Techniques for processing
For cutting zinc sheets specific metal tools are available to make the job easy and fast. To cut long pieces straight, the straight cutting snips and Pelikan snips are used. For cutting curves, figures and hard to reach places universal tin snips, punch snips with curved blades of genuine shape cutting snips are used. These snips are available in left- and right version. This doesn’t mean left- or right-handedness, but the way the figures are cut so the work piece is not distorted.
For bending zinc sheet with small dimensions one uses seaming pliers, ranging from 40 mm to 1000 mm. Pliers wider than 200 mm are primarily used for bending bays at the ridge and eaves abutments. To adjust the sides a bossing stick or wooden/pvc hammer is used. Never use a steel hammer, because this will stretch the sheet material. Pr-profiling can mainly be done in the workshop with the proper machines.
Suspended gutters and rainwater downpipes are easily manufactured by machines. Bending tools and machines can shape the zinc sheet to the desired round form.
The double standing seam makes it possible for a roof or façade to be covered with preformed, mechanically folded bays, reducing manually folding to a minimum. The preformed bays are supplied in standard sizes and mechanically or manually folded to a single or double standing seam.
The bays are secured to the substructure by means of fixed and sliding clips. The fixed clips secure the bays and the sliding clips permit longitudinal movement. Standardised pre-profiled bays have a seam height of 25 mm.
Apart from the usual zinc worker tools for this systems also are needed:
- the square seam folder
- the twin square seam folder
- the eaves closing jaws
- the eaves edger
The bays expand and contract with temperature. This means that the bay length should not exceed 10 meter. If the length exceeds 10 meter a transverse joint is needed. To allow the thermal movement, the actual type depends on the pitch of the roof. At this joint, part of the profile is removed to prevent the welt becoming too thick.
When used for façade cladding, the standing seam system likewise requires a ventilation cavity behind the titanium zinc. The working method for a façade corresponds to that for roofing. The single standing seam is used more frequently on facades than on roofs.
Screwing, stapling, nailing
When the zinc sheet is attached to the substructure directly, often screws and nails are used. The screws are made of galvanized steel or stainless steel, the nails should be galvanized. Because of the thermal effects on zinc the material will expand and contract. Therefore it is not allowed to fix the sheets directly to the substrate for more than one meter length in total. The other fixings have to be sliding.
A clip is a small strip of zinc, which on one side is nailed (or screwed) on the substructure and on the other side connected with the zinc by interlocking. The zinc sheet can move easily. With vertical or slanted structures a folded attachment is used to prevent sliding downwards. Sometimes the clips are directly soldered to the zinc, such as lozenges. For fixing the standard systems like standing seam and roll cap, clips are designed that can be used as fixed clips and sliding clips to attach these systems to the substrate. For example: the sliding clips of the standing seam system consists of two interlocking parts. For the roll cap system fixed and sliding clips can be used.
Clips are usually made of zinc with the same thickness (or thicker) as the covering. But they can also be made of stainless steel when more strength and stiffness is required. Clips connect the sheets/systems to the substrate. They have to take the forces due to construction weight, wind load and wind suction. These forces depend on the surface (sqm), geographic location and the height of the building. In the technical advice the table rely on information for The Netherlands only.
For fixing gutters, downpipes and cappings that are not directly mounted on the substructure of a building brackets are applied. Brackets support the structure, sometimes combined with clips. The brackets themselves are attached to the structure with at least two screws (galvanized steel or stainless steel) and are made of galvanized steel. The number of brackets and the distance between the brackets can be derived from the suppliers guidelines or may be determined by strength calculations. The minimum requirements for gutter brackets for The Netherlands are described in NEN 7065.
Manufacturing clips and brackets
Standardized clips and brackets can be purchased through wholesalers. Different sizes must be made from drawings. Zinc clips can be made from remaining strips of zinc sheets, which are used for roof and gutter. The minimum width of a zinc clip is 40 mm and the minimum thickness is 0.80 mm. Often the clips are cut to size on the building size during assembly.
For brackets the material is a steel strip with a width of 30 mm and a thickness between 5 and 10 mm, depending on the required strength of the bracket. Normally the gutter brackets are hot dip galvanized and for The Netherlands must meet EN 1462. The form of the gutter brackets is determined by the roof gutter, just as the manner of attachment.
The form of the standard and non-standard gutter brackets must be adjusted to the form of the wall plate, the required slope, the pitch of the roof and the position of the gutter to be installed (back height higher than the front height).