apply SuperFOIL directly from the roll, on top of the rafters horizontally starting at the bottom of the rafters.
  • Staple the start of the roll into place onto your rafter and then continue to roll the product out across the rafters. The SuperFOIL should be allowed to drape into the rafter void to create a 10mm gap between the top of the insulation and the underside of the tile batten. This will allow for any water that accumulates or penetrates the tiles to run down into your guttering.
  • Staple through the SuperFOIL into the rafters at approximately 50mm-100mm intervals using the correct size staples (see chart). Once you have finished a length, simply cut it to the correct size and fasten it into place before continuing to the next layer.
  • Place the built-in 50mm taped overlap over your previous layer and continue with the installation using the same method.

When finishing at the side edges of the roof, the external breather membrane layer should be folded back from the insulation layers, and the internal insulation layers should be trimmed back to the rafter timbers. The breather membrane should then be folded over the insulation layers to encapsulate the edge of the insulation material, and then be stapled into place on the rafter face. Doing this ensures to keep a watertight finish on your installation.

Once the insulation is in place, check to ensure that all overlaps are sealed fully. Finish installation by attaching tile battens in line with manufacturers' guidelines.

UK building site with scaffolding
Product Minimum Batten Size Staple Size Required
SFBB25mm10mm
SF19BB38mm14mm
SF40BB50mm30mm

Fixing Details

Install SuperFOIL using the correct method for your application.

Eaves Detail

At the eaves, the breather membrane should overlap with the eaves tray as required. To do this, separate the top woven layer from the rest of the insulation and fold it back onto itself. This allows for the remaining insulation layers to be cut and turned down to meet with the wall plate to create a continuous insulation envelope.

Unfold the separated breather membrane down, overlapping the eaves tray, and fasten it into place using the integrated overlap tape.

Ridge Detail

Complete both sides of the roof, leaving space on either side of the ridge to allow for a layer of SuperFOIL plus 100mm overlap on fitted layers. Roll out the SuperFOIL over the top of the ridge, ensuring that the product overlaps fitted layers by 100mm on both sides. Seal the overlap using SuperFOIL Butyl tape or waterproof double-sided tape to create a watertight finish. Follow instructions for ‘side laps’ if using multiple rolls over the ridge.

Side Laps Detail

In the case of two rolls meeting vertically ( side laps), the top woven breather membrane of the fitted roll should be folded back from the rest of the insulation layers. The remaining lower layers should then be cut back to the last rafter that is fully covered, leaving a minimum of 150mm of the breathable membrane to overlap the next roll to be installed. Seal the overlap using SuperFOIL Butyl tape or waterproof double-sided tape to create a watertight finish.

Skylights & Dormer Window Detail

To finish installation around skylights or dormer windows, simply trim the SuperFOIL up to the frame and staple the insulation to the surrounding framework where possible. Finish installation by sealing all joints with SuperFOIL 100mm Superior foil tape.

Sealing Penetrations Through SuperFOIL

At penetrations such as vent ducting, pipework etc, SuperFOIL should be trimmed to ensure there are no gaps around the penetration. Using 100mm SuperFOIL Butyl tape, or other suitable weatherproof double-sided tape, ensure the SuperFOIL is well sealed around the penetration to create an airtight barrier. This can be achieved by using small sections of tape and working around the penetration.

Valleys Detail

At the valley, the breather membrane should drape over the valley gutter. To do this, secure the product to the rafters using the correct size staple, ensuring to leave the section over the valley loose. Separate the top woven layer that is over the valley from the rest of the insulation and fold it back onto itself. This allows for the remaining insulation layers to be cut away from the breathable membrane. Unfold the separated breather membrane down, leaving the breather membrane in the valley. Continue with installation up the valley using the same method.

Hip Detail

At the hip, cut the SuperFOIL to cover the top of the hip timber with no overlap and staple it into place. On the other side of the roof, install SuperFOIL using the correct method. At the hip timber, separate the top woven layer from the rest of the insulation and fold back onto itself allowing for a 150mm overlap over the hip. Cut the remaining insulation layers leaving just the top breathable membrane. Unfold the separated breather membrane down and place this over the hip timber. Fasten securely into place using the correct staples. Seal the join using SuperFOIL Butyl tape or other suitable double-sided waterproof tape.

Ideal Products For External Applications

SFBB-SMALL

SuperFOIL SFBB

SuperFOIL-SF19BB-roll-SMALL

SuperFOIL SF19BB

SF40BB-Roll-Laid-Down-SMALL

SuperFOIL SF40BB

SuperFOIL SFBB

  • 0.29 R Value
    When used in a roof
  • 1mm Thick
    1.5m Wide by 25/50m Long

SuperFOIL SF19BB

  • 2.22 R Value
    When used in a roof
  • 40mm Thick
    1.2/1.5m Wide by 10m Long

SuperFOIL SF40BB

  • 3.67 R Value
    When used in a roof
  • 75mm Thick
    1.5m Wide by 10m Long

Choose Your Solution

Use the charts below to find the ideal combination of insulations for your project

External Pitched Roof Diagram
SuperFOIL Product internal SuperFOIL Product External
No Additional Insulation SF19BB SF40BB
No Additional Insulation N/A 0.41U 0.26U
SF19+ 0.34U 0.26U 0.20U
SF40 0.26U 0.17U 0.14U
SF60 0.20U 0.14U 0.12U
SuperFOIL Product Mineral Wool / Glass Fibre / Sheeps Wool - 0.044W/mK
No Additional Insulation 25mm 50mm 75mm 100mm 125mm 150mm 175mm 200mm 225mm 250mm 275mm 300mm
SF19BB 0.41U 0.34U 0.29U 0.26U 0.23U 0.21U 0.19U 0.17U 0.16U 0.15U 0.14U 0.13U 0.12U
SF40BB 0.26U 0.23U 0.21U 0.19U 0.17U 0.16U 0.15U 0.14U 0.13U 0.12U 0.12U 0.11U 0.1U
SuperFOIL Product Mineral Wool / Glass Fibre / Sheeps Wool - 0.037W/mK
No Additional Insulation 25mm 50mm 75mm 100mm 125mm 150mm 175mm 200mm 225mm 250mm 275mm 300mm
SF19BB 0.41U 0.33U 0.28U 0.24U 0.22U 0.19U 0.18U 0.16U 0.15U 0.14U 0.13U 0.12U 0.11U
SF40BB 0.26U 0.22U 0.20U 0.18U 0.16U 0.15U 0.14U 0.13U 0.12U 0.11U 0.11U 0.1U 0.1U
SuperFOIL Product Mineral Wool / Glass Fibre / Sheeps Wool - 0.032W/mK
No Additional Insulation 25mm 50mm 75mm 100mm 125mm 150mm 175mm 200mm 225mm 250mm 275mm 300mm
SF19BB 0.41U 0.33U 0.27U 0.23U 0.20U 0.18U 0.16U 0.15U 0.14U 0.13U 0.12U 0.11U 0.10U
SF40BB 0.26U 0.22U 0.19U 0.17U 0.16U 0.14U 0.13U 0.12U 0.11U 0.11U 0.1U 0.09U 0.09U
SuperFOIL Product PIR FOAM BOARD - 0.022W/MK
No Additional Insulation 25mm 50mm 75mm 100mm 125mm 150mm 175mm 200mm 225mm 250mm 275mm 300mm
SF19BB 0.33U 0.26U 0.22U 0.19U 0.16U 0.15U 0.13U 0.12U 0.11U 0.1U 0.1U 0.09U 0.09U
SF40BB 0.22U 0.19U 0.17U 0.15U 0.13U 0.12U 0.11U 0.1U 0.1U 0.09U 0.08U 0.08U 0.08U
SuperFOIL Product Phenolic FOAM BOARD - 0.019W/MK
No Additional Insulation 25mm 50mm 75mm 100mm 125mm 150mm 175mm 200mm 225mm 250mm 275mm 300mm
SF19BB 0.33U 0.26U 0.21U 0.18U 0.16U 0.14U 0.13U 0.11U 0.11U 0.1U 0.09U 0.09U 0.08U
SF40BB 0.22U 0.19U 0.16U 0.14U 0.13U 0.11U 0.11U 0.1U 0.09U 0.08U 0.08U 0.07U 0.07U
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