How to fix Warm Roof Fixings for Pitched Roofing

What is a warm roof?

This term refers to the roof structure that is insulated AT or ABOVE the pitched rafter level (as opposed to the horizontal ceiling joist level). Warm roofing is usually found forming part of a complete insulating envelope that is designed to encompass the building’s main structure.

Why insulate above rafters?

Buildings need to be thermally efficient and the performance requirements for these buildings are constantly increasing. Applying a single, uninter­rupted layer of sealed above-rafter insulation helps to meet stricter u-value targets. The lowered thermal conductivity delivers a reduction in heating costs and also lowers emissions.

What other benefits are there?

Lost spaces can easily be converted to living space without increasing plot size and all services in that area will be protected from freezing without the need for extra ventilation. Condensation is alleviated by the warm roof structure, which locates the dew-point further out of the building.

How is insulation fixed on a pitched warm roof?

We recommend Super-7™ warm roof fixings. These helical fasteners are self-tapping and securely fix counter battens to rafters, sandwiching the insulation between. Helical Super-7™ nails, manufactured by Thor, are engineered with the most precise pitch accuracy, easing driving and reducing the chance of buckling.

The Super-7™ Guide Tool is designed to overcome skew fastening deficiencies and improve build quality. The spiral nail is guided through a layer of insulation, vertically into the central part of the rafter, giving a highly professional result. The single layer process replaces the need for dual-layer systems, which are less efficient and more labour intensive to install (up to 66% less nailing is required).­

How many fixings will ensure all loads are safely carried?

This depends on the building’s individual details, as well as on the location of the building and its consequent exposure level. Many loads must be taken into consi­dera­tion, such as compressive (from roof weight and possibility of snow), tensile (from wind suction) and sliding (from a combination of compressive load, roof angle and insulation depth. Working out the right number of fixings can be easily done with the HeliCalc™ software co-sponsored by Twistfix and available on our website.

The software will select appropriate fixing length and density using BRE-approved design methods, calculating to take wind and snow loads into account to adhere to  BS6399 Part 2 & Part 3. National Annexes to Eurocodes 0 and 5 apply partial safety factors in respect of timber connections, dead loads, wind loads and snow loads. Please note that all results from this software apply to genuine Thor Super-7 fixings.

How do I fix Warm Roof Fixings?

1. LOCATE the batten above and at right angles to the rafter, applying body weight to press the batten tightly against the insulation material
2. POSITION the tool on the batten
3. FEED the super-7 nail directly into the bore, adjusting the tool setting and using the spirit level to align the nail on a totally vertical plane
4. NAIL the helical fixing through the batten, down to the top of the tool
5. REMOVE tool and drive the spiral fixing until it meets flush with the top of the counter batten.

Warm Roof Fixing - Product specifi­­cati­­on

Related documents:

How to fix warm roof insulation

How to fix insulated decks to flat roofs

Related links

• Visit Product Pages for Roof Insulation & Gutter.
• See all How-to Guides