In order to obtain optimum performance of the
ZINCALUME® steel or COLORBOND® steel
product, correct design and erection is
It is critical that a free drip edge be maintained
for all ZINCALUME® steel and COLORBOND®
steel products. This is to enable moisture to
drain freely from the sheared edge of the steel
product. It is envisaged that a clearance of
15mm should be sufficient for this purpose.
This is particularly important at the base of the
shed or garage wall. Please refer to Figure 1.
Figure 1 –Simple design of free drip edge
The consequence of not maintaining a free drip
edge is accelerated corrosion. This is due to the
retention of moisture at the cut edge of the steel,
when held in contact with other materials.
Bricks, pavers, concrete slabs and even other metallic products will contribute to this
mechanism when installed incorrectly. Please
refer to Figure 2.
Figure 2 – Corrosion due to inappropriate
Erecting the shed prior to the concrete slab
being poured, consequently using the steel
walling as formwork, is not recommended.
The predominant problem associated with this
poor practice is accelerated corrosion due to:
• Contact with wet cement, which is strongly
• Shrinkage of cured concrete enabling the
build-up of dirt and debris in the gap left
between the slab and the wall.
• Failure to maintain a free drip edge as
Gutter design should ensure that moisture is
allowed to drain freely from the roof and not
be allowed to enter the interior of the shed or
garage. Incorrect design can lead to the
corrosion of interior steel components as well
as damage to its contents.