What is a zoomlat?
A zoomlat (literally “hem batten”) is a Dutch building term for a batten fixed along the edge of an object or building component. The word describes a function rather than a fixed size or timber species. You come across it in a few specific meanings.
Meanings
- At a valley gutter: a batten on each side of the valley, on which the tiles or slates alongside the gutter rest. The zinc of the gutter is turned up slightly at the edge and clamped between the zoomlat and the valley board. A lead flashing can be dressed over the zoomlat and the zinc, running under the tiles. The zoomlat lifts the roof covering slightly along the gutter, so it fits well and sheds water into the valley. In English this batten is comparable to a tilting fillet.
- At a hip or ridge: a batten along the hip rafter or ridge, to which the supports for the hip or ridge tiles are fixed.
- On a windmill: the batten on the sail around which the sailcloth is rolled up.
Why a zoomlat?
- Support: the tiles or slates along the gutter get firm support at the right height.
- Weathertightness: because the turned-up gutter zinc is clamped behind the zoomlat, water cannot run under the roofing and into the building.
- Straight line: a straight zoomlat gives a neat line where the roofing meets the valley or hip.
Practical points
- Durable timber: the zoomlat sits in a damp spot. Use treated or naturally durable timber.
- Zinc movement: do not clamp the zinc so tightly that it cannot expand. Use clips where needed.
- During renovation: when renewing a valley gutter, also replace a rotten zoomlat, as many leaks start there.
Related terms
- Hem on metal roofing
- Valley gutter
- Hip rafter
- Ridge tile
- Windmill
Want to learn more about construction terms? Visit our knowledge base at fredsdiyplans.com.