7.2 Pitched roofs

Also see:

3.3

7.2.17 Battens

Battens and counter battens shall be adequately sized, spaced and fixed to support the roof covering.

Battens and counter battens should be:

  • in accordance with BS 5534, accompanied by a delivery note and indelibly marked with the supplier, origin, grade and size
  • preservative treated and not re-sawn, ripped or planed after treatment (battens can be cut to length)
  • where cut ends are located in wet or dry verges, treated with preservative
  • cut square, butt jointed over rafters and nailed to each rafter they span
  • fixed by skew driven nails on each side of a joint.

Counter battens should be fixed to the rafters and not only to sarking sheets or boards. The dimensions of counter battens should also be sufficient to provide a ventilation gap (where required) and permit a drainage pathway beneath the battens.

Battens should be:

  • a minimum of 1.2m long and span a minimum of three rafters
  • set out in straight lines parallel to the ridge and to the gauge required for the tile or slate (the lap should not be decreased as this would reduce weathertightness)
  • set out so that the tiles project a minimum of 50mm over the gutter
  • fixed through counter battens to rafters
  • where on sarking sheets or boards, be supported on counter battens
  • at verges, tile battens should finish 25mm-50mm from the face of the protecting undercloak
  • sized in accordance with the roof covering/solar roof panel manufacturer’s recommendations, but not less than shown in Table 18.

Table 18: Minimum batten sizes

Notes

1. Tolerances on the basic sizes of timber battens should be: width ±3 mm, depth −0 +3 mm.
2. Batten sizes may need to be increased, where solar roof panels are installed, to ensure full fixing depth penetration is achieved.

Battens should be set out to avoid joints occurring over the same rafter. Where batten spacing is:

  • more than 200mm, no more than one batten in any group of four should be joined over any one truss or rafter, see Figure 60
  • 200mm or less, no more than three joints should be made over any twelve consecutive battens, see Figure 61.

Batten fixings should be capable of resisting wind forces in accordance with BS 5534 (Annex H.7 ‘Batten fixing penetration’). The length, type and material specification of the fixing to be used, should be determined according to the site exposure and location.

Nails for fixing battens and counterbattens, should meet the following minimum requirements:

  • be a driven nail of a minimum of 3.35mm diameter with 40mm minimum penetration into the supporting structure
  • a mechanical gun nail with a shank diameter not less than 3.1mm
  • round plain shank, indented, spiral roll or annular ring shank nails maybe selected (ring shank nails are recommended in Scotland and Northern Ireland)
  • zinc-coated in accordance with BS EN 10230‑1
  • hot dip galvanised steel or aluminium when situated in a coastal location.

Nails should not be driven below the top of the batten, this reduces the thickness of timber between the nail head and the underside of the batten, which reduces the pull-off resistance and may damage the batten.

Last updated: 2nd January 2024

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