High performance timber fixing for pitched warm roof construction

Helifix InSkew

InSkew is a high performance, stainless steel, self-tapping helical fixing for secure timber counter battens, through insulation, in pitched warm roof constructions.

Click here to use the Inskew Calculator

Designed specifically for use in warm roof construction, high performance InSkews are hammer or power driven through battens, counter battens and insulation, without affecting its thermal properties, and into the rafters. Their self-tapping design produces excellent holding power in both tension and compression and they are structurally more reliable, due to their helical profile, and more economical than traditional nails as far fewer are required.

Building Regulations Part ‘L’ Compliance

Since the publication of Building Regulations Part L, 2006, the new ‘u’ values for pitched warm roofs, where the insulation is above the rafter, is 0.18 – 0.20 W/m2K. Warm roofs, used to maximise living space and constructed using InSkews, have been shown to comply with these latest Part L Building Regulations.

Warm Roof Benefits

  • Compliance with Building Regulations – Part L
  • Reduces heat loss and retained heat gain
  • Lagging of pipes and tanks eliminated
  • Reduces running costs
  • No cold bridging
  • Protection against damp and corrosion
  • Roof tile ventilation no longer required
  • Produces a Room-in-a-Roof space
  • Slim, self-tapping, helical stainless steel fixing
  • Complies with Building Regulations Part L
  • Recommended by leading insulation manufacturers
  • Structurally more reliable and economical than traditional nails
  • High performance – fewer fixings required
  • Excellent holding power in both tension and compression
  • Hammer or power driven, normally without pre-drilling
  • Designed to withstand the structural loads – both the roof weight and wind suction
  • Prevents compression of insulation and does not impair its thermal performance
  • Self-tapping action avoids batten bouncing and splitting of timbers
  • Headless, flush fixing for minimal cold bridging and heat transfer
  • Rapid, free, in-house design service available
  • Written specifications covered by Helifix Professional Indemnity insurance
  • Full technical data available; Independently tested by TRADA

InSkew 600

  • 6mm outside diameter
  • 3.35mm core diameter
  • Austenitic stainless steel
  • Cold rolled from wire with a Hi-Fin special profile around a central core
  • Section provides good tensile and compressive characteristics
  • Available from stock in standard lengths from 75mm to 300mm
  • Manufactured to ISO 9001:2000 quality assured standards


1. UK mainland, not coastal or western Scotland.

2. Laid weight of tiles is less than or equal to 60Kg/m². These figures are for guidance only – please call Helifix for a detailed specification.

InSkew Length: The InSkews require a minimum 35mm penetration into a softwood rafter.

Additional Advice

A. Counterbattens must be at least 25mm thick to grip the tile batten fixing firmly.

B. Insulation over 50mm thick requires a stop batten.

C. Hand or power support tools should be used with InSkews of 120mm or longer. The power driver speeds installation and is recommended for deep insulation and to reduce buckling when driving into hard rafters.

D. When using InSkews to fix tile battens to support vertically hanging tiles, contact the Helifix Technical Sales Team.

InSkew Specification

Helifix was the first manufacturer to have had independent testing carried out on its roof fixing. Initially TRADA carried out comprehensive testing and developed our original load tables. These were updated in 2000 to conform to current timber standards and measure performance with deep insulation.

In 2003 Napier University conducted timber pull-out tests which concluded that three traditional fixings would be required to match the performance of a single InSkew. Comparative costs should bear this in mind – together with the labour costs of installing three times as many traditional fixings.

As insulation thicknesses increase so does the need for ever longer effective fixings. Whereas nails increase in diameter and tend to curve as their length increases, InSkews remain constant in diameter and are straight. Traditional fixings will therefore require wider, and more expensive, counterbattens and rafters as their length increases to avoid splitting the timber – a problem InSkews avoid with their self-tapping helical design.

Individual project specifications

Helifix is happy to provide individual project specifications to suit your exact requirements. You can either complete the InSkew 600 Enquiry Form on-line, or you can telephone our Technical Sales Team on 020 8735 5200.

Please make sure you can provide the following information to enable us to work out an accurate specification.

  1. Counter-batten thickness
  2. Insulation thickness
  3. Additional material thickness (e.g. ply deck)
  4. Counterbatten/rafter centres
  5. Roof pitch (rounded to the nearest 10°)
  6. The laid weight of tiles or slates being used
  7. In which county is the site?
  8. Wind exposure – minimum, medium or maximum?
  9. Is the building over 15m high?
  10. The area of the roof in m²

For a detailed and accurate fixing specification that takes into account your exact roof details and specific location, which will save you time and money and is covered under the Helifix Professional Indemnity insurance, please call our Technical Sales Team on 020 8735 5200.

The InSkew 600 is used as a structural batten fixing, normally being fixed through the counter-batten, the insulation sarking and then a minimum of 35mm into the rafters.

The density of fixing (the number of fixings per m²) must be enough to resist both the wind suction & the sliding load.

Occasionally the InSkew 600 is fixed through the tile-batten; in this case please phone the Helifix sales office for advice.

Tel: 020 8735 5200

Click here to use the Inskew Calculator