Timber fencing with steel posts

Traditional timber fencing is built using timber posts, however a growing trend in the Sydney market is the use of steel posts with timber fences.
The first steel post/ timber combinations used round posts which were more readily available. You may see older timber fences that still have round steel posts. Initially, they were made quite thick for fence building so you will find that most of the round posts are at least 2.5mm thick. Steel posts used in fence building today are generally 50x50mm square posts. Initially, square posts were manufactured with similar thickness to that of round posts.
A relatively new product on the market in Sydney is a 50×50 steel post which is 1.6mm thick and often referred to as light gauge posts. These posts are substantially cheaper than 2.5mm thick posts, which are often referred to as heavy gauge posts.
The cost of a light gauge steel post is approximately $16, whereas a heavy gauge steel post will set you back an average of $28. Over the length of a decent sized fence, the price difference can be quite significant. To complicate things further, the naming of these posts can be deceptive for customers purchasing a fence installation. Always check the thickness of the posts you have been quoted for before booking a job. This will ensure you receive the quality of posts you’re after.
People often ask me what the cost difference is between a standard treated pine post or a steel post. The cost is close to the same for light gauge steel posts and timber posts. Briefly, treated pine posts with rail holes morticed (cut out from post) costs approximately $16. An additional cost of steel posts is that the rails are often bracketed to the post using Z shaped brackets which cost approximately $3 each. This increases the cost of the steel post option by $9 per post when built using brackets. Please see my article “Treated pine posts vs hardwood posts vs steel posts for timber fencing” for more information for the steel versus timber post debate.
So which steel posts are right for you?
Light gauge steel posts are not as strong as Heavy gauge steel posts but it also depends on what you’re attaching to your posts. Fences come in many different styles and timbers and there are some where light gauge steel posts are sufficient to hold the weight of the fence, but also situations where light gauge isn’t enough. With no clear standards for fence post thickness versus the weight of fence; this is a bit of a grey area in fencing. No one likes grey areas so I offer you my opinion based on my experiences, my colleagues and various suppliers who’ve been in the industry for many years:
Treated pine is lighter than hardwood so light gauge steel can be used for treated pine fences up to 1.8m high for standard paling fences. I would not recommend light gauge steel posts for a lapped or lapped and capped treated pine fence. These fences hold one and a half times the weight of a standard paling fence and would not be well supported. In addition light gauge steel posts are not suitable for any hardwood fence jobs over 1.5m in height: the weight is too much for the frame to handle.
When fences are higher than standard and heavier due to materials used, the thickness of the steel or the size of the post should be increased also. The most common size post used in these circumstances is 65x65mm.

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