This tube is pre galvanized round stock for structural work: scaffolding, farm frames and general construction. It arrives straight and uniform, ready to be cut, bent and bolted on site, and because it is zinc coated before it reaches the job the ends and the bore are protected rather than only the outside. The same stock goes into our greenhouse frames, so a farm running both uses one grade of tube across the whole site and repairs a bent member with a section from the same supply.
Round steel tube does the load carrying work on most farm structures, and it does it in places where nobody looks again once the frame is up: inside a scaffold leg, inside a greenhouse hoop, inside a brace that has been in the ground for five seasons. The grade and the coating are what decide whether it is still doing that work years later.
Round section is chosen where a member has to bend or where it has to take load from any direction. It bends evenly rather than flattening on one face, which is why it is used for the hoops of a greenhouse and the legs of a scaffold, and it has no corner to hold water where the run-off collects. The same reasoning applies to farm shelters, shade frames and fence structures.
Stocking one grade across a site is the other half of the argument. A tube that has been bent by machinery or by a falling limb can be replaced with a section that matches, and nobody has to rework the joint geometry around a piece that behaves differently. Frames built from the same stock are shown on the film greenhouse range page on this site, and the structure side of the same stock is set out on the structure greenhouse page.
Pre galvanizing puts the zinc on the tube before it is cut to length, so the coating covers the outside of the stock and the cut ends are the only exposed faces on the finished member. On a scaffold or a farm frame those ends are the ones that stand at ground level or at a joint, which is exactly where rust starts on an uncoated tube.
The practical consequence is about handling rather than specification. A cut end is bare steel, and in a wet or coastal location it is worth treating at the time the member is cut rather than at the end of the build. The same discipline applies to a nicked surface: the coating is doing the work, so a scratch is touched up where it happens.
The tube is supplied to be worked, and it can be cut, bent, welded or bolted depending on how the structure goes together. Where the joint is bolted the coating survives the assembly and the joint can be taken apart again, which is the arrangement most farm frames use for the members that are likely to be hit. Welding burns the coating back along the tube, so welded joints are the ones to watch at the first season check.
Bending is done cold for the radii used on a greenhouse hoop and a scaffold standard, and it is worth setting the bender to the section rather than to the job, because a tube that is over-bent and straightened has already lost some of what it was bought for.
The table below is the standard stock. Size, section and length are set to the drawing.
| Type | Round |
| Standard | ASTM |
| Technique | Hot rolled |
| Surface treatment | Pre galvanized |
| Alloy or not | Non-alloy |
| Shape | Round bar stock |
| Uses | Scaffolding, construction frames and greenhouse structures |
| Delivery time | Set out in the quotation for each order |
Tube is delivered in bundles, so unloading and stacking are part of the job rather than an afterthought. Bundles are lifted with slings rather than forks wherever possible, because a fork that slides under a bundle drags the coating off the bottom layer, and the coating is the reason the tube was bought galvanized.
On site the stock should be kept off the ground on bearers and covered, so water does not sit in the tube ends through the wet season. That applies to the finished structure as much as the stock: a member that is damaged during assembly is treated at that point, because it is where the rust will start. A frame that uses this stock is described in the ASTM A53 galvanized steel pipe for greenhouse frames.
This stock is used for scaffold standards and ledgers, for greenhouse hoops, purlins and braces, and for farm shelters, shade frames and fence structures. It suits contractors who need one grade of tube across a site, growers building or extending a frame from a drawing, and operations that want a structure they can repair with a section rather than replace as a set.
Standards for steel products and for the coating systems applied to them are published by BSI. Horticulture and construction industry reporting for growers and contractors is published by HortWeek. The specification that matters is the one that still suits the job ten years from now.
The zinc is applied to the tube before it is cut to length, so the outside of the stock is coated and the cut ends are the exposed faces on the finished member. Those ends are usually at ground level or at a joint, which is where rust starts first.
It can, but welding burns the coating back along the tube, so welded joints are the ones to inspect at the first season check. A bolted joint leaves the coating intact and can also be taken apart, which is why most farm frames are bolted.
A galvanized steel structure is rated for 15 to 20 years under normal conditions, with the fixings and any cut ends checked as part of the season service.
We provide a 10 year structural warranty and a 5 year anti-corrosion warranty on the galvanized steel. Details are set out in the contract for each project.
Send the sizes and quantities you need, the application and the delivery port. We reply with a quotation and the delivery schedule.
