To keep the timber out of direct contact with the ground or slab. A post set straight into concrete, or standing on wet ground, holds moisture at exactly the point carrying the load — and that is where posts fail.

A support lifts the post clear, lets water drain away and lets air move around the base.

Most are named post size × shaft length. A U-Cup Post Support 100×300mm suits a 100mm post and has a 300mm shaft — it is not for a 100×300mm timber. This is the single most common misread.

Bolt-down anchors use post size × plate thickness × height, so a 90mm×4mm×110mm suits a 90mm post, has a 4mm plate and stands 110mm high.

Fish Tail supports are width × thickness × length — a 50×6×400 is 50mm wide, 6mm thick and 400mm long.

As a guide to what we carry:

• 75mm posts — U-Cup Post Support and U-Cup Stirrup, in shafts from 150mm to 600mm.
• 90mm and 100mm posts — the widest choice: U-Cup, T-Blade, Tornado high-wind anchors, L-Stirrup, and bolt-down anchors.
• 115mm and 125mm posts — U-Cup, bolt-down anchors, T-Blade Heavy Duty and Tornado.
• 140mm and 150mm posts — U-Cup, T-Blade Stirrup Heavy Duty, L-Stirrup and Tornado.

Tell us your post size and how it is being fixed and we will confirm the right one before you order.

The shaft length is decided by how the support is installed, not by the post.

Short shafts (75–150mm) are for bolting down onto existing concrete. Long shafts (300–600mm) are for setting into a concrete footing, where the shaft provides the embedment.

The embedment your footing needs depends on the structure, the loads and the site — take it from the design rather than picking the longest one available.

The most common type. The post sits down into a steel cup and bolts through it, so the cup is visible around the base of the post.

It is the straightforward, well-proven choice for decks, pergolas, carports and verandahs, and it is the widest part of our range — post sizes from 75mm up to 150mm, with shafts from 75mm to 600mm, plus a no-shaft version for fixing flat.

It comes down to whether your footing already exists.

U-Cup Stirrup — the shaft is set into the concrete as the footing is poured. For new work. We stock 75mm stirrups in 150, 200, 300, 450 and 600mm shafts.

U-Cup Bolt-On-Concrete — a base plate that bolts onto an existing slab or footing with M12 anchors. For retrofitting. We stock 70, 90, 100, 115 and 140mm post sizes, including a heavy 140mm×8mm×180mm.

If you are pouring the footing anyway, the stirrup is generally the stronger and simpler connection.

Instead of a cup around the outside of the post, a T-Blade is a steel blade that slots into a saw cut in the base of the post and bolts through.

The appeal is appearance. Almost nothing shows — the post appears to sit directly on the footing, with no steel cup wrapped around it. On an exposed deck or a feature pergola where the posts are part of the look, it is a much cleaner detail than a U-Cup.

The trade-off is that the post has to be accurately cut to take the blade, so it is less forgiving to install.

• Standard T-Blade Post Support — 90mm post, in 200, 300, 450 and 600mm shafts, plus a 300mm shaft version.
• T-Blade Adjustable — Heavy Duty, in 90 and 115 adjusting 220–360mm, and 150 adjusting 270–470mm.
• T-Blade Stirrup Heavy Duty — 115×600mm, 150×600mm and 200×600mm galvanised.
• T-Blade Extra HD Surface Mount — 150mm and 200mm, for fixing to a finished surface.
• Bolt On T-Blade — plus a BOTB cover that conceals the bolt-on base for a tidier finish.

The T-Blade, Bolt On T-Blade and BOTB cover are also available in 316 stainless.

When the finished height is not fixed at the time the footing goes in, or when you are levelling several posts across uneven ground.

The T-Blade Heavy Duty adjustable range gives you 220–360mm on the 90 and 115, and 270–470mm on the 150. That range lets you pour footings first and set the exact post heights afterwards, rather than trying to get every footing perfect.

The heavy-duty anchor for structures where uplift is part of the design — carports, patios, verandahs and anything roofed.

We stock the Tuff Post Anchor High Wind range in M12: 90mm and 100mm posts in 300, 400, 450 and 600mm heights; 115mm and 125mm in 600mm; and 140mm in 450 and 600mm. Also available in 316 stainless.

Choose it from the structural design, not because a bigger anchor feels safer. Wind classification, roof area, post spacing, footing design and the load path all feed into it — have a roofed or elevated structure confirmed by a suitably qualified building professional or structural engineer.

A heavy-duty support with a rod stem rather than a flat shaft, where the post needs to be held off a footing with a strong single-rod embedment.

We stock it for 90mm and 140mm posts, with a 50mm rod stem in 300mm and 450mm lengths, in cartons of 3 and 6.

A flat steel plate with a split, splayed base — the fish tail — that keys into the concrete as the footing is poured. The post bolts onto the plate above ground.

We stock 50×6×400mm and 50×6×600mm M12, plus heavy-duty 65×8×600mm, 65×8×800mm and 75×10×600mm in thicker plate for bigger loads.

A lighter, more economical support for smaller posts and lighter structures — garden structures, screens, light pergolas and fencing.

We stock the Angle Type Stirrup 90×130mm and Angle Type Post Supports in 200, 300, 450 and 600mm shafts, in cartons of 5 and 10. The carton quantities make them worth looking at where you have a run of posts to do.

Near the coast, yes. Salt air carries a long way inland, and a corroded post base is the hardest thing on the whole structure to replace.

We carry 316 marine grade across the Tornado high-wind anchors, T-Blade, Bolt On T-Blade, the BOTB cover and the U-Cup Bolt-On-Concrete. Everything else is hot-dip galvanised, which is the right choice away from the coast.

Keep the bolts in the same material family as the support — mixing galvanised and stainless in a wet connection accelerates corrosion of the galvanised part.

No. A post support is a connection, not a structural design. The post section, the footing, the bolts and the load path all have to be worked out together.

A bigger support does not compensate for an undersized post or an inadequate footing. For load-bearing decks, pergolas, carports and anything roofed, have the design confirmed by a suitably qualified building professional or structural engineer.

Yes. Send us your post size, whether the support is going into a new footing or bolting to existing concrete, the height you need, whether the structure is roofed, and whether the site is coastal. That is enough for us to narrow it to the right product and quantity.

We also supply the Merbau posts themselves, plus the bolts, brackets and structural timber that go with them. Browse the full Decking Wood QLD range of post supports, timber, decking and hardware.