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Double lock standing seam

Main features

  • Proven, versatile system for roofing flat, curved and ‘free-form’ roofs.
  • Weather-tight down to 7º of pitch, 3º if seams are sealed..
  • Discrete joints give a light, elegant appearance.
  • Modern profiling and seaming machines facilitate short installation times.
  • On-the-roof detailing uses folding techniques or soldered joints – no mastic!
  • Items such as snow guards and life line attachments are readily available.
joint debout

Basic system information

1. elZinc® Standing seam roofing tray, nominal max. length 10m.
2. Standing seam joint (normally follow line of maximum pitch)
3. Expansion gap at seam base
4. Seam centres dimension. Normally from 430 to 600mm
5. Stainless steel ‘fixed’ clip – anchors the tray in position
6. Stainless steel ‘sliding’ clip – allows longitudinal expansion
7. Self-expanding sealing strip for roofs pitched under 7º

The standing seam joint

The joint requires 70mm of material to make.  It is formed by seaming together profiled trays of zinc as illustrated below.

Standing seam tray

Clipped undercloak and the overcloak

Small gap at base forms automatically and allows for lateral thermal expansion

First turn completes angle standing seam joint

Second turn completes double lock standing seam joint

Cross joints

Transverse joints vary according to roof pitch.  They are needed to introduce expansion joints on large roofs or around details.


The system is installed across the roof in either direction, or preferably outwards from a centrally placed undercloak – undercloak tray that ensures trays of equal width (and therefore symmetry) at both ends of the roof.

Dimensioning and fixing

If the length of the roofing trays is over 1,5m the clips used to secure them to the substrate must allow the zinc to expand and contract, and these trays use a combination of fixed clips and sliding clips to accomplish this.

The position of the fixed clip zone depends on roof pitch – to avoid the trays from buckling, the steeper the pitch, the higher the anchoring band of fixed clips is positioned.  The thermal movement generated in the trays is accommodated by a gap introduced in the detail at the foot and at the head of the trays.

The standing seam, angle seam and flat lock panel systems all use the same set of seam centres, which are tied into commercially available coil widths.  Therefore, the following table can be used to determine the bay widths, thicknesses, and also to specify the number of fixings per m2 for each of these systems.

The following table can be used to determine :

  • The bay widths and thicknesses
  • The number of fixings per m2 for each of these systems

System dimensioning

System dimensioning Fixing requirements – Number of clips per m2/clip centres in cms related to building height
< 8m8m < H <= 20m20a 100m
ThickBay width Centre Edge CornerCentre Edge CornerCentre Edge Corner

*Notes:  Assumes a nominal clip pull out load of 560N. Valid for non-exposed locations.

Various factors affect wind uplift – (location, exposure, orientation and roof geometry) and advice should be sought from elZinc® when determining tray widths for projects in exposed locations.  This is not only to ensure that the cladding does not suffer during storms, it is also to avoid fluttering of the trays during periods of continuously windy weather.

Bay widths may be narrowed to the next standard width in order to reduce quilting in the sheets if a flatter appearance to the cladding is required, especially for wall cladding or steeply pitched roofs.


Find out our wide selection of architectural details for the most commonly used systems.

Double lock standing seam