What is a batten roll roof?
A batten roll roof is a metal roof in which the bays are turned up against timber battens and the joints are covered with metal caps: the rolls. It is one of the two classic systems for zinc, copper and lead work on pitched roofs; the other is standing seam, where the bays are welted together without a batten. In Dutch the roof is called a roefdak or roevendak.
You can spot a batten roll roof immediately by the regular, strongly projecting vertical ribs across the whole roof slope, with a flat field between them. It gives a roof a pronounced, craft-made appearance, which is why it is favoured on dormers, bays, turrets, extensions, conservatories and in restoration work.
How it is built up
- Roll battens running down the fall, typically at centres of about 500 to 600 mm. On monopitch roofs 500 mm is often adopted in practice.
- Metal bays between them, turned up against the batten on both sides.
- Clips holding the bays to the decking while still allowing the metal to slide.
- Roll caps over the battens, secured to the upstands on both sides.
- Head details at ridge, eaves, valley and abutments, with provision for movement along the length.
Requirements and rules of thumb
- Pitch — manufacturers state the system is usable from about 3°, but it performs demonstrably better from 7° upwards. The shallower the roof, the more critical the ridge and eaves detailing.
- Material thickness — 0.7 to 0.8 mm is normal for zinc roofing; 1.0 mm for larger areas or heavier loading.
- Bay length — there is a limit to the length of a continuous bay, because thermal movement otherwise becomes too large. Longer slopes are divided with a movement step.
- Ventilation under the decking — this is where zinc roofs most often fail. Zinc lying in trapped moisture on its underside corrodes from below. Provide a continuous ventilated void, or use a system explicitly approved for unventilated (“warm roof”) use.
- No mixed metals — never drain copper onto zinc.
Batten roll or standing seam?
A standing seam roof looks flatter and, with a double welt, is the usual choice at very low pitches. A batten roll roof has a stronger profile, is a little more robust underfoot and is chosen for its ribbed appearance. Both are specialist work: welting, folding and soldering demand tools and practice that most DIY builders do not have.
| Standing seam | Flatter look; with a double welt, the usual choice at very low pitches |
|---|---|
| Batten roll | Stronger profile, a little more robust underfoot, chosen for its ribbed appearance |
Related terms
- Roll cap
- Roll batten
- Zinc
- Roof boarding
- Batten
Want to learn more about construction terms? Visit our knowledge base at fredsdiyplans.com.