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Zip-Tek 420 is a unique concealed fix system commonly known as a standing seam system. This is one of the only concealed fix systems where the sheet can be tapered, as well as smooth curved. It is also the only concealed system that can be reversed curved.

It is recommended that Zip-Tek 420™ sheeting should be laid by an approved contractor in strict accordance with the manufacturer's specifications.


When using a GRS (Brownbuilt™) Approved Contractor, a five-year guarantee of on-site workmanship and water tightness may be issued after approval by Global Roofing Solutions.

Sheet Lengths

Zip-Tek 420 is available, ex-factory, in sheet lengths limited only by transport restrictions; normal loads 12.5m and abnormal loads 18.6m.


Longer lengths can be milled on-site, eliminating end laps, which are not recommended.

End lapping negates the concealed fix concept and no water tightness guarantee can be issued.

End lapping, due to corrosion, reduces the life expectancy of the roof.

Tapered sheets

Tapered Zip-Tek 420 sheets have become increasingly significant for roofing applications as they can be formed into a diverse range of shapes. The minimum and maximum cover widths range between 280mm and 600mm.  (When cover widths exceed 450mm consult GRS as additional support will be required).

The minimum sheet length is to be 1500mm long. Tapered Zip-Tek 420 sheets have to be installed on the roof by following the precise instructions laid down in the relevant installation plan. It is advisable to check the actual dimensions of the substructure before producing the tapered sheets.



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The profile shall be roll-formed with two ribs at centres not exceeding 424mm and a cover width not exceeding 424mm.

These will include a male and female rib with capillary action breaks. The male head shall be smaller than the female head.

When seamed, the minimum sheet depth shall be 68mm.

The Zip-Tek 420™ sheets shall be fixed to every purlin using a patented halter. The halter must be secured using suitable fasteners as detailed in the GRS Installation manual. The female rib must be mechanically seamed using a seaming machine 420 over the entire length of the sheet.


Zip-Tek 420™ can be Bullnosed cranked from a minimum radius of 1000m. Reverse cranking is not possible.


Zip-Tek 420 can be sprung to a minimum radius of 36m (convex) and 60m (concave), with internal spans of purlins at 1.5m max.



Both springing and curving of Zip-Tek 420 can result in stresses in the material, resulting in oil canning. Mechanical curving will eliminate the majority of these effects. Care must be taken in checking the structure line of the curve carefully,  plus ensuring that all halters are in line. Any discrepancy will affect the line of halters, resulting in poor aesthetics.


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