VM ZINC® BASICS

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Transversal junctions

When the length of the roof slope exceeds the maximum recommended length, it is necessary to join the sheets using transverse junctions. Several techniques exist depending on the pitch of the roof.

These include:

Step (or drip): for pitches of 3° (5%) or more
The step height will be a minimum of 8 cm for standing seam.

Double welt: for pitches of 11° (20%) or more
The double welt can be used for pitches of 11° and above. The minimum length of the overlap is 200 mm*The dimensions can vary due to the projected expansion and/or contraction based on the conditions at the time of installation., with a securing clip at the top. Depending on climatic conditions such as wind and rain, the overlap should be increased. The VM ZINC® fixed clip (#1 in diagram below) should be soldered onto the zinc sheet, not fastened to it.

Single welt: for pitches > 25° (47%) or more
The single welt or single lock cross-welt with an overlap of 51 mm*The dimensions can vary due to the projected expansion and/or contraction based on the conditions at the time of installation. can be adopted for pitches greater than 25° (42%) in the standing seam technique.

Umicore Building Products recommends using the double welt over the single welt for standing seam techniques as it provides greater water resistance.