Standing seam system


The double standing seam system provides a rain-tight roof and facade covering where the pitch is in excess of 3°, preferably 7°. (see fig. 1).

The double standing seam system makes it possible for a roof or facade to be covered with NedZink Zinc-Titanium quickly and at reasonable cost. This is because preformed metal bays are used, and the seams are folded mechanically, reducing manual folding to a minimum.

The preformed bays are supplied in standard sizes. The bays are secured to the substructure in question by means of fixed and sliding clips (see fig. 3).

The fixed clips secure the bays, and the sliding clips permit longitudinal movement. Please consult the section headed 'Assembly' for information on the required position of these clips.
The double standing seam system offers all the possibilities for connections and joints with other systems and building components.

The double standing seam system roof.

There are two ways of assembling the double standing seam system:

  • System 1 with pre-profiled side upstands
  • System 2 with straight side upstands

Both systems may be used for double standing seam roof. The choice of which system to use depends on the type of roof and the metal workers equipment.
System 1 is preferable on large area roofs, and system 2 for smaller areas where there are a number of penetrations, attachments etc.
System 1 is made up of standardised pre-profiled bays as shown in fig. 4
System 2 is made up of standardised bays with straight side upstands of 35 and 45 mm, as shown in fig. 5.


Both systems are shown in fig. 2. Each has a special type of clip (see specification for standard components). The height of the standing seam (on both systems) is 25 mm.

Specification of standard components

NedZink Zinc-Titanium 0.80 mm


System 1

Pre-profiled, straight bays (fig. 4)


width between centres 530 mm
length, normal   up to 6 mm





Fixed clip (fig. 3a)
Sliding clip (fig. 3b)


Pre-profiled curved bays radius from 1 m
Non-standard width between centres (min. 300 mm and max. 800 mm) can be supplied on request, and curved bays by agreement.
System 2

Bays with straight side upstands (fig. 5)


width between centres 600 mm     
length, normal 3 m

Non-standard lengths and widths can be supplied on request
Fixed clips (fig. 6a)
Sliding clips (fig. 6b)
Attachment profiles can be supplied on request if the quantity is sufficient.


A single welt pliers, eaves edger and eaves welter are required in addition to normal zinc working tools.


A double standing seam system roof must be fully supported by a substructure. We recommend timber of unplaned boards (not tongue-and-grooved) 20 - 25 mm thick. The boards are assembled about 5 mm apart, except when the pitch exceeds 40°, in which case they may be 100 mm apart (see figs. 7a and 7b).

Ventilation: If the roof has thermal insulation, a cavity should be left under the zinc for ventilation purposes (see NedZink Advice TZ 5).



Marking out
The marking work should be commenced in the centre of the roof area, bay widths being marked to the left and right of this point. A projecting piece is always needed for the verge flashing, so the roof edge can be made. As far as possible, standing seams should not be interrupted for roof penetration structures: this ensures that the optimum benefit is obtained from mechanical folding.


Thermal movement
The bays expand and contract with temperature. This means that the bay length should not exceed 10 m. If the length exceeds 10 m a transverse joint is needed to allow for thermal movement: the actual type depends on the pitch of the roof (see fig. 8). At this joint, part of the profile is removed, to prevent the welt becoming too thick (see fig. 9).


Assembling the bays
The bays are laid from left to right or right to left, as indicated on the substructure. Before the first bay is laid, however, the eaves abutment should be fitted. An example of this is illustrated in figs. 10a and 10b. The first bay has to serve as a verge flashing, it generally does not retain its full width.
Once the bay has been hooked into place, the fixed and sliding clips are attached. The siting at which the fixed clips are attached depends on the pitch of the roof (see fig. 11).

Consult the table in fig. 12 to calculate the distance between the clips for different bay widths and roof heights.

Fig. 12   Number of clips per m² and distance apart as a function of bay width and roof height.


Material thickness 0.80 mm

Bay width

Number of clips per m² and centre–to–centre distances (in mm)


Roof height

Area Roof

20 – 100 m Normal area    
  Verge area    
8 - 20 m Normal area    
  Verge area  
0 - 8 m Normal area    
  Verge area  


500 mm

530 mm

8 – 250

8 - 210

8 – 250

8 - 210



5 - 400

5 - 330

6 - 330

6 - 280



5 - 400

5 - 330

5 - 400

5 - 330


Once the first bay has been laid and the clips have been attached, the next bay is laid alongside it without the use of lateral force with sufficient overhang at the eaves. However if more than one strip is needed between the eaves and the ridge, the whole length form eaves to ridge is laid first, and then a cross welt is produced (see fig. 8). The second bay is laid when this has been completed, beginning at the eaves again.
When this bay is in the correct position, the fixed and sliding clips must be attached, as already described. The normal procedure is for the whole roof to be covered with bays first.
To prevent the bays being blown off the roof, the welt is closed with single welt pliers once every metre, at the same point as a clip.


Once all the bays have been laid, the seams are folded mechanically. The first 20 cm of each seam are folded together manually so mechanical folding can be started.
Than on the standing seam the folding machine works, turned either up or down. A rope is attached to the motor of the machine for safety reasons.
The eaves abutment is produced by the bottom edge of the bay being cut and folded.
A straight chalk line is marked out on the bottom edge of the bay to enable a straight eaves border to be produced. The bay can then be cut as illustrated in fig. 10b.
The eaves edger is used to produce the first fold along the chalk line: this is then closed with the eaves welter.
A different form of eaves finish is shown in fig. 10c: the standing seam is turned down at the eaves.


-    Ridge abutment
The ridge abutment is made by turning down the standing seam with the open welt underneath. Fig. 13 shows details of ridge abutment on an insulated roof with a ventilated cavity. If there is not much room available, the ridge abutment is produced by means of a crimped seam as shown in fig. 14. In this, the pre-profiled side upstand profile is bent back on site to form a straight upstand.

-    Verge flashing profile
The verge flashing profile is formed by turning up the projecting part of the first and last zinc-titanium bays against a verge roll. These bays can be cut to the correct width and the side upstands formed against the roll either on the roof or beforehand. The upstand is at least 55 mm high. The construction is shown in fig. 15. The verge roll can be covered with any kind of profile. Both this capping and the bay upstand are secured with at least three clips per metre, see also fig. 12.

-    Wall abutment
One example of a wall abutment is given in fig. 16. A gap must be allowed for ventilation.

-    Roof penetration
The methods used for ridge abutment, verge flashing attachment and eaves abutment are used here. The zinc-titanium should not be fitted too close to the roof penetration. It must be able to expand and contract freely. Fig. 17 shows an example of a chimney penetrating on a roof.


-    Hip construction
The two roof surfaces are separated by a hip roll. The double standing seam bays are attached to this roll in the same way as for the ridge abutment: see fig. 13, but splayed. Capping is fitted over the wooden hip roll. The upstand against this hip roll must be no less than 55 mm at right angles to the edge of the hip roll. Fig. 18 shows the structure in zinc-titanium.


-    Valley gutter
The valley is the angle between two pitched roofs. The bottom end of the bay is cut splayed, and bent over as shown in the eaves abutment fig. 10b. This bend hooks into the additional clip which is soldered in lengths of e.g. 1 m onto the valley gutter. The valley gutter is secured onto the underlying timber by means of clips (see fig. 19). The distance 'a' depends on the pitch dgr. and may be calculated as follows:



a =  ________ 

          sin a


15dgr ----   a = 200 mm

20dgr ----   a = 160 mm

25dgr ----   a = 130 mm

30dgr ----   a = 110 mm
35dgr ----   a = 100 mm

40dgr ----   a =  90 mm

45dgr ----   a =  80 mm



When the pitch is less than 15dgr, a box gutter must be used in the valley (see fig. 20). The minimum depth of this box gutter is 12 cm.

Facade cladding

When used for façade cladding, the standing seam system likewise requires a ventilation gap behind the zinc-titanium. The working method for a facade corresponds to that for roofing. The single standing seam is used more frequently on facades than on roofs.