Following up on my previous post where I remarked about the workmanship and quality of products used on roofs. Today I want to talk to you about metal roof sheeting, specifically IBR (Inverted Box Rib) and traditional corrugated iron sheeting.
IBR is a square-fluted roof profile and is ideal for large construction projects and is becoming very popular in urban areas as well for flatlets and renovations in residential areas. It is known for its strength, low maintenance requirements and aesthetic appeal making it a popular choice. |
Corrugated metal roof sheeting is the most commonly used S-rib roofing profile for roof sheets. Corrugated sheeting provides efficient water runoff (depending on the gradient) of the roof. It can withstand different weather conditions and enhances the aesthetic appeal of buildings and homes. The gentle wave-like pattern gives an eye-pleasing effect to the senses. |
The rule of supply and demand plays a big role in the cost comparison of these two roofing types. Price drives the market. Beware there are other factors to consider too. These factors include amongst others, the following: The manufacturing process, the thickness of the metal and the correct installation method. Remember “goedkoop is duurkoop”.
The manufacturing process:
How are the metal roof sheets protected against the effect of the elements?
Galvanising: Many people are under the impression that galvanising prevents rust. This is a myth, let me tell you why.
When steel roof sheets are made, they are coated by dipping them into hot molten zinc. The zinc ions bond with the iron molecules in the steel to create a shiny, rust-resistant surface finish. This process is called galvanisation.
Although the sheets are covered with zinc, any scratches, kinks, dents, and/or bends, break the seal that is covering the top layers of iron. For rust to start, all you need is a bit of oxygen. These sheets are often manhandled in transporting and with installation and these scratches and dents occur.
Basic grade 8 science : Iron + Oxygen = Iron Oxide (rust)
Another process used to treat metal sheeting is the Galvalume method where aluminium and silicon is added to the zinc. As the coating dries , patches of aluminium and zinc molecules coalesce into a pattern across the sheet’s surface.
The aluminium areas provide corrosion resistance, while the zinc provides galvanisation protection. The small amount of silicon helps the coating adhere to the underlying metal, even when it is cut or rolled.
Lastly, we have metal sheeting called Chromadek®. Due to Chromadek® being a well-established brand name, the name is being used generically to describe any pre-painted roof sheeting. Authentic Chromadek® sheeting is imprinted with "ArcelorMittal South Africa Chromadek®" at regular intervals to mark it as the genuine colour-coated steel product manufactured by ArcelorMittal South Africa. So if it does not say “Chromadek®” then you do not have the real thing. Genuine Chromadek® consists of a galvanised steel substrate coated with zinc, aluminium and a paint system. It is this combination of metals and paint that gives this type of sheeting its unique long-lasting protection, extended lifespan and enhancing visual appeal.
The longevity of the metal is also influenced by its thickness. Be careful when looking at price and you are comparing prices at various outlets, make sure you check the thickness and length before making the comparison.
Lastly, you need to make sure you know what your contractor is installing on your roof. Ask them about the type of product, its lifespan, the maintenance requirements, and the type of flashing that is going to be installed. Ninety percent of roof leaks and product malfunctions are caused by poor roof installs and incorrect or defective flashing that is being used. Some flashing materials are not compatible with all roof types. Your qualified contractor should know this.
As a certified home and roof inspector, I conduct detailed roof inspections and should you want an unbiased professional opinion of your roof installation, contact me by clicking one of the links below:
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