Published by

Joyce Tan


November 10, 2016

Galvanised Steel vs Non-Galvanised Steel for Trellis

Exterior Renovation Tips

While we were having a photo shoot at a customer’s roof terrace recently, our Technical Director, Gareth, explained to me why we use Galvanised Steel to construct the trellis for our customer.

Amazing Roof Terrace Trellis
Amazing Roof Terrace Trellis

Galvanised Steel is steel that has been hot-dipped in molten zinc. The zinc ends up coating all surfaces of the steel and prevents rust from forming.

When building trellises, it’s especially important to use Galvanised Steel as trellises are outdoor structures and are exposed to rain.

A cheaper option (cheaper upfront) would be to use steel and then paint it over to prevent rust. The surface of the metal needs to be prepared carefully before painting. Any rust that has formed on the steel prior to painting needs to be thoroughly removed.

Like these pipes that we saw outside a workshop. The shiny ones on the left are Galvanised Steel and the ones on the right (not so shiny ones…) are non-galvanised. These were left outdoors for a few days, guess which ones stayed the same and which ones started to rust.

Galvanised vs Non-galvanised Steel
Galvanised vs Non-galvanised Steel

In fact, rusty non-galvanised pipes are not that uncommon.

Why, you may ask. You simply have to build the trellis structure and paint it over before rust sets in.

There are a few issues here. Firstly, it’s almost impossible to ensure that the steel bars that come out from the supplier’s factory are rust-free. Once these bars have rust on them, it’s a virtual nightmare trying to sand them off.

Secondly, in Singapore, thunderstorms can happen at a moment’s notice. There would hardly be time to cover up the trellis structure before the rain comes. The moisture in the air is also hard to contend with.

Non-galvanised steel trellises may seem cheaper in the short term, but cost more in maintenance in the longer term. It may even need to be overhauled ultimately. All in all, it seems penny-wise and pound foolish to use non-galvanised steel for trellis jobs. With non-galvanised steel, it’s not a matter of whether rust will occur, it’s more like a matter of when.

Modern galvanised Steel Trellis in Singapore
Modern Galvanised Steel Trellis in Singapore

We totally understand that outdoor structures like trellises and pergolas need to be hardy and withstand the outdoor element without adding maintenance burden on busy homeowners, which is why we use Galvanised Steel in our trellis jobs.

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