OVER JOIST (EXTERNAL)

How To Install

Over Joist (External) Flat Roof Installation

Apply SuperFOIL directly from the roll, on the internal joist face, horizontally starting at the external wall. Staple the start of the roll into place on to your joist and then continue to roll the product out across the joists.

Whilst fitting SuperFOIL, you should hold the product taut whilst stapling into place. Staple through the product into the joists at approximately 50mm-100mm intervals using the correct size staples (see chart). Once you have finished a length, simply cut to the correct size and then continue onto fixing the next layer with a minimum of a 50mm overlap. Ensure secure fixing by stapling the insulation onto the joists where the joint crosses. 

Seal all joints, tears and cuts with SuperFOIL 100mm tape, paying special attention around any penetrations through the insulation to ensure an air tight finish. 

Finish your installation by fixing counter battens on top of the insulation horizontally (maximum of 600mm centres) to allow an adequate air space. Attach your external finish to battens, following the manufacturer’s guidelines.

Surrey-Roofing-Flat-Roof-3
ProductMinimum Batten SizeStaple Size Required
SF19+38mm20mm
SF4050mm30mm
SF6063mm40mm

Ideal Products For External Applications

SFBB-2

SuperFOIL SFBB

  • 0.29 R VALUE

    R Value of 0.29 When used in a roof

  • 1mm THICK

    1.5m Wide by 25m Long

SF19BB-Roll-Laid-Down

SuperFOIL SF19BB

  • 2.22 R VALUE

    R Value of 2.22 When used in a roof

  • 40mm THICK

    1.2/1.5m Wide by 10m Long

SF40BB-Roll-Laid-Down

SuperFOIL SF40BB

  • 3.67 R VALUE

    R Value of 3.67 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 Flat Roof Diagram
SuperFOIL Product Below Rafters SuperFOIL Product Above Rafters
No Additional Insulation SF19BB SF40BB
No Additional Insulation N/A 0.40U 0.27U
SF19+ 0.33U 0.20U 0.15U
SF40 0.25U 0.17U 0.13U
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 0.40U 0.33U 0.28U 0.25U 0.20U 0.18U 0.17U 0.16U 0.15U 0.14U 0.14U 0.13U 0.12U
SF40BB 0.27U 0.24U 0.22U 0.20U 0.18U 0.16U 0.15U 0.14U 0.13U 0.13U 0.12U 0.11U 0.11U
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 0.40U 0.32U 0.27U 0.24U 0.21U 0.19U 0.17U 0.16U 0.14U 0.13U 0.13U 0.12U 0.11U
SF40BB 0.27U 0.24U 0.21U 0.19U 0.17U 0.16U 0.14U 0.13U 0.12U 0.12U 0.11U 0.10U 0.10U
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 0.40U 0.31U 0.26U 0.23U 0.20U 0.18U 0.16U 0.15U 0.13U 0.13U 0.12U 0.11U 0.10U
SF40BB 0.27U 0.23U 0.20U 0.18U 0.16U 0.15U 0.14U 0.13U 0.12U 0.11U 0.10U 0.10U 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 0.40U 0.29U 0.24U 0.20U 0.17U 0.15U 0.14U 0.12U 0.11U 0.10U 0.10U 0.09U 0.08U
SF40BB 0.27U 0.22U 0.19U 0.16U 0.14U 0.13U 0.12U 0.11U 0.10U 0.09U 0.09U 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 0.40U 0.29U 0.23U 0.19U 0.16U 0.14U 0.13U 0.12U 0.11U 0.10U 0.09U 0.08U 0.08U
SF40BB 0.27U 0.22U 0.18U 0.15U 0.14U 0.12U 0.11U 0.10U 0.09U 0.09U 0.08U 0.08U 0.07U

FIXING DETAILS

Roof Windows

Roof Windows

Install SuperFOIL using the correct method for your application.
To finish installation around roof 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 Butyl tape or other suitable double-sided waterproof tape.

Vents,Ducts & Penetrations

Vents,Ducts & Penetrations

At penetrations such as vent ducting, pipework etc, SuperFOIL should be trimmed to ensure there are no gaps around the penetration.
Using SuperFOIL Butyl Tape or other suitable waterproof 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.

UNSURE WHERE TO START?

Our FREE guide gives you all the information on saving time and money when insulating your home, and how to really make a difference to the comfort of your rooms.

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