How to fix Warm Roof Fixings for Pitched Roofing

What is a warm roof?

A warm roof is a roof structure that is insulated at or over the pitched rafter level rather than at or over the horizontal ceiling joist level. Warm roofing usually forms part of an insulating envelope that encompasses the main structure of the building.

What are the benefits of insulating above the rafters?

As the performance requirements for thermally efficient buildings increase, the application of a single unin­­ter­­rup­­ted and sealed layer of over-rafter insulation helps to meet ever more stringent u-value targets. The effective design of warm roof insulation offers many advantages to the homeowner.Low thermal conductivity results in lowers heating costs and emissions.

  • Loft spaces can be designed and utilised to accommodate additional living space without increase in plot size.
  • Services in the loft areas are protected from freezing.
  • No need for complicated ventilation.
  • The warm roof structure moves the dew-point further out of the building to alleviate conden­­sati­­on.

How is the insulation fixed on a pitched warm roof?

Super-7™ Warm Roof Fixings are used in over-rafter pitched warm roof construction.  The self-tapping helical fasteners secure counter-battens to rafters with a layer of insulation sandwiched between. Thor Helical Super-7 nails are engineered with a patented precise pitch accuracy to ease driving and alleviate buckling.

The patent pending Super-7 Guide Tool overcomes the technical and practical deficiencies associated in skew fastening. ­ It improves build quality by guiding the spiral nail through deep insulation layers and vertically into the central section of the hidden rafter. Improved warm roof build quality enables single layer of deep over rafter insulation and eliminates the need for less efficient and labour intensive dual-layer systems.

  • Improved build quality.­Labour savings – up to 66% less nailing.
  • Suitable for up to 150mm deep insulation

How many fixings should I be using to ensure all loads are safely carried?

The length and density of the warm roof fixing system depends on the location and exposure of the building and the building details itself. The system is required to take; compressive load from roof weight and snow potential; tensile load applied by wind suction; and sliding load, which is a function of the compressive load, angle of roof pitch and the depth of insulation between rafter and counter-batten.

Fortunately, Twistfix is a co-sponsor of the HeliCalc Project. HeliCalc™ software selects the appropriate fixing length and density using a BRE approved design method to calculate wind & snow loads in accordance with BS6399 Part 2 & Part 3.

National Annexes to Euro-codes 0 and 5 apply partial safety factors in respect of timber connections, dead loads, wind loads and snow loads.

The results of HeliCalc software are specific to genuine Super-7 fixings only.

  • BRE Approved Design Method.­Inde­­pen­­den­­tly tested.
  • Meets the requirements of the NHBC


  • Where 80-150mm deep insulation is used the robust Super-7™ warm roof nail enables fixing densities to be reduced by up to 66% compared to traditional 6mm helical nail systems.
  • The result offers an overall reduction in thermal bridging potential and significant labour savings by virtue of reduced nailing.

How to fix Warm Roof Fixings

  1. Locate batten directly above & per­­pen­­dicu­­lar to the rafter and apply body weight to hold batten tightly against insulation.
  2. Position tool on batten.
  3. Feed Super-7 helical nail into bore & adjust tool’s seating, using its bubble level to align spiral nail upon a vertical plane.
  4. Nail helical fixing through batten & down to top of tool.
  5. Remove tool & drive spiral fixing until flush with the top of the counter-batten.

Warm Roof Fixing - Product specifi­­cati­­on


  Super-7™ Warm Roof Batten Fixing


  130mm - 240mm in 10mm increments



  Cross Sectional Area:


  Ultimate Tensile Strength: 



  Austenitic Stainless steel - (304)

  Pitch Deviation on Tie:

  < 0.5%*

Related documents:

How to fix warm roof insulation brochure How to fix warm roof insulation

How to fix insulated decks to flat roofs brochure How to fix insulated decks to flat roofs

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