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Currently planning to replace my old low steel balustrade with merabau post (90mm) rail and baluster.
The balcony floor is concrete (120mm) and I am planning to fix post brackets down
into the surface.
I’ve purchased the “VuePro concealed post support 90mm” (T shape) to improve aesthetics however looking at the specifications for the product it doesn’t specifically list that it is suitable for balustrade posts.
1. Are the concealed T post supports suitable for balustrade post install?
2. Is the longer version more suitable?
3. Is another option better for balustrade? I.e C/U bracket
Welcome to the Bunnings Workshop community @svensseasnakes. It's sensational to have you join us, and many thanks for your question about post supports.
While these concealed post supports are compliant with AS 1720 for timber design, they are only rated to resist vertical loads such as wind uplift and dead load. They are not designed to provide lateral stability.
Balustrade posts are governed by horizontal and point loads from people leaning or pushing against them, so lateral stability is essential. Because these supports are not rated or tested for lateral or moment loads, they are only suitable for balustrade applications if the post is braced, say at the top, and fixed to another structural member there. Otherwise, these supports are best used for decorative or non-structural posts, such as screens or pergola posts, where lateral loads are managed by other means.
That said, this is similar to most brackets, where lateral stability needs to be achieved through connection to other structures. Could you let us know whether these are free-standing posts or if they are connected to the house somehow?
Please let me know if you have any questions.
Mitchell
Is there a handrail that connects them, @svensseasnakes, that itself ties back into a structure? At the base of a post, almost all common post supports, including those for 90 × 90 posts, are designed to take vertical loads and resist uplift, not lateral or bending loads. This isn’t unique to one type of support, it applies to stirrups, saddles, and bolt-down anchors generally. Structurally, they behave like a pinned connection, so the post can rotate under sideways force.
That’s why spec sheets often say they’re “not suitable for lateral loads unless braced”. The bracing they’re referring to is the structure around the post, not the post support itself. In something like a balcony handrail, the lateral strength comes from the posts being tied together by a rigid handrail and, importantly, that handrail being fixed back into a solid structure. The load is transferred through the rail into the building, not resisted at the post base.
So yes, post supports can be suitable for handrails and similar applications, but only as part of a complete, braced system. On their own, all surface-mounted post supports share this limitation unless they’re specifically engineered to resist moment loads.
Mitchell
Thanks Mitchell,
Yes I plan for there to be a handrail to connect at all posts together. This can be tied into building at a single point on the return length as the balustrade layout is L shaped.
It does not have the opportunity to tie into the building at any other point.
I've attached the below sketch for further clarity with approximate measurements
And on the other end, is the balcony handrail connected to the handrail on the stairs, which connects to the structural stringers @svensseasnakes?
You might need to run your plan past a builder to get their thoughts on whether the balustrade will be well supported and comply with regulations.
Let me also tag @Nailbag for his thoughts.
Mitchell
It is important to look at the balustrade as a complete system rather than focusing on an individual post in isolation @svensseasnakes. A single post fixed to concrete with a surface-mounted post support is essentially freestanding, and if you were to push it back and forth at the top, the leverage created could eventually work the fixings loose. That is exactly why manufacturers state that these brackets do not provide lateral or moment resistance on their own.
Once you introduce a second post fixed in the same way and then rigidly connect those two posts together with a handrail, the behaviour changes significantly. Any sideways load applied to one post is now shared with the other post through the handrail. That connection provides lateral reinforcement because the force is distributed across multiple fixings instead of being concentrated at a single base. As more posts are added and tied together, the overall resistance to lateral movement increases accordingly.
In your case, the L shaped layout further improves rigidity. The corner post and return section add a lot of stiffness because the structure is no longer acting in a single straight line. Loads are resisted in two directions, which makes the balustrade much harder to rack or twist. The fact that the handrail then continues down the stairs and is ultimately fixed into a solid brick and concrete stair structure provides an additional point of restraint, which effectively anchors the whole system.
So while the post supports themselves do not resist lateral forces as individual components, when they are used as part of a continuous, well connected balustrade with multiple posts, a rigid handrail, a corner return, and a connection back into the building, the cumulative effect is a stable and structurally sound installation. This is exactly how most surface mounted timber balustrades are designed to work in practice.
As always, ensuring correct spacing, solid fixings into the concrete, and compliance with the relevant balustrade height and load requirements is essential, but from a structural behaviour point of view, you are on the right track.
Mitchell
